Acids, Bases and Salts: Class 10 Science Chapter 2 Hinglish mein

Science · Hinglish notes, simulations aur practice · Official NCERT chapter PDF ↗

Published 12 Oct 2026 · Updated 12 Oct 2026

100 min
39 practice questions
25 MCQs

Is chapter mein aap kya seekhenge

Natural, synthetic aur olfactory indicators se acids aur bases mein farak pehchano
Acids aur bases ke metals, carbonates, oxides aur ek doosre ke saath reactions ke word aur balanced equations likho
Samjho ki acids hydronium ions aur bases hydroxide ions sirf paani mein hi dete hain, aur unke solutions electricity kyun conduct karte hain
pH scale se compare karo ki solutions kitne acidic ya basic hain, aur strong aur weak acids mein farak karo
Batao ki body, soil, digestion, tooth decay aur stings mein pH kyun important hai
Predict karo ki salt ka solution acidic, basic ya neutral hoga, aur salts ko families mein group karo
Batao ki sodium hydroxide, bleaching powder, baking soda, washing soda aur Plaster of Paris kaise banaye jaate hain aur kis kaam aate hain
Copper sulphate, washing soda aur gypsum ki madad se water of crystallisation samjhao

NCERT Science Class 10, Chapter 2, pp. 17–36 par based original companion text. Yeh NCERT se juda nahi hai aur NCERT ne ise endorse nahi kiya hai.

Ek badi family feast ka end socho: puris, chhole, achaar aur gulab jamun ki doosri plate. Ek ghante baad koi seene mein jalan ki shikayat karta hai, wahi takleef jise hum aam taur par acidity kehte hain. Tum use kya doge?

Shuru karne se pehle

Inmein se kaun si cheez sach mein jalan kam karegi?

Ek glass lemon sodaEk chammach milk of magnesiaKhatte aam ke achaar ka ek tukda

Answer dekho

Answer (B) Ek chammach milk of magnesia

Milk of magnesia ek mild base hai, isliye woh pet ke extra acid ka kuch hissa cancel kar deta hai. Lemon soda aur aam ka achaar khatte lagte hain kyunki unmein pehle se acids hote hain: woh problem badhayenge, theek nahi karenge.

Tumne shayad ek hi idea se choose kiya: acids aur bases ek doosre ka effect cancel karte hain. Dono se tum pichhli classes mein mil chuke ho. Acids (अम्ल) swaad mein khatte hote hain, jabki bases (क्षारक) kadve hote hain aur chhoone mein sabun jaise lagte hain. Lekin laboratory mein hum kabhi kuch chakhte nahi. Uski jagah hum ek indicator (सूचक) use karte hain: aisa substance jiska colour, ya kabhi-kabhi smell, acid aur base mein alag hota hai.

Litmus sabse mashhoor indicator hai: acid blue litmus ko red kar deta hai, aur base red litmus ko blue kar deta hai. Turmeric (haldi) bhi ek indicator hai. Yeh acids mein yellow rehti hai lekin base mein reddish-brown ho jaati hai. Traditional kumkum isi tarah banta hai: yellow haldi ko lime (chuna) ke saath milaya jaata hai, jo ek base hai, aur mixture gehra red ho jaata hai. Laboratories is list mein man-made (synthetic) indicators bhi jodti hain, jaise methyl orange aur phenolphthalein.

Is chapter mein tum dekhoge ki acids aur bases metals, carbonates, oxides aur ek doosre ke saath kaise react karte hain, aur sabhi acids mein common kya hai. Tum pH scale se bhi miloge, jo naapta hai ki solution kitna acidic hai, aur samudra ke salt ko caustic soda, bleaching powder, baking soda aur washing soda bante hue follow karoge.

2.1 Acids aur Bases ki Chemical Properties ko Samajhna

Acids aur bases ko fairly compare karne ke liye hum laboratory chemicals ke ek hi set ko kai indicators se test karte hain, phir unhe metals, carbonates, oxides aur ek doosre ke saath react karate hain. Patterns par dhyaan do: har acid lagbhag ek jaisa hi behave karta hua niklega.

2.1.1 Laboratory mein Acids aur Bases

School laboratory mein kuch acids aur bases label lagi bottles mein rakhe hote hain. Aam acids hain hydrochloric acid ( $H C l$ ), sulphuric acid ( $H_{2} S O_{4}$ ), nitric acid ( $H N O_{3}$ ) aur acetic acid ( $C H_{3} C O O H$ ), jo vinegar ka acid hai. Aam bases hain sodium hydroxide ( $N a O H$ ), potassium hydroxide ( $K O H$ ), calcium hydroxide ( $C a (O H)_{2}$ ), magnesium hydroxide ( $M g (O H)_{2}$ ) aur ammonium hydroxide ( $N H_{4} O H$ ). Table 2.1 mein har indicator ke apne do colours hain.

Table 2.1Common indicators kaise respond karte hain

	Acid mein	Neutral liquid mein	Base mein
Blue litmus paper	red ho jaata hai	blue rehta hai	blue rehta hai
Red litmus paper	red rehta hai	red rehta hai	blue ho jaata hai
Methyl orange	red	yellow	yellow
Phenolphthalein	colourless	colourless	pink
Turmeric	yellow	yellow	reddish-brown

Dhyaan do ki har indicator sirf do groups ko alag karta hai. Phenolphthalein acid aur paani dono mein colourless hai, isliye yeh bases ko pehchanta hai. Methyl orange paani aur base dono mein yellow hai, isliye yeh acids ko pehchanta hai.Methyl orange lagbhag pH 3 se neeche hi poora red hota hai. Bahut weak acid mein yeh orange, ya yellow bhi, dikhta hai. Litmus acids ko bases se alag karta hai, bas shart yeh hai ki tum paper ke dono colours use karo.

4/4Phenolphthalein base mein pink hai, baaki dono mein colourless.

Fig. 2.1Ek tile, teen liquids, chaar indicators: har colour change liquids ko alag tarah se sort karta hai.NCERT Table 2.1 · p. 18

Ek white spotting tile jismein gaddhon ke teen columns hain, jin par acid, water aur base likha hai, aur chaar rows hain jin par blue litmus, red litmus, methyl orange aur phenolphthalein likha hai. Pehle step mein har gaddha khaali hai. Doosre step mein dono litmus rows bharti hain: blue litmus sirf acid mein red hota hai, aur red litmus sirf base mein blue hota hai. Teesre step mein methyl orange wali row acid mein red aur paani aur base mein yellow dikhati hai. Aakhri step mein phenolphthalein wali row acid aur paani mein colourless aur base mein pink dikhati hai. Har colour uske gaddhe mein shabd ke roop mein likha hai.

Activity 2.1NCERT Activity 2.1 · p. 18

Chemical shelf ka colour test karo

Tumhe chahiye

dilute hydrochloric acid, dilute sulphuric acid aur vinegar
sodium hydroxide solution, lime water aur dilute ammonia solution
distilled water
red aur blue litmus paper, methyl orange aur phenolphthalein
ek white tile ya saat watch-glasses, aur droppers

Pehle guess karo

Tumhe kya lagta hai, lime water mein phenolphthalein kya karega?

pink ho jaayegacolourless rahegared ho jaayega

Har liquid ki ek boond white tile ke apne alag gaddhe mein, ya apne alag watch-glass par daalo, aur uspar label lagao.
Har boond ko blue litmus ki ek nayi strip se chhuao, phir red litmus ki strip se. Koi bhi change note karo.
Boondon ke ek naye set par methyl orange ki ek boond daalo; ek aur naye set par phenolphthalein ki ek boond.
Har colour record karo aur har liquid ke liye tay karo: acid, base ya dono mein se koi nahi?

Table 2.2Indicators ke colours

Liquid	Blue litmus	Red litmus	Methyl orange	Phenolphthalein	Acid, base ya neutral?
Dilute hydrochloric acid
Dilute sulphuric acid
Vinegar (acetic acid)
Sodium hydroxide solution
Lime water
Ammonia solution
Distilled water

Tumhari entries apne aap save hoti hain.

Kuch substances colour ki jagah smell se signal dete hain. Yeh olfactory indicators hain (olfactory ka matlab hai smell ki sense se juda). Pyaaz, vanilla essence aur clove oil ki smell acid mein bani rehti hai lekin base mein chali jaati hai. Aise indicators se woh insaan bhi liquid test kar sakta hai jo colours nahi dekh sakta, ya bilkul nahi dekh sakta.

Activity 2.2NCERT Activity 2.2 · p. 18

Apni naak se test karo

Tumhe chahiye

aadha pyaaz
saaf cotton cloth ya filter paper ki do strips
vanilla essence aur clove oil
dilute hydrochloric acid aur dilute sodium hydroxide solution
chaar test tubes

Pehle guess karo

Pyaaz ki smell wali strip par sodium hydroxide ki ek boond girti hai. Pyaaz ki smell ka kya hota hai?

Woh chali jaati haiWoh aur tez ho jaati haiWoh nahi badalti

Dono strips ko pyaaz ke kate hue hisse se achhi tarah ragdo. Unhe ek ghante ke liye chhote plastic bag mein band kar do taaki woh smell sokh lein.
Dono strips ko soongho. Ek strip par dilute hydrochloric acid ki kuch boondein daalo aur doosri par dilute sodium hydroxide ki. Unhe phir se soongho.
Do test tubes mein dilute acid daalo aur do aur mein dilute sodium hydroxide. Ek acid tube aur ek base tube mein vanilla essence ki ek boond daalo, aur baaki dono mein clove oil ki ek boond.
Har tube ko hilao aur uske upar ki hawa ko haath se apni naak ki taraf hilaakar soongho.

Table 2.3Smell ka test

Indicator	Acid mein smell	Base mein smell
Pyaaz
Vanilla essence
Clove oil

Tumhari entries apne aap save hoti hain.

Quick check

3 mein se 1

Ek colourless liquid phenolphthalein ko pink kar deta hai. Isse liquid ke baare mein kya pata chalta hai?

Yeh acidic haiYeh neutral haiYeh basic hai

Answer dekho

Answer (C) Yeh basic hai

Phenolphthalein sirf base mein pink hota hai. Acid aur neutral liquid mein yeh colourless rehta hai.

Practice · 1 question

Indicators (in-text): answers ke saath

Short answerMediumNCERT in-text Question, p. 18
Teen bina label wali test tubes mein ek acid, ek base aur distilled water hai. Tumhare paas sirf blue litmus paper hai. Tum har liquid ko kaise pehchanoge?
Solution dikhao
AnswerBlue litmus sirf acid mein red hota hai. Us red hui strip ko baaki dono mein dubao: base mein woh phir blue ho jaati hai aur paani mein red rehti hai.
Har tube mein ek blue strip dubao. Sirf acid use red karta hai, to woh tube acid wali hai.
Ab tumhare haath mein ek red strip hai. Use bachi hui do tubes mein dubao. Base mein woh phir blue ho jaati hai; distilled water mein red rehti hai. Is tarah base aur paani bhi pehchaan liye gaye.

2.1.2 Acids aur Bases Metals ke saath Kaise React Karte Hain?

Dilute acid mein zinc ke kuch daane daalo aur metal jaldi hi fizz karne lagta hai. Yeh bubbles ek gas hain, aur agli activity use pehchanti hai.

Activity 2.3NCERT Activity 2.3 · p. 19

Zinc acid ke saath kaun si gas deta hai?

Tumhe chahiye

zinc granules
dilute sulphuric acid, dilute hydrochloric acid aur acetic acid
do test tubes aur ek stand
ek lakdi ki splint aur maachis

Pehle guess karo

Gas ko ek ulti tube mein collect kiya jaata hai, aur uske muh ke paas jalti splint laayi jaati hai. Tumhe kya ummeed hai?

Flame aur tez ho jaati haiFlame chupchaap bujh jaati haiEk chhoti si 'pop' ki awaaz aati hai

Stand mein lagi test tube mein teen-chaar zinc granules daalo. Usmein lagbhag 3 cm gehrai tak dilute sulphuric acid daalo.
Zinc ki surface ko dekho. Ek doosri, khaali test tube ko pehli tube ke muh ke upar lagbhag aadhe minute tak ulta pakdo, taaki gas usmein jama ho jaaye.
Collecting tube ko ulta hi rakhte hue hatao aur uske muh ke paas jalti splint lao. Suno.
Dilute hydrochloric acid ke saath dohrao aur phir acetic acid ke saath. Compare karo ki bubbles kitni tezi se bante hain.

Zinc se bubbles ki dhaar nikalti hai, aur jama hui gas pop ke saath jalti hai: yeh hydrogen hai. Tube ko ulta isliye pakadte hain kyunki hydrogen hawa se bahut halki hai aur upar uthkar usmein chali jaati hai. Hydrochloric acid bhi hydrogen deta hai, aur acetic acid bahut dheere deta hai. Nitric acid ek exception hai: zyada tar metals ke saath yeh hydrogen ki jagah doosri gases deta hai, jaisa tum Chapter 3 mein dekhoge.

3/3Muh par jalti splint: gas pop ke saath jalti hai. Yeh hydrogen hai.

Fig. 2.2Zinc aur dilute acid se hydrogen collect karna, aur use flame se test karna.NCERT Fig. 2.1 · p. 19

Left mein stand mein lagi ek test tube mein dilute sulphuric acid mein zinc granules hain. Pehle step mein zinc se bubbles uthte hain. Doosre step mein ek khaali test tube pehli tube ke muh ke upar ulti pakdi gayi hai, aur gas, jis par hydrogen likha hai, usmein jama hoti hai kyunki woh hawa se halki hai. Teesre step mein ulti tube ko side mein hata diya gaya hai aur uske muh par jalti splint pakdi hai; pop shabd wala ek burst mark test ka result dikhata hai.

Is reaction mein metal acid se hydrogen ko bahar dhakelta hai aur uski jagah le leta hai. Doosra product, zinc sulphate, ek salt (लवण) hai: aisa compound jo tab banta hai jab acid ke hydrogen ki jagah metal aa jaata hai.

\begin{aligned} Z n (s) + H_{2} S O_{4} (a q) \\ \overset{}{\to} Z n S O_{4} (a q) \\ + H_{2} (g) \end{aligned}

(2.1)

Hydrochloric acid ke saath reaction $Z n + 2 H C l \overset{}{\to} Z n C l_{2} + H_{2}$ iski jagah zinc chloride deta hai. Gas wahi hai; sirf salt acid par depend karta hai. General roop mein:

\begin{aligned} acid + metal \\ ⟶ salt + hydrogen \end{aligned}

(2.2)

sodium zincate

\begin{aligned} 2 N a O H (a q) + Z n (s) \\ \overset{}{\to} N a_{2} Z n O_{2} \\ + H_{2} (g) \end{aligned}

(2.3)

Sodium zincate ek alag tarah ka salt hai: ismein metal oxygen ke saath uske negative ion, $Z n O_{2}^{2 -}$ , ke andar pahunch jaata hai. Sirf kuch metals, jaise zinc aur aluminium, bases ke saath is tarah react karte hain. Jaise, iron aur copper sodium hydroxide ke saath bilkul react nahi karte.

2.1.3 Metal Carbonates aur Metal Hydrogencarbonates Acids ke saath Kaise React Karte Hain?

Chutki bhar baking soda par nimbu ka ras nichodo aur usmein turant jhaag ban jaata hai. Baking soda sodium hydrogencarbonate hai; washing soda sodium carbonate hai. Dono compounds ki badi families mein aate hain jo har acid ke saath ek hi tarah react karti hain.

Activity 2.5NCERT Activity 2.5 · p. 20

Fizz, phir lime-water test

Tumhe chahiye

spatula ki nok bhar washing soda (sodium carbonate) aur utna hi baking soda (sodium hydrogencarbonate)
dilute hydrochloric acid
taaza bana, saaf lime water
do boiling tubes, mudi hui delivery tubes wale corks, do test tubes

Pehle guess karo

Fizz karti tubes ki gas ko saaf lime water mein se bubble karaya jaata hai. Tum kya dekhoge?

Lime water doodhiya ho jaata haiLime water blue ho jaata haiKuch nahi badalta

Do boiling tubes par 1 aur 2 label lagao. Tube 1 mein washing soda aur tube 2 mein baking soda daalo.
Har ek mein thoda dilute hydrochloric acid daalo, aur jaldi se delivery tube wala cork laga do.
Har tube ki gas ko ek test tube mein rakhe lime water mein se bubble hone do. Note karo kya hota hai.
Ek lime-water tube mein gas ko kuch minute aur bubble karte raho, aur dhyaan se dekho.

2/3Lime water doodhiya ho jaata hai: insoluble calcium carbonate banta hai.

Fig. 2.3Carbon dioxide ka lime-water test, aur gas lagaataar behti rahe to kya hota hai.NCERT Fig. 2.2 · p. 20

Left mein cork lagi ek boiling tube mein baking soda aur dilute hydrochloric acid hai; ek mudi hui delivery tube gas ko right mein lime water wali test tube tak le jaati hai. Pehle step mein powder fizz karta hai aur lime water saaf hai. Doosre step mein lime water doodhiya hai, jis par calcium carbonate likha hai. Teesre step mein, bahut zyada gas ke baad, lime water phir saaf hai, jis par calcium hydrogencarbonate likha hai, jo ghul jaata hai.

Dono tubes mein reactions yeh hain:

\begin{aligned} N a_{2} C O_{3} + 2 H C l \\ \overset{}{\to} 2 N a C l + H_{2} O \\ + C O_{2} \end{aligned}

(2.4)

\begin{aligned} N a H C O_{3} + H C l \\ \overset{}{\to} N a C l + H_{2} O \\ + C O_{2} \end{aligned}

(2.5)

Carbon dioxide lime water ke calcium hydroxide ke saath react karke calcium carbonate banati hai. Calcium carbonate ghulta nahi, isliye woh ek baarik white precipitate ki tarah dikhta hai jo liquid ko doodhiya bana deta hai:

\begin{aligned} C a (O H)_{2} + C O_{2} \\ \overset{}{\to} C a C O_{3} + H_{2} O \end{aligned}

(2.6)

Aur carbon dioxide milne par precipitate phir ghul jaata hai, kyunki woh calcium hydrogencarbonate mein badal jaata hai, jo paani mein soluble hai:

\begin{aligned} C a C O_{3} + H_{2} O \\ + C O_{2} \\ \overset{}{\to} C a (H C O_{3})_{2} \end{aligned}

(2.7)

Calcium carbonate tumhare chaaron taraf hai: limestone, chalk aur marble isi se bante hain, aur ande ke chhilke aur seepiyan bhi. Isiliye acids marble ki moortiyon aur imaaraton ko dheere-dheere kha jaate hain. Har metal carbonate aur hydrogencarbonate acid ke saath yahi teen tarah ke products deta hai:

\begin{aligned} carbonate + acid \\ ⟶ salt + C O_{2} \\ + water \end{aligned}

(2.8)

2.1.4 Acids aur Bases Ek Doosre ke saath Kaise React Karte Hain?

Acid metal ke saath bhi fizz karta hai aur carbonate ke saath bhi. Lekin jab acid base se milta hai, to kuch hota hua nahi dikhta: na bubbles, na colour. Indicator ki madad se hum reaction dekh paate hain.

Activity 2.6NCERT Activity 2.6 · p. 21

Boondein gino

Tumhe chahiye

dilute sodium hydroxide solution
dropper bottle mein dilute hydrochloric acid
phenolphthalein solution
ek test tube

Pehle guess karo

Tum phenolphthalein se pink hue sodium hydroxide mein boond-boond acid daalte ho. Pink colour ka kya hoga?

Yeh blue ho jaayegaYeh aur gehra ho jaayegaKisi ek boond par yeh gayab ho jaayega

Ek test tube mein lagbhag 2 mL dilute sodium hydroxide daalo, usmein phenolphthalein ki do boondein daalo, aur colour note karo.
Ek-ek boond karke dilute hydrochloric acid daalo, har boond ke baad hilao. Colour gayab hone tak boondein gino.
Ab sodium hydroxide ki ek-do boondein daalo. Kya colour waapas aata hai?

3/4Koi $O H^{-}$ nahi bacha: sirf salt aur paani, isliye colourless.

Fig. 2.4Acid ki har boond hydroxide ions hatati hai; jab koi nahi bachta, to pink chala jaata hai.

Left mein ek test tube hai jiske upar dropper hai; right mein ek panel liquid ke ions dikhata hai. Pehle step mein liquid pink hai aur panel mein bahut saare sodium ions aur hydroxide ions hain. Doosre step mein thoda acid daala gaya hai: hydroxide ions kam hain, water molecules aa gaye hain, aur liquid abhi bhi pink hai. Teesre step mein liquid colourless hai aur panel mein sirf sodium ions, chloride ions aur paani hai. Aakhri step mein base ki ek boond daali gayi hai: kuch hydroxide ions waapas aa gaye hain aur liquid phir pink hai.

Tube mein reaction yeh hai:

\begin{aligned} N a O H + H C l \\ \overset{}{\to} N a C l + H_{2} O \end{aligned}

(2.9)

Definition

Neutralisation reaction

Aisa reaction jismein acid aur base ek doosre ki properties cancel kar dete hain, aur salt aur paani bante hain.

ExampleHydrochloric acid aur sodium hydroxide se sodium chloride (common salt) aur paani bante hain.

\begin{aligned} base + acid \\ ⟶ salt + water \end{aligned}

(2.10)

Example 2.1

Zyada base, zyada acid

Ek test mein, sodium hydroxide solution ke 25 mL ko hydrochloric acid solution ke 15 mL se poori tarah neutralise kiya jaata hai. Usi sodium hydroxide solution ke 40 mL ko neutralise karne ke liye usi acid ka kitna volume chahiye?

Pehle khud try karo. Phir solution ek-ek step karke kholo.

2.1.5 Metallic Oxides ka Acids ke saath Reaction

\begin{aligned} C u O (s) + 2 H C l (a q) \\ \overset{}{\to} C u C l_{2} (a q) \\ + H_{2} O (l) \end{aligned}

(2.11)

Yeh bilkul neutralisation jaisa hai: metal oxide plus acid se salt aur paani milte hain. To metal oxides bases ki tarah behave karte hain, aur hum unhe basic oxides kehte hain. Magnesium oxide, jo magnesium ribbon jalne par bachi white raakh hai (Chapter 1), bhi isi tarah acids mein ghul jaata hai.

\begin{aligned} metal oxide + acid \\ ⟶ salt + water \end{aligned}

(2.12)

2.1.6 Non-metallic Oxide ka Base ke saath Reaction

Agar metal oxides bases ki tarah kaam karte hain, to kya non-metal oxides acids ki tarah kaam karte hain? Yeh test tum bina jaane pehle hi kar chuke ho. Activity 2.5 ke lime-water test mein carbon dioxide ek base, calcium hydroxide, se mili, aur products calcium carbonate aur paani the: ek salt aur paani, bilkul wahi jo ek acid deta. To carbon dioxide, jo non-metal carbon ka oxide hai, acid ki tarah behave karti hai, aur non-metal oxides ko acidic oxides kehte hain. Gaadiyon aur factories se nikli sulphur dioxide aur nitrogen dioxide baarish mein ghulkar acids banati hain, aur isi tarah acid rain banti hai.

5/5Base + non-metal oxide → salt + water. Har baar salt banta hai.

Fig. 2.5Paanch reactions, ek common product: har ek salt banata hai.

Paanch rows wala ek chart, har row mein reactants ke ek pair se products tak ek arrow hai. Step ek mein acid plus metal se salt plus hydrogen milta hai. Step do mein acid plus carbonate se salt plus carbon dioxide plus water judta hai. Step teen mein acid plus base se salt plus water judta hai. Step chaar mein acid plus metal oxide se salt plus water judta hai. Step paanch mein base plus non-metal oxide se salt plus water judta hai, aur product column ka har salt highlight hota hai.

Example 2.2

Poora karo aur balance karo

Har equation ko poora karo aur balance karo, aur reaction ka type batao.

$M g O + H C l \overset{}{\to}$
$K O H + H_{2} S O_{4} \overset{}{\to}$
$N a O H + C O_{2} \overset{}{\to}$

Pehle khud try karo. Phir solution ek-ek step karke kholo.

Practice · 3 questions

Acids aur bases ke reactions (in-text): answers ke saath

Short answerEasyNCERT in-text Questions, p. 22, Q1
Tumhari daadi nimbu ka achaar sirf glass ya ceramic ke jaar mein rakhti hain, kabhi brass ya copper ke bartan mein nahi. Samjhao kyun.
Solution dikhao
AnswerAchaar acidic hai. Samay ke saath acid copper aur brass par attack karta hai aur copper aur zinc ke salts banata hai jo khaane ke liye nuksaandeh hain.
Nimbu ke achaar mein citric acid hota hai. Brass copper aur zinc ka alloy hai. Dinon aur hafton mein, khaas kar hawa ke hone par, acid in metals ke saath react karke copper aur zinc ke salts banata hai.
Yeh salts achaar mein ghul jaate hain, uska swaad bigaad dete hain aur logon ko beemar kar sakte hain. Glass aur ceramic food acids ke saath react nahi karte, isliye woh safe containers hain.
2
Short answerEasyNCERT in-text Questions, p. 22, Q2
Magnesium ribbon ki ek strip dilute sulphuric acid mein daali jaati hai.
1. Nikalne wali gas ka naam batao aur balanced equation likho.
  Solution dikhao
  Gas hydrogen hai.
  $\begin{aligned} M g + H_{2} S O_{4} \\ \overset{}{\to} M g S O_{4} + H_{2} \end{aligned}$
2. Tum is gas ko kaise test karoge?
  Solution dikhao
  Gas ko ulti test tube mein collect karo aur uske muh ke paas jalti splint lao. Gas pop ke saath jalti hai, jo dikhata hai ki yeh hydrogen hai.
Short answerMediumNCERT in-text Questions, p. 22, Q3
Ek white solid X mein dilute nitric acid daalne par fizz hota hai. Gas jalti candle ko bujha deti hai aur lime water ko doodhiya kar deti hai. Ek product calcium nitrate hai. X ko pehchano aur balanced equation likho.
Solution dikhao
AnswerX calcium carbonate hai.
Gas flame bujhaati hai aur lime water ko doodhiya karti hai, isliye yeh carbon dioxide hai. Aisi gas carbonate aur acid se aati hai. Salt calcium nitrate hai, to metal calcium hai: X calcium carbonate, $C a C O_{3}$ , hai.
$\begin{aligned} C a C O_{3} \\ + 2 H N O_{3} \\ \overset{}{\to} C a (N O_{3})_{2} \\ + H_{2} O + C O_{2} \end{aligned}$

2.2 Sabhi Acids aur Sabhi Bases mein Common Kya Hai?

Yeh rahi ek paheli. Glucose ( $C_{6} H_{12} O_{6}$ ), alcohol ( $C_{2} H_{5} O H$ ) aur hydrochloric acid ( $H C l$ ), sabmein hydrogen atoms hain; glucose ke har molecule mein baarah hain. Phir bhi sirf hydrochloric acid khatta lagta hai, litmus ko red karta hai aur zinc ke saath fizz karta hai. To sirf hydrogen hona poori kahani nahi ho sakti. Ek battery aur ek bulb yeh farak dikhate hain.

Activity 2.8NCERT Activity 2.8 · p. 22

Kaun se solutions current le jaate hain?

Tumhe chahiye

ek 6 V battery
holder mein ek torch bulb, ek switch aur connecting wires
do steel drawing pins jo ek sakht card mein se ghusaye gaye hon
ek chhota glass ya beaker
glucose solution, alcohol, dilute hydrochloric acid, dilute sulphuric acid, sodium hydroxide solution aur lime water

Pehle guess karo

Kaun sa liquid bulb ko jalayega?

glucose solutionalcoholdilute hydrochloric acid

Dono drawing pins ko card mein lagbhag 2 cm ki doori par ghusao. Card ko glass par aise rakho ki pins ki nok liquid mein dubi rahe.
Pins, bulb, switch aur battery ko ek hi loop mein jodo.
Baari-baari se har liquid daalo, switch on karo aur bulb ko dekho. Har liquid ke beech glass aur pins ko paani se dho lo.

Table 2.4Kaun se liquids conduct karte hain?

Liquid	Kya bulb jalta hai?
Glucose solution
Alcohol
Dilute hydrochloric acid
Dilute sulphuric acid
Sodium hydroxide solution
Lime water

Tumhari entries apne aap save hoti hain.

2/3Dilute HCl: $H^{+}$ aur $C l^{-}$ ions chalte hain. Bulb jalta hai.

Fig. 2.6Sirf woh liquids circuit poora karte hain jinmein ions hote hain.NCERT Fig. 2.3 · p. 22

Ek battery, ek switch aur ek bulb ek loop mein jude hain, jo liquid ke glass mein dubi do pins par toot jaata hai. Pehle step mein glass mein glucose solution hai jo poore molecules ki tarah dikhaya gaya hai, aur bulb andhera hai. Doosre step mein usmein dilute hydrochloric acid hai, jo opposite pins ki taraf badhte hydrogen ions aur chloride ions ki tarah dikhaya gaya hai, aur bulb jalta hai. Teesre step mein usmein sodium hydroxide solution hai, jo sodium ions aur hydroxide ions ki tarah dikhaya gaya hai, aur bulb phir jalta hai.

Paani mein har acid hydrogen ions, $H^{+}$ , chhodta hai, saath mein ek negative ion jo har acid mein alag hota hai:

Table 2.5Acids paani mein kaun se ions chhodte hain

Acid	Positive ion	Negative ion
$H C l$	$H^{+}$	$C l^{-}$ (chloride)
$H N O_{3}$	$H^{+}$	$N O_{3}^{-}$ (nitrate)
$H_{2} S O_{4}$	$H^{+}$ (do)	$S O_{4}^{2 -}$ (sulphate)
$C H_{3} C O O H$	$H^{+}$	$C H_{3} C O O^{-}$ (acetate)

Positive ion hamesha same hota hai. To solution mein acid jo hydrogen ions banata hai, jinhe $H^{+} (a q)$ likhte hain, wahi use acidic banate hain. Glucose aur alcohol apne hydrogen atoms ko molecules ke andar mazbooti se jode rakhte hain. Woh koi $H^{+}$ ions nahi chhodte, isliye unmein koi acidic properties nahi dikhti. Alkalis ka bhi apna ek common ion hai, jo tum aage dekhoge.

2.2.1 Water Solution mein Acid ya Base ka Kya Hota Hai?

Kya acid ko ions banane ke liye paani chahiye? Room temperature par hydrogen chloride ek gas hai, aur hydrochloric acid bas yahi gas paani mein ghuli hui hai. To hum dry gas ko uske solution se compare kar sakte hain.

Activity 2.9NCERT Activity 2.9 · p. 23

Dry gas, geela paper

Tumhe chahiye

ek spatula solid sodium chloride
concentrated sulphuric acid (sirf teacher ke liye)
cork aur delivery tube wali ek sookhi boiling tube
blue litmus paper ki sookhi aur geeli strips

Pehle guess karo

Hydrogen chloride gas mein blue litmus ki kaun si strip red hogi?

sirf sookhi stripsirf geeli stripdono strips

Tumhare teacher sodium chloride ko ek sookhi boiling tube mein daalkar thoda concentrated sulphuric acid milate hain. Delivery tube se hydrogen chloride gas nikalti hai.
Gas mein blue litmus ki ek sookhi strip pakdo, phir ek geeli strip.
Humid din par gas ko pehle anhydrous calcium chloride se bhari drying tube mein se guzaara jaata hai, taaki woh dry rahe.

2/3Paani hydrogen le leta hai: $H_{3} O^{+}$ aur $C l^{-}$ ions bante hain.

Fig. 2.7Paani hydrogen chloride se hydrogen ions kheench leta hai; paani ke bina koi ions nahi.NCERT Fig. 2.4 · p. 23

Molecules jude hue circles ki tarah dikhaye gaye hain. Pehle step mein hydrogen chloride molecules blue litmus ki sookhi strip ke paas tair rahe hain, jo blue hi rehti hai. Doosre step mein water molecules jodte hain: har hydrogen chloride molecule apna hydrogen ek water molecule ko de deta hai, aur ek hydronium ion aur ek chloride ion bante hain. Teesre step mein strip, jo ab geeli hai aur hydronium ions ko chhoo rahi hai, red ho chuki hai.

Paani hydrogen ko chlorine se door kheench leta hai. Hydrogen ek akele $H^{+}$ ion ki tarah nikalta hai, jo khud akela nahi reh sakta aur turant ek water molecule se jud jaata hai:

\begin{aligned} H C l + H_{2} O \\ \overset{}{\to} H_{3} O^{+} + C l^{-} \end{aligned}

(2.13)

H^{+} + H_{2} O \overset{}{\to} H_{3} O^{+}

(2.14)

Definition

Hydronium ion

$H_{3} O^{+}$ ion, jo tab banta hai jab ek hydrogen ion ek water molecule se jud jaata hai. Paani mein $H^{+}$ isi roop mein rehta hai, isliye $H^{+} (a q)$ aur $H_{3} O^{+}$ ka matlab ek hi hai.

Bases jab ghulte hain, to hydroxide ions, $O H^{-}$ , chhodte hain:

\begin{aligned} N a O H \\ \overset{}{\to} N a^{+} + O H^{-} \end{aligned}

(2.15)

Potassium hydroxide bhi isi tarah $K^{+}$ aur $O H^{-}$ ions chhodta hai, aur magnesium hydroxide ki har ghuli unit ek $M g^{2 +}$ ion aur do $O H^{-}$ ions chhodti hai.

Definition

Alkali

Aisa base jo paani mein ghulkar hydroxide ions ( $O H^{-}$ ) deta hai.

ExampleSodium hydroxide aur potassium hydroxide alkalis hain.

Ab neutralisation bahut simple lagta hai. Kisi bhi acid ko $H X$ aur kisi bhi base ko $M O H$ likho:

\begin{aligned} H X + M O H \\ \overset{}{\to} M X + H_{2} O \end{aligned}

(2.16)

$M^{+}$ aur $X^{-}$ ions solution mein salt ke roop mein reh jaate hain. Asli change yeh hai ki hydrogen ions aur hydroxide ions judkar paani banate hain:

\begin{aligned} H^{+} (a q) + O H^{-} (a q) \\ \overset{}{\to} H_{2} O (l) \end{aligned}

(2.17)

Activity 2.10NCERT Activity 2.10 · p. 24

Kya paani ke saath milane par heat nikalti hai?

Tumhe chahiye

do chhote beakers, har ek lagbhag ek chauthai paani se bhara
ek thermometer
concentrated sulphuric acid (sirf teacher ke liye)
sodium hydroxide ki kuch pellets

Pehle guess karo

Acid daalne par thermometer kya dikhayega?

temperature mein girawatkoi change nahitemperature mein badhat

Paani ka temperature note karo.
Tumhare teacher dheere se concentrated sulphuric acid ki kuch boondein daalte hain aur beaker ko ghumaate hain.
Temperature phir se note karo aur beaker ke bahar haath lagakar mehsoos karo.
Naye paani aur sodium hydroxide ki kuch pellets ke saath dohrao.

Table 2.6Milane par temperature change

Paani mein kya daala	Pehle (°C)	Baad mein (°C)
Concentrated sulphuric acid
Sodium hydroxide pellets

Tumhari entries apne aap save hoti hain.

3/3Wahi ions zyada paani mein: har millilitre mein kam.

Fig. 2.8Dilution unhi ions ko zyada paani mein phaila deta hai, isliye har millilitre mein kam ions hote hain.NCERT Fig. 2.5 · p. 24

Pehle step mein concentrated acid ka ek chhota flask dikhaya gaya hai jismein chhote volume mein bahut saare ions bhare hain. Doosre step mein acid ko ek patli dhaar mein glass rod ke saath paani ke ek bade beaker mein daala ja raha hai, hilaane ke liye ek muda hua arrow aur kuch heat marks ke saath. Teesre step mein utne hi ions kahin bade volume mein phaile hain, aur ek box ek millilitre ko mark karta hai jismein ab bahut kam ions hain.

Definition

Dilution

Acid ya base mein paani milana. Wahi $H_{3} O^{+}$ ya $O H^{-}$ ions bade volume mein phail jaate hain, isliye har millilitre mein woh kam hote hain.

Quick check

4 mein se 1

Dilute hydrochloric acid electricity conduct kyun karta hai, jabki glucose solution nahi karta?

Iske molecules current le jaate hainYeh paani mein ions banata haiGlucose mein hydrogen nahi hota

Answer dekho

Answer (B) Yeh paani mein ions banata hai

Liquid mein se current ke liye chalte hue ions chahiye. HCl paani mein

H_{3} O^{+}

aur

C l^{-}

mein toot jaata hai. Glucose mein hydrogen to hota hai, lekin woh ions nahi banata.

Practice · 6 questions

Paani mein ions (in-text): answers ke saath

Short answerEasyNCERT in-text Questions, p. 25, Q1
Ethanol ( $C_{2} H_{5} O H$ ) aur nitric acid ( $H N O_{3}$ ) dono mein hydrogen hai. Sirf nitric acid ka solution acid ki tarah behave kyun karta hai?
Solution dikhao
AnswerNitric acid paani mein $H^{+} (a q)$ ions chhodta hai; ethanol nahi chhodta.
Acidic properties solution ke hydrogen ions se aati hain. Nitric acid paani mein $H^{+} (a q)$ ( $H_{3} O^{+}$ ke roop mein) aur $N O_{3}^{-}$ ions mein toot jaata hai.
Ethanol mein hydrogen atoms molecules ke andar jude rehte hain, isliye uske solution mein koi extra hydrogen ions nahi hote aur koi acidic properties nahi dikhti.
Short answerEasyNCERT in-text Questions, p. 25, Q2
Ek student likhta hai: 'Acid solution electricity conduct karta hai kyunki uske molecules wires ke beech chalte hain.' Is statement ko sahi karo.
Solution dikhao
AnswerYeh conduct karta hai kyunki acid paani mein ions banata hai, aur chalte hue ions current le jaate hain.
Neutral molecules current nahi le ja sakte. Paani mein acid ions mein toot jaata hai, jaise HCl se $H_{3} O^{+}$ aur $C l^{-}$ . Yeh charged ions wires ki taraf chalte hain, aur unka chalna hi current hai.
Short answerMediumNCERT in-text Questions, p. 25, Q3
Sookhe blue litmus ki ek strip dry hydrogen chloride gas ke jar mein pakdi jaati hai aur blue hi rehti hai. Kaun sa simple change use red kar dega, aur kyun?
Solution dikhao
AnswerLitmus strip ko geela karo. Paani hone par HCl $H_{3} O^{+}$ ions banata hai, aur yeh litmus ko red kar dete hain.
Dry hydrogen chloride molecules ke roop mein hota hai, ions ke roop mein nahi, isliye woh acid ki tarah kaam nahi kar sakta. Agar strip geeli ho, to gas uspar ke paani mein ghul jaati hai, aur bane hue hydronium ions litmus ko red kar dete hain:
$\begin{aligned} H C l + H_{2} O \\ \overset{}{\to} H_{3} O^{+} + C l^{-} \end{aligned}$
Short answerMediumNCERT in-text Questions, p. 25, Q4
Ek lab assistant ko concentrated acid se dilute sulphuric acid banana hai. Use acid aur paani kis order mein milane chahiye? Ulta karne par kya gadbad ho sakti hai?
Solution dikhao
AnswerAcid ko dheere-dheere paani mein hilaate hue daalo. Acid mein paani daalne se woh ubalkar acid uchhaal sakta hai, aur glass chatak sakta hai.
Milana bahut exothermic hai. Jab acid ko dheere-dheere zyada paani mein daala jaata hai, to paani heat sokh leta hai aur mixture bas garam hota hai.
Agar concentrated acid par paani daala jaaye, to thoda sa paani turant ubal jaata hai. Mixture bahar uchhalkar jala sakta hai, aur achaanak heating se container chatak sakta hai.
Quick answerEasyNCERT in-text Questions, p. 25, Q5
Hydrochloric acid ke solution mein utna hi volume paani milaya jaata hai. $H_{3} O^{+}$ ions ka concentration …
do guna ho jaata hailagbhag aadha ho jaata haisame rehta hai
Answer dekho
Answer (B) lagbhag aadha ho jaata hai
Utne hi hydronium ions do gune volume mein phail jaate hain, isliye unka concentration lagbhag aadha ho jaata hai.
Quick answerEasyNCERT in-text Questions, p. 25, Q6
Potassium hydroxide solution mein potassium hydroxide ki aur pellets ghulayi jaati hain. $O H^{-}$ ions ka concentration …
badhta haighatta haisame rehta hai
Answer dekho
Answer (A) badhta hai
KOH ki har extra unit lagbhag usi volume mein ek aur $O H^{-}$ ion chhodti hai, isliye concentration badhta hai.

2.3 Acid ya Base Solutions Kitne Strong Hote Hain?

Litmus sirf ek sawaal ka jawaab deta hai: acid ya base? Yeh nimbu ke ras aur battery acid mein farak nahi bata sakta. Chemists acidity ko pH scale par naapte hain, jo aam taur par 0 se 14 tak chalta hai aur teen rules follow karta hai:

pH 7 neutral hai, jaise pure water.
7 se neeche acidic hai. pH jitna kam, solution mein utne zyada hydronium ions.
7 se upar basic hai. pH jitna zyada, solution mein utne zyada hydroxide ions.

Direction par dhyaan do: scale hydrogen ions ke ulta chalta hai, isliye zyada $H_{3} O^{+}$ ka matlab kam pH. Ek unit ka har step das guna change hai. pH 3 wale solution mein pH 4 wale se das guna, aur pH 5 wale se sau guna hydrogen ions hote hain. (Letter p Potenz se aaya hai, jo German mein power ko kehte hain.)

pH padhne ke liye hum universal indicator use karte hain, jo kai indicators ka mixture hai aur step by step colour badalta hai: acids ke liye red, orange aur yellow, neutral ke paas green, aur bases ke liye blue se violet. Isme bhigoye paper strips laboratory mein pH naapne ka sabse tez tareeka hain.

Definition

pH scale

Ek scale, aam taur par 0 se 14 tak, jo batata hai ki solution kitna acidic ya basic hai. pH 7 neutral hai, 7 se neeche acidic aur 7 se upar basic; kam pH ka matlab zyada hydrogen ions.

4/4Baking soda (8.3), milk of magnesia (10.5) aur lime water (12.4) basic hain.

Fig. 2.9pH scale par roz ki cheezein. Colours universal indicator ka sirf mota-mota andaaza hain.NCERT Fig. 2.6 · p. 25

0 se 14 tak numbered ek horizontal bar bands mein rangi hai: acidic end par red aur orange, phir yellow, 7 ke aaspaas green, phir basic end par blue aur violet. Pehle step mein bar ke neeche arrows zyada hydrogen ions ke liye left aur zyada hydroxide ions ke liye right point karte hain. Doosre step mein nimbu ka ras pH 2 ke paas aur tamatar ka ras pH 4 ke paas mark hai. Teesre step mein pure water pH 7 par mark hai, jis par neutral likha hai. Aakhri step mein baking soda solution pH 8.3 ke paas, milk of magnesia 10.5 ke paas aur lime water 12.4 ke paas mark hai.

InteractivepH explorer

0 se 14 tak ek pH scale, mote taur par universal-indicator colours mein ranga hua, jis par ek marker chalta hai. Ek slider pH ko 0.1 ke steps mein set karta hai, aur buttons substances par jump karte hain jaise dilute hydrochloric acid, stomach acid, nimbu ka ras, vinegar, tamatar ka ras, black coffee, saaf baarish, doodh, pure water, blood, samudra ka paani, baking soda solution, soap solution, milk of magnesia, washing soda solution, lime water aur dilute sodium hydroxide. Readouts pH dikhate hain, yeh ki solution strongly ya weakly acidic hai, neutral hai, ya weakly ya strongly basic hai, aur usmein pure water se kitne guna zyada ya kam hydrogen ions hain. Paanch swatches us colour ka naam batate hain jo us pH par blue litmus, red litmus, methyl orange, phenolphthalein aur universal indicator dikhayenge, aur ek note context deta hai, jaise kab tooth enamel par attack hoga, kab baarish acid rain maani jaayegi, ya kab koi liquid corrosive hai.

Fig. 2.10Koi roz ki cheez chuno ya slider ko drag karo. Uska pH dekho, pure water ke comparison mein usmein kitne hydrogen ions hain, aur paanch indicators kya dikhayenge.

Example 2.3

Do solutions ko compare karna

Nimbu ke ras ka pH lagbhag 2 hai aur black coffee ka lagbhag 5. (a) Kismein zyada hydrogen ions hain, aur kitne guna zyada? (b) Har ek mein methyl orange kaun sa colour dikhayega? (Methyl orange pH 3.1 se neeche red aur pH 4.4 se upar yellow hota hai.)

Pehle khud try karo. Phir solution ek-ek step karke kholo.

Activity 2.11NCERT Activity 2.11 · p. 26

Apne aaspaas ki cheezon ka pH naapo

Tumhe chahiye

universal indicator paper aur uska colour chart
table mein diye liquids ke chhote samples
har sample ke liye ek saaf dropper ya glass rod

Har sample ki ek boond pH paper ke naye tukde par daalo.
Kuch seconds ke andar colour ko chart se milao aur pH note karo.
Tay karo ki har sample acidic, neutral ya basic hai.

Table 2.7Roz ke liquids ka pH

Sample	pH paper ka colour	pH (lagbhag)	Acidic, neutral ya basic?
Nimbu ka ras
Buttermilk (chaas)
Soda water
Bina doodh ki chai
Nal ka paani
Paani mein toothpaste
Soap solution
Baking soda solution

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Kya kam pH ka matlab hamesha strong acid hai? Poori tarah nahi. Hydrochloric acid aur acetic acid ko same concentration par lo. Lagbhag har HCl molecule ions mein toot jaata hai, lekin acetic acid ke sirf thode se molecules hi tootte hain, isliye acetic acid solution mein bahut kam hydrogen ions hote hain. Isliye hydrochloric acid ek strong acid hai, aur acetic acid ek weak acid hai. Hydrochloric, sulphuric aur nitric acids strong hain; acetic, citric, lactic aur carbonic acids weak hain. Isi tarah, sodium hydroxide aur potassium hydroxide strong bases hain, jabki ammonium hydroxide ek weak base hai.

2/2HCl poora toot jaata hai; acetic acid bas thoda sa tootta hai.

Fig. 2.11Same concentration, lekin hydrogen ions ki sankhya mein bahut farak.

Do beakers aamne-saamne, jin par hydrochloric acid aur acetic acid likha hai. Pehle step mein har beaker mein aath acid molecules hain jo jude hue pairs ki tarah dikhaye gaye hain, aur label hai same amount. Doosre step mein hydrochloric acid beaker ke saare aath molecules hydrogen ions aur chloride ions mein toot gaye hain, jabki acetic acid beaker mein sirf ek molecule toota hai aur saat poore bache hain. Labels par strong acid, many ions, aur weak acid, few ions likha hai.

Definition

Strong acid

Aisa acid jo paani mein lagbhag poori tarah ions mein toot jaata hai, jaise hydrochloric acid. Weak acid, jaise acetic acid, sirf thoda tootta hai, isliye same concentration par kam hydrogen ions deta hai.

Strong aur concentrated ek baat nahi hai. Ek balti paani mein hydrochloric acid ki kuch boondein ek strong acid ka dilute solution banati hain. Yeh phir bhi strong hai, kyunki jo thoda sa acid hai woh poori tarah ions mein toot chuka hai.

2.3.1 Roz ki Zindagi mein pH ka Mahatva

pH aur living things

Living things pH ko lekar bahut nakhrebaaz hote hain. Tumhara blood pH 7.4 ke bahut paas rakha jaata hai, aur body ki chemistry sirf ek patli range mein, lagbhag 7.0 se 7.8 tak, kaam karti hai. Isse bahar thoda sa shift bhi insaan ko gambhir roop se beemar kar deta hai.

Baarish naturally thodi acidic hoti hai, lagbhag pH 5.6, kyunki woh hawa se thodi carbon dioxide ghol leti hai. Jab dhuen se nikle sulphur aur nitrogen ke oxides use isse zyada acidic bana dete hain, to hum use acid rain kehte hain. Acid rain se bhari jheelon mein machhliyon ke ande nahi phootte aur kai paani ke jaanwar khatam ho jaate hain, kyunki unki body ko bhi, hamari tarah, steady pH chahiye.

Soil ka pH

Plants ko bhi sahi pH chahiye. Zyada tar crops neutral ke paas, lagbhag pH 6 se 7.5 wali soil mein sabse achhi ugti hain. Chai ki jhaadiyon ko acidic soil pasand hai, yeh ek wajah hai ki woh Assam aur Darjeeling ki pahaadi dhalaanon par khoob ugti hain. Kisaan apni soil ka treatment karne se pehle use test karte hain. Bahut zyada acidic soil ko ek base se treat kiya jaata hai: quicklime (calcium oxide), slaked lime (calcium hydroxide) ya powdered chalk (calcium carbonate).

Activity 2.12NCERT Activity 2.12 · p. 27

Apne paas ki soil test karo

Tumhe chahiye

do-teen jagahon ki soil (ek garden bed, ek khet, ek sadak ka kinara)
test tubes aur paani
filter paper aur ek funnel
universal indicator paper

Ek soil sample ka ek chammach ek test tube mein daalo, usse lagbhag teen guna paani ke saath, aur achhi tarah hilao.
Use baithne do, phir matmaile paani ko ek saaf tube mein filter karo.
Saaf filtrate ko universal indicator paper se test karo aur pH note karo.
Baaki samples ke liye dohrao. Note karo ki har sample jahan se aaya, wahan kaun se plants ugte hain.

Table 2.8Soil ka pH

Sample	Kahan se aaya	pH (lagbhag)	Wahan ugne wale plants
1
2
3

Tumhari entries apne aap save hoti hain.

Hamare digestive system mein pH

Kisi antacid ka label padho aur aam taur par tumhe usmein ek base milega: magnesium hydroxide (jo milk of magnesia ke naam se bikta hai) ya sodium hydrogencarbonate. Koi dawai base kyun hogi? Kyunki jo problem woh theek karti hai woh ek acid hai. Tumhara pet khaana todne aur germs ko maarne ke liye lagbhag pH 1.5 se 3.5 par hydrochloric acid chhodta hai. Mucus ki ek layer pet ki deewar ko usse bachati hai. Bhaari ya masaledaar khaana zyada acid bana sakta hai, jo jalan aur irritation karta hai. Ek mild base extra acid ko neutralise kar deta hai, isiliye shuru ke sawaal ka sahi jawaab milk of magnesia tha:

\begin{aligned} M g (O H)_{2} + 2 H C l \\ \overset{}{\to} M g C l_{2} + 2 H_{2} O \end{aligned}

(2.18)

pH aur tooth decay

Fig. 2.12 mein meetha khaane ke baad apne muh ka pH follow karo. Tumhare daanton ki chipchipi layer mein rehne wale bacteria kuch hi minutes mein sugar ko ferment karke acids bana dete hain, aur pH gir jaata hai. Har daant ki bahari layer, enamel, calcium hydroxyapatite hai, jo ek calcium phosphate mineral hai aur tumhari body ka banaya sabse sakht material hai. Sirf paani use nahi ghol sakta, lekin acid ghol sakta hai: lagbhag pH 5.5 se neeche usmein se calcium nikalna shuru ho jaata hai.

3/3Saliva dheere-dheere acid ko neutralise karta hai; lagbhag 45 minutes mein pH normal ho jaata hai.

Fig. 2.12Har meetha snack muh ke pH mein ek dip shuru karta hai. Shaded hissa woh samay hai jab enamel par attack ho raha hota hai.

Muh ke pH ka graph, 4 se 8 tak, time ke against, khaane se pehle se snack ke 60 minutes baad tak. pH 5.5 par ek dashed line par likha hai enamel dissolves below. Pehle step mein khaane se pehle curve lagbhag 6.8 par flat hai. Doosre step mein time zero par meetha snack khaaya jaata hai aur das minute ke andar curve lagbhag pH 5 tak gir jaata hai; 5.5 se neeche wala hissa shaded hai. Teesre step mein lagbhag 25 minutes baad curve 5.5 se upar chadh jaata hai aur lagbhag 45 minutes tak 6.8 par pahunch jaata hai, kyunki saliva acid ko neutralise karta hai.

Har meetha snack ek naya dip shuru karta hai, isliye din bhar kutar-kutar khaana ek baar ki treat se daanton ke liye zyada bura hai. Khaane ke baad kulla ya brush karne se bacteria ka khaana hat jaata hai, aur zyada tar toothpastes thode basic hote hain, isliye woh acid ko neutralise bhi karte hain.

Chemicals se apni raksha

Kuch jaanwar aur plants chemistry se apni raksha karte hain. Aam ke pedon par patton ke ghonsle banane wali laal weaver cheentiyan kaatti hain aur ghaav mein methanoic acid (formic acid) chhodti hain. Nettle plants yahi acid khokhle baalon mein rakhte hain jo tumhari skin mein toot jaate hain. Madhumakkhi ka dank bhi acidic zehar chhod jaata hai. Kyunki gunehgaar ek acid hai, isliye ek mild base aaraam deta hai: us jagah par lagaya gaya baking soda ka paste.

Table 2.9Nature mein milne wale kuch acidsNCERT Table 2.3 · p. 28

Kahan milta hai	Acid
Nimbu, santara	citric acid
Imli, angoor	tartaric acid
Dahi, chaas	lactic acid
Vinegar	acetic acid
Tamatar, palak	oxalic acid
Seb	malic acid
Amla (Indian gooseberry)	ascorbic acid (vitamin C)
Cheenti ka kaatna, nettle ka dank	methanoic acid

Practice · 4 questions

pH scale (in-text): answers ke saath

1
Short answerMediumNCERT in-text Questions, p. 28, Q1
Solution X ka pH 9 hai, aur solution Y ka pH 5 hai.
1. Kis solution mein zyada hydrogen ions hain?
  XY
  Answer dekho
  Answer (B) Y
  Y ka pH kam hai, isliye usmein zyada $H^{+}$ ions hain.
2. Kaun sa acidic hai aur kaun sa basic?
  Solution dikhao
  Y (pH 5, 7 se neeche) acidic hai. X (pH 9, 7 se upar) basic hai.
3. Usmein kitne guna zyada hydrogen ions hain?
  Answer dekho
  Answer 10000
  Farak 9 − 5 = 4 units hai, isliye $10^{4} = 10 000$ guna.
Quick answerEasyNCERT in-text Questions, p. 28, Q2
Jaise-jaise solution mein $H^{+} (a q)$ ions ka concentration badhta hai, solution …
zyada basic hota hai, pH badhta haizyada acidic hota hai, pH ghatta haizyada acidic hota hai, pH badhta hai
Answer dekho
Answer (B) zyada acidic hota hai, pH ghatta hai
Zyada hydrogen ions solution ko zyada acidic banate hain, aur pH hydrogen-ion concentration ke ulta chalta hai, isliye pH girta hai.
Short answerMediumNCERT in-text Questions, p. 28, Q3
Pure water mein, aur lime water mein bhi, kuch $H^{+} (a q)$ ions hote hain. To phir lime water ko basic kyun kehte hain?
Solution dikhao
AnswerLime water mein hydroxide ions hydrogen ions se kahin zyada hote hain, isliye woh base ki tarah behave karta hai.
Har water solution mein kuch hydrogen ions aur kuch hydroxide ions hote hain. Pure water mein dono barabar hote hain, isliye woh neutral (pH 7) hai.
Lime water mein calcium hydroxide bahut saare $O H^{-}$ ions jod deta hai, isliye woh $H^{+}$ ions se kahin zyada ho jaate hain. Isliye solution basic hai, aur uska pH lagbhag 12 hai.
Short answerMediumNCERT in-text Questions, p. 28, Q4
Chai ke bagaan ke paas ke ek khet ke soil test mein pH 4.2 aata hai. Kisaan gehun ugaana chahta hai, jise neutral ke paas wali soil pasand hai. Woh kya mila sakta hai, aur kyun?
Solution dikhao
AnswerQuicklime, slaked lime ya powdered chalk: yeh bases extra acid ko neutralise karke pH badhate hain.
Gehun ke liye pH 4.2 bahut acidic hai. Base milane se soil ka kuch acid neutralise hota hai aur uska pH neutral ki taraf badhta hai.
Sahi bases hain quicklime (calcium oxide), slaked lime (calcium hydroxide) ya powdered chalk (calcium carbonate).

2.4 Salts ke baare mein aur

Is poore chapter mein salts baar-baar aaye hain: zinc aur acid se zinc sulphate, neutralisation se sodium chloride, lime water mein calcium carbonate. Ab khud salts ko dekhte hain: unke naam kaise rakhe jaate hain aur unhe kaise group kiya jaata hai, unke solutions kitne acidic ya basic hote hain, aur kuch important salts kaise banaye aur use kiye jaate hain.

2.4.1 Salts ki Family

Salt ke do hisse hote hain: base se aaya ek positive ion (metal ion, ya ammonium ion $N H_{4}^{+}$ ) aur acid se aaya ek negative ion. Negative ion naam ka doosra hissa deta hai: chlorides hydrochloric acid se aate hain, sulphates sulphuric acid se, nitrates nitric acid se, carbonates carbonic acid se aur acetates acetic acid se. Chemists salts ko families mein baantte hain, kuch surnames ki tarah: har sodium salt ke naam mein sodium hota hai, aur har chloride ke naam mein chloride. To har salt ek saath do families mein aata hai; potassium chloride potassium salt bhi hai aur chloride bhi.

Activity 2.13NCERT Activity 2.13 · p. 28

Salts ko families mein baanto

Har salt ka formula likho aur us acid aur base ka naam batao jisse woh ban sakta hai. Phir salts ko families mein baanto.

Table 2.10Salts aur unke parents

Salt	Formula	Acid	Base
Potassium nitrate
Calcium chloride
Zinc sulphate
Ammonium nitrate
Magnesium chloride
Sodium sulphate
Potassium chloride
Calcium carbonate

Tumhari entries apne aap save hoti hain.

2.4.2 Salts ka pH

Kya saare salts neutral hote hain? Common salt to hai, lekin kai doosre nahi hain.

Activity 2.14NCERT Activity 2.14 · p. 29

Kya salt solutions neutral hote hain?

Tumhe chahiye

potassium chloride, sodium sulphate, ammonium chloride, copper sulphate, sodium carbonate aur sodium hydrogencarbonate, har ek ki chutki bhar
distilled water aur chhe test tubes
red aur blue litmus paper, universal indicator paper

Pehle guess karo

Kya in sabhi salt solutions ka pH 7 hoga?

Nahi: kuch acidic hain aur kuch basicHaan: salts hamesha neutral hote hainNahi: har salt solution acidic hota hai

Har salt ki chutki bhar lagbhag 5 mL distilled water mein ghol do. (Nal ka paani khud neutral na ho, aisa ho sakta hai.)
Har solution ko litmus paper ke dono colours se aur universal indicator paper se test karo.
pH note karo aur us acid aur base ka naam likho jisse har salt bana hai.

Table 2.11Salt solutions ka pH

Salt	pH	Parent acid	Parent base	Acidic, basic ya neutral?
Potassium chloride
Sodium sulphate
Ammonium chloride
Copper sulphate
Sodium carbonate
Sodium hydrogencarbonate

Tumhari entries apne aap save hoti hain.

Table 2.12Salt solution ka pH kya tay karta hai

Kisse bana	Examples	Solution	pH
strong acid + strong base	$K C l$ , $N a_{2} S O_{4}$ , $N a C l$	neutral	7
strong acid + weak base	$N H_{4} C l$ , $C u S O_{4}$	acidic	7 se neeche
weak acid + strong base	$N a_{2} C O_{3}$ , $N a H C O_{3}$	basic	7 se upar

Rule yaad rakhna aasaan hai: salt ka solution apne stronger parent ki taraf jhukta hai. Jab dono parents strong hon, to woh ek doosre ko balance kar dete hain aur salt neutral hota hai. Copper sulphate strong sulphuric acid aur weak copper hydroxide se bana hai, isliye uska solution acidic hai. Sodium carbonate strong sodium hydroxide aur weak carbonic acid se bana hai, isliye uska solution basic hai.

Quick check

2 mein se 1

Inmein se kaun se salts paani mein acidic solution dete hain?

N H_{4} C l

K N O_{3}

C u S O_{4}

N a_{2} C O_{3}

Saare sahi options chuno

Answer dekho

Answer

(A) $N H_{4} C l$
(C) $C u S O_{4}$

N H_{4} C l

aur

C u S O_{4}

strong acid aur weak base se bane hain, isliye acidic hain.

K N O_{3}

neutral hai (dono parents strong) aur

N a_{2} C O_{3}

basic hai (weak acid, strong base).

2.4.3 Common Salt se Chemicals

Sodium chloride, jo hydrochloric acid aur sodium hydroxide ka neutral salt hai, wahi namak hai jo tumhari khaane ki table par hota hai. Yeh aata kahan se hai? India ka zyada tar namak samudra se aata hai. Gujarat aur Tamil Nadu ke coasts par samudra ka paani uthle pans mein bhara jaata hai, dhoop paani ko udaa deti hai, aur crystals ko rake se safed dheron mein jama kiya jaata hai.

Kuch namak zameen se khodkar bhi nikala jaata hai. Laakhon saal pehle uthle samudra sookh gaye aur namak ki moti layers chhod gaye jo baad mein zameen mein dab gayin. Aaj inhe rock salt ki tarah mine kiya jaata hai, jiske bade crystals impurities ki wajah se aksar pink ya brown rang ke hote hain; vrat mein use hone wala pink sendha namak rock salt hi hai. India mein Himachal Pradesh ke Mandi mein rock-salt mines hain.

Common salt chemical industry ke liye ek raw material bhi hai. Fig. 2.13 dikhata hai ki isse sodium hydroxide, chlorine, hydrogen, bleaching powder, baking soda aur washing soda kaise bante hain.

5/5Baking soda ko garam karo, phir paani ke saath crystallise karo: washing soda.

Fig. 2.13Ek sasta raw material, chhe kaam ke chemicals.

Sabse upar common salt, sodium chloride, hai. Doosre step mein electrolysis of brine likha ek arrow teen boxes tak jaata hai: sodium hydroxide, chlorine aur hydrogen. Teesre step mein chlorine se ek arrow, jis par plus dry slaked lime likha hai, bleaching powder tak jaata hai. Chauthe step mein common salt se ek doosri branch, jis par plus ammonia, carbon dioxide aur water likha hai, baking soda, yaani sodium hydrogencarbonate, tak jaati hai. Aakhri step mein heat likha ek arrow baking soda se sodium carbonate tak jaata hai, aur plus ten water likha ek aur arrow washing soda tak.

Sodium hydroxide

Factories sodium hydroxide brine ko electrolyse karke banati hain, jo paani mein common salt ka strong solution hai. Teen products ek saath nikalte hain, aur unmein se do is method ko naam dete hain, chlor-alkali process: chlorine aur ek alkali, sodium hydroxide.

\begin{aligned} 2 N a C l + 2 H_{2} O \\ \overset{e l e c t r i c i t y}{\to} 2 N a O H \\ + C l_{2} + H_{2} \end{aligned}

(2.19)

Fig. 2.14 mein dono electrodes ko dekho. Positive electrode (anode) chlorine chhodta hai, negative electrode (cathode) hydrogen chhodta hai, aur cathode ke aaspaas ka liquid sodium hydroxide solution ban jaata hai. Industry mein in sabka kuch na kuch use hai.

3/3Cathode ke paas phenolphthalein pink ho jaata hai: wahan NaOH bana hai.

Fig. 2.14Chhote scale par chlor-alkali process.NCERT Fig. 2.8 · p. 30

Brine se bhari ek U-shaped tube ki har bhuja mein ek carbon electrode hai, jo battery se juda hai: left electrode positive hai, yaani anode, aur right negative hai, yaani cathode. Pehle step mein switch khula hai aur brine mein sodium ions aur chloride ions hain. Doosre step mein current behta hai: anode par chlorine gas ke bubbles aur cathode par hydrogen gas ke bubbles uthte hain. Teesre step mein phenolphthalein ki ek boond cathode ke aaspaas ke liquid ko pink kar deti hai, jis par likha hai sodium hydroxide forms here.

Compare

Teeno products ke uses

Hydrogen

fuel, rocket fuel bhi
vegetable oils ko jamaakar vanaspati banana
fertilisers ke liye ammonia banana

Chlorine

peene ke paani aur swimming pools ko disinfect karna
PVC pipes banana
bleaches, disinfectants aur pesticides

Sodium hydroxide

soaps aur detergents
paper banana
artificial fibres jaise rayon
metals se grease hatana

Bleaching powder

Chlor-alkali process se mili chlorine ko dry slaked lime ke upar se guzaarkar bleaching powder banaya jaata hai:

\begin{aligned} 2 C a (O H)_{2} + 2 C l_{2} \\ \overset{}{\to} C a (C l O)_{2} \\ + C a C l_{2} + 2 H_{2} O \end{aligned}

(2.20)

Iska active ingredient calcium hypochlorite hai, isliye hum ise short mein $C a (C l O)_{2}$ likhte hain, halaanki dukaanon mein bikne wala powder kai calcium compounds ka mixture hota hai. (Purani kitaabein ise $C a O C l_{2}$ likhti hain.) Isse chlorine ki smell aati hai.

Bleaching powder peene ke paani ko disinfect karta hai: kuon, gaon ke tankon aur water supplies mein thoda sa daala jaata hai, khaas kar baadh ke baad. Textile mills ise cotton aur linen ko safed karne ke liye, paper mills wood pulp ko bleach karne ke liye, aur laundries kapdon ko safed karne ke liye use karti hain. Chemical industries ise oxidising agent ki tarah bhi use karti hain.

Baking soda

Baking soda sodium hydrogencarbonate, $N a H C O_{3}$ , hai, jise sodium bicarbonate bhi kehte hain. Indian kitchens mein yeh bhaturas aur dhoklas ko phulaata hai, aur paani mein chutki bhar daalne se chhole ubalne par jaldi gal jaate hain. Yeh sodium chloride, paani, carbon dioxide aur ammonia se banta hai:

\begin{aligned} N a C l + H_{2} O \\ + C O_{2} + N H_{3} \\ \overset{}{\to} N H_{4} C l \\ + N a H C O_{3} \end{aligned}

(2.21)

Iska solution bas halka basic hai, lagbhag pH 8.3, aur yeh skin ko nahi jalata, isliye thodi maatra khaayi ja sakti hai aur acids ko safely neutralise karne mein use ho sakti hai. Garam karne par, jaise garam tawe par, yeh toot jaata hai:

\begin{aligned} 2 N a H C O_{3} \\ \overset{h e a t}{\to} N a_{2} C O_{3} \\ + H_{2} O + C O_{2} \end{aligned}

(2.22)

Baking soda ke uses:

Baking powder. Baking soda ko tartaric acid jaise ek weak khaane laayak acid ke saath milaya jaata hai. Jab mixture geela ya garam hota hai, to dono react karke carbon dioxide chhodte hain, jiske bubbles cakes, bread aur dhokla ko phula dete hain aur unhe halka aur spongy bana dete hain (equation 2.23). Acidity ke liye bikne wala fruit salt bhi baking soda aur citric acid ka aisa hi mixture hai.
Antacid. Paani mein thodi si dose pet ke extra acid ko khatam kar deti hai.
Soda–acid fire extinguishers. Extinguisher ke andar yeh ek acid se milta hai aur carbon dioxide ki ek dhaar banata hai (Group activity II dekho).

baking powder

\begin{aligned} N a H C O_{3} + H^{+} \\ \overset{}{\to} N a^{+} + C O_{2} \\ + H_{2} O \end{aligned}

(2.23)

Washing soda

Washing soda woh sodium carbonate hai jo paani se crystallise hua hai, aur jiski har unit se das water molecules jude hain. Sodium carbonate khud baking soda ko garam karke mil sakta hai (equation 2.22). Iska solution baking soda ke solution se kahin zyada strongly basic hai, lagbhag pH 11.5.

washing soda

\begin{aligned} N a_{2} C O_{3} + 10 H_{2} O \\ \overset{}{\to} N a_{2} C O_{3} \cdot 10 H_{2} O \end{aligned}

(2.24)

Ek sookhe dikhne wale crystal mein das water molecules? Section 2.4.4 samjhata hai ki aisa kaise ho sakta hai.

Washing soda hard water ko soft karta hai: yeh ghule hue calcium aur magnesium salts ko insoluble carbonates mein badalkar permanent hardness hata deta hai, taaki sabun phir se jhaag de. Yeh ghar mein chiknaai wale bartanon, tiles aur naaliyon ki safaai ke kaam bhi aata hai. Industry sodium carbonate se glass, sabun aur paper banati hai, aur doosre sodium compounds jaise borax bhi.

Example 2.4

Compounds ko pehchano

Ek white powder X ko dhokla ke ghol mein milaya jaata hai taaki woh phool jaaye. Sookhi tube mein garam karne par X ek white solid Y, paani, aur ek gas Z deta hai jo lime water ko doodhiya kar deti hai. Y ko paani mein gholkar crystallise karne par ek salt milta hai jo hard water ko soft karne ke kaam aata hai. X, Y, Z aur salt ko pehchano, aur equations likho.

Pehle khud try karo. Phir solution ek-ek step karke kholo.

Quick check

4 mein se 1

Chlor-alkali process mein anode par kaun si gas nikalti hai?

hydrogenchlorineoxygen

Answer dekho

Answer (B) chlorine

Chloride ions positive electrode (anode) par electrons chhod dete hain aur chlorine banate hain. Hydrogen cathode par banti hai.

2.4.4 Kya Salts ke Crystals Sach mein Sookhe Hote Hain?

Copper sulphate ke crystals dekhne aur chhoone mein bilkul sookhe lagte hain. Phir bhi unhe garam karo to paani nikalta hai.

Activity 2.15NCERT Activity 2.15 · p. 32

Sookhe crystals se paani

Tumhe chahiye

blue copper sulphate ke kuch crystals
ek sookhi boiling tube aur ek test-tube holder
ek burner
paani wala ek dropper

Pehle guess karo

Garam karne ke baad crystals kis colour ke ho jaayenge, tumhe kya lagta hai?

whitegehra bluegreen

Sookhi tube ko holder se pakdo, tircha aur logon se door point karte hue, aur kuch crystals ko dheere se garam karo.
Crystals ka colour dekho, aur tube ke thande muh ke paas boondein dhoondho.
Tube ko thanda hone do. Phir powder par paani ki do-teen boondein daalo aur tube ke neeche ke hisse ko chhuo.

2/3Crystals white ho jaate hain; muh ke paas paani condense hota hai.

Fig. 2.15Garam karne se water of crystallisation nikal jaata hai; paani daalne se woh waapas aa jaata hai.NCERT Fig. 2.9 · p. 32

Tirchi pakdi ek boiling tube ke neeche crystals hain. Pehle step mein crystals blue hain aur un par CuSO4 5H2O likha hai. Doosre step mein ek flame tube ko garam karti hai: crystals white powder ban gaye hain, jis par anhydrous likha hai, aur thande muh ke paas paani ki boondein dikhti hain. Teesre step mein ek dropper thande powder mein paani daalta hai, jo phir blue ho jaata hai, aur heat marks dikhate hain ki tube garam ho rahi hai.

Definition

Water of crystallisation

Salt ke crystals mein ek fixed ratio mein bane hue water molecules: salt ki har formula unit ke liye ek tay sankhya.

ExampleCopper sulphate ke crystals mein paanch hote hain: $C u S O_{4} \cdot 5 H_{2} O$ .

To $C u S O_{4} \cdot 5 H_{2} O$ mein dot ka matlab hai ki crystal ki har formula unit ke saath paanch water molecules hain. Washing soda, $N a_{2} C O_{3} \cdot 10 H_{2} O$ , mein das hote hain. Aise crystals geele nahi hote: paani crystal ke andar bana hota hai aur tumhara haath geela nahi karta. Garam karne se woh nikal jaata hai:

blue se white

\begin{aligned} C u S O_{4} \cdot 5 H_{2} O \\ \overset{h e a t}{\to} C u S O_{4} + 5 H_{2} O \end{aligned}

(2.25)

White mineral gypsum, $C a S O_{4} \cdot 2 H_{2} O$ , mein calcium sulphate ki har unit ke liye do water molecules hote hain. India apna zyada tar gypsum Rajasthan mein mine karta hai, aur yeh ek bahut kaam ke powder ka raw material hai.

Plaster of Paris

Gypsum ko lagbhag 373 K tak garam karo aur woh apne paani ka kuch hissa kho deta hai, aur calcium sulphate hemihydrate ban jaata hai, jise Plaster of Paris ke naam se zyada jaana jaata hai:

\begin{aligned} C a S O_{4} \cdot 2 H_{2} O \\ \overset{373 K}{\to} C a S O_{4} \cdot \frac{1}{2} H_{2} O \\ + \frac{3}{2} H_{2} O \end{aligned}

(2.26)

Plaster of Paris ek white powder hai. Ise paani mein milao aur kuch hi minutes mein yeh phir gypsum ban jaata hai aur patthar jaisa sakht jam jaata hai:

\begin{aligned} C a S O_{4} \cdot \frac{1}{2} H_{2} O \\ + \frac{3}{2} H_{2} O \\ \overset{}{\to} C a S O_{4} \cdot 2 H_{2} O \end{aligned}

(2.27)

Koi bhi crystal kisi cheez ka aadha molecule nahi rakhta. Iski jagah pairs mein gino: har do calcium sulphate units ke liye ek water molecule hai, $(C a S O_{4})_{2} \cdot H_{2} O$ , jo average mein har unit ke liye aadha banta hai.

Fig. 2.16Gypsum aur Plaster of Paris paani khokar ya lekar ek doosre mein badalte hain.

Do boxes ek loop mein aamne-saamne hain. Left box gypsum, yaani calcium sulphate dihydrate, hai, aur right box Plaster of Paris, yaani hemihydrate, hai. Upar wala arrow, gypsum se Plaster of Paris tak, par heat to 373 K aur loses one and a half water likha hai. Neeche wala arrow, Plaster of Paris se waapas gypsum tak, par add water aur sets hard likha hai.

Doctors Plaster of Paris se casts banate hain jo tooti haddiyon ko sahi position mein rakhte hain. Yeh khilaunon, sajaawati mouldings aur moortiyon, false ceilings, aur painting se pehle deewaron ko chikna karne mein bhi use hota hai. Aajkal tyohaaron ki kai moortiyan isi se banti hain. Jama hua plaster aasaani se nahi ghulta, isliye aisi moortiyon ka visarjan nadiyon aur jheelon ko pradooshit karta hai, aur iski jagah mitti ki moortiyon ko badhaava diya jaata hai. Naam Paris ke aaspaas ke bade gypsum bhandaron se aaya hai, jahan sadiyon tak yeh plaster banaya gaya.

Quick check

3 mein se 1

Washing soda ki ek formula unit mein water of crystallisation ke molecules hote hain.

Answer dekho

Answer 10

Washing soda

N a_{2} C O_{3} \cdot 10 H_{2} O

hai.

Practice · 5 questions

Salts (in-text): answers ke saath

Quick answerEasyNCERT in-text Questions, p. 33, Q1
Tumhari textbook bleaching powder ko $C a (C l O)_{2}$ likhti hai. Iska chemical naam calcium hai.
Answer dekho
Answer hypochlorite
$C a (C l O)_{2}$ calcium hypochlorite hai.
Quick answerEasyNCERT in-text Questions, p. 33, Q2
Bleaching powder banane ke liye chlorine ko kis dry substance ke upar se guzaara jaata hai?
quicklime, $C a O$ limestone, $C a C O_{3}$ slaked lime, $C a (O H)_{2}$ gypsum, $C a S O_{4} \cdot 2 H_{2} O$
Answer dekho
Answer (C) slaked lime, $C a (O H)_{2}$
Dry slaked lime, yaani calcium hydroxide, chlorine ke saath react karke bleaching powder deta hai.
Quick answerEasyNCERT in-text Questions, p. 33, Q3
Ek laundry ka paani sabun ke saath scum banata hai kyunki usmein calcium aur magnesium salts ghule hain. Ise theek karne ke liye laundry ko kaun sa sodium compound daalna chahiye?
baking sodacommon saltcaustic sodawashing soda
Answer dekho
Answer (D) washing soda
Washing soda, $N a_{2} C O_{3} \cdot 10 H_{2} O$ , hardness paida karne wale calcium aur magnesium salts ko insoluble carbonates mein badal deta hai.
Short answerMediumNCERT in-text Questions, p. 33, Q4
Baking soda ko sookhi test tube mein garam kiya jaata hai, aur nikalne wali gas ko lime water mein se bubble karaya jaata hai. Tum kya dekhoge? Test tube mein hone wale change ki equation likho.
Solution dikhao
AnswerLime water doodhiya ho jaata hai, kyunki carbon dioxide nikalti hai.
Garam karne par baking soda toot kar sodium carbonate, paani aur carbon dioxide ban jaata hai. Carbon dioxide lime water ko doodhiya kar deti hai.
$\begin{aligned} 2 N a H C O_{3} \\ \overset{h e a t}{\to} N a_{2} C O_{3} \\ + H_{2} O + C O_{2} \end{aligned}$
Short answerEasyNCERT in-text Questions, p. 33, Q5
Ek moortikaar moorti dhaalne ke liye Plaster of Paris ko paani ke saath milata hai. Jamte samay jo hota hai uski equation likho.
Solution dikhao
AnswerYeh paani leta hai aur phir se gypsum ban jaata hai.
Plaster of Paris paani ke saath milkar gypsum banata hai, jo ek sakht solid hai.
$\begin{aligned} C a S O_{4} \cdot \frac{1}{2} H_{2} O \\ + \frac{3}{2} H_{2} O \\ \overset{}{\to} C a S O_{4} \cdot 2 H_{2} O \end{aligned}$

Recap

Summary aur key points

Litmus, turmeric, methyl orange aur phenolphthalein jaise indicators acids aur bases mein colour badalte hain; olfactory indicators smell badalte hain (Section 2.1.1).
Acids metals ke saath react karke salt aur hydrogen dete hain. Zinc aur aluminium sodium hydroxide ke saath bhi hydrogen dete hain, aur aisa salt banate hain jiske negative ion mein metal aur oxygen hote hain (Section 2.1.2).
Acid ke saath carbonate ya hydrogencarbonate fizz karta hai aur salt, paani aur carbon dioxide banata hai, jo gas lime water ko doodhiya karti hai (Section 2.1.3).
Acid + base → salt + water neutralisation hai. Metal oxides basic hote hain aur non-metal oxides acidic (Section 2.1.4, Section 2.1.6).
Acids aur alkalis paani mein electricity conduct karte hain kyunki woh ions banate hain (Section 2.2).
Acids $H^{+} (a q)$ (yaani $H_{3} O^{+}$ ) ions sirf paani mein banate hain; bases $O H^{-}$ ions dete hain, aur jo bases paani mein ghulte hain woh alkalis hain (Section 2.2.1).
Concentrated acid ya base ko paani mein milane par bahut heat nikalti hai, isliye acid ko hamesha dheere-dheere paani mein daala jaata hai (Activity 2.10).
pH scale (0 se 14) hydrogen-ion concentration naapta hai: 7 neutral hai, 7 se neeche acidic aur 7 se upar basic, aur har unit das guna change hai (Section 2.3).
Strong acids aur bases lagbhag poori tarah ions mein toot jaate hain; weak wale sirf thoda tootte hain (strong and weak acids).
Living things patli pH ranges mein hi kaam karte hain: blood, soil, digestion aur daant, sab pH par depend karte hain (Section 2.3.1).
Salt solution neutral, acidic ya basic hota hai, yeh uske parent acid aur base ki strength par depend karta hai (Section 2.4.2).
Common salt sodium hydroxide, chlorine, hydrogen, bleaching powder, baking soda aur washing soda ka raw material hai (Section 2.4.3).
Kai salt crystals mein har formula unit ke saath ek fixed sankhya mein water molecules hote hain, jo unka water of crystallisation hai, jaise $C u S O_{4} \cdot 5 H_{2} O$ mein; Plaster of Paris paani waapas lekar jamta hai (Section 2.4.4).

Group activity INCERT Group Activity (I) · p. 35

Red-cabbage indicator banao

Tumhe chahiye

red (purple) cabbage ke do-teen patte
garam paani (kisi bade se maango), ek katori aur ek chhanni
paanch chhote glass
nimbu ka ras, vinegar, soda water, baking soda solution aur washing soda solution

Patton ko chhote tukdon mein phaado, unhe garam paani se dhak do aur 15 minute ke liye chhod do.
Purple liquid ko chhaan lo: yahi tumhara indicator hai.
Har test liquid ka thoda sa apne alag glass mein daalo, har ek mein ek chammach indicator milao, aur colours note karo.

Table 2.13Red-cabbage indicator

Liquid	Cabbage indicator ke saath colour	Acidic ya basic?
Nimbu ka ras
Vinegar
Soda water
Baking soda solution
Washing soda solution

Tumhari entries apne aap save hoti hain.

Group activity IINCERT Group Activity (II) · p. 36

Ek soda–acid fire extinguisher banao

Tumhe chahiye

nozzle cap wali ek plastic squeeze bottle
baking soda ka ek strong solution (lagbhag aadha cup)
ek chhoti glass vial aur thoda dhaaga
vinegar
metal tray par ek candle

Baking soda solution ko bottle mein daalo.
Vial ki gardan par dhaaga baandho, use vinegar se bharo aur dhyaan se bottle mein utaaro taaki woh solution ke upar seedhi latki rahe. Dhaage ko cap ke neeche dabaakar cap band karo.
Bahar khuli jagah mein tray par candle jalao. Bottle ko jhukao taaki vinegar solution mein mil jaaye, nozzle ko flame ki taraf karo aur dekho.

Apna NCERT exercise question dhoondo

Hamare practice questions ncert.ai ke liye likhe gaye hain aur NCERT exercises ko follow karte hain. Apni textbook ke question se match karne wala question dhoondo; uska answer uske saath hai.

Tumhari NCERT textbook mein	Yahan practice question
NCERT in-text Question, p. 18	Indicators (in-text) · Q1
NCERT in-text Questions, p. 22, Q1	Acids aur bases ke reactions (in-text) · Q1
NCERT in-text Questions, p. 22, Q2	Acids aur bases ke reactions (in-text) · Q2
NCERT in-text Questions, p. 22, Q3	Acids aur bases ke reactions (in-text) · Q3
NCERT in-text Questions, p. 25, Q1	Paani mein ions (in-text) · Q1
NCERT in-text Questions, p. 25, Q2	Paani mein ions (in-text) · Q2
NCERT in-text Questions, p. 25, Q3	Paani mein ions (in-text) · Q3
NCERT in-text Questions, p. 25, Q4	Paani mein ions (in-text) · Q4
NCERT in-text Questions, p. 25, Q5	Paani mein ions (in-text) · Q5
NCERT in-text Questions, p. 25, Q6	Paani mein ions (in-text) · Q6
NCERT in-text Questions, p. 28, Q1	pH scale (in-text) · Q1
NCERT in-text Questions, p. 28, Q2	pH scale (in-text) · Q2
NCERT in-text Questions, p. 28, Q3	pH scale (in-text) · Q3
NCERT in-text Questions, p. 28, Q4	pH scale (in-text) · Q4
NCERT in-text Questions, p. 33, Q1	Salts (in-text) · Q1
NCERT in-text Questions, p. 33, Q2	Salts (in-text) · Q2
NCERT in-text Questions, p. 33, Q3	Salts (in-text) · Q3
NCERT in-text Questions, p. 33, Q4	Salts (in-text) · Q4
NCERT in-text Questions, p. 33, Q5	Salts (in-text) · Q5
NCERT Exercises Q1	Exercises · Q1
NCERT Exercises Q2	Exercises · Q2
NCERT Exercises Q3	Exercises · Q3
NCERT Exercises Q4	Exercises · Q4
NCERT Exercises Q5	Exercises · Q5
NCERT Exercises Q6	Exercises · Q6
NCERT Exercises Q7	Exercises · Q7
NCERT Exercises Q8	Exercises · Q8
NCERT Exercises Q9	Exercises · Q9
NCERT Exercises Q10	Exercises · Q10
NCERT Exercises Q11	Exercises · Q11
NCERT Exercises Q12	Exercises · Q12
NCERT Exercises Q13	Exercises · Q13
NCERT Exercises Q14	Exercises · Q14
NCERT Exercises Q15	Exercises · Q15

Quick check: MCQs

Shuru karne se pehle1 question
2.1.1 Laboratory mein Acids aur Bases3 questions
2.1.6 Non-metallic Oxide ka Base ke saath Reaction4 questions
2.2.1 Water Solution mein Acid ya Base ka Kya Hota Hai?4 questions
Chemicals se apni raksha4 questions
2.4.2 Salts ka pH2 questions
Washing soda4 questions
Plaster of Paris3 questions

Glossary · 15

Key terms (English + Hindi)

acidअम्लamla: Aisa substance jo paani mein hydrogen ions ( $H^{+}$ ) deta hai. Acids khatte hote hain, blue litmus ko red karte hain aur unka pH 7 se neeche hota hai.Chapter mein pehli baar yahan aaya →
alkaliक्षारkshar: Aisa base jo paani mein ghulkar hydroxide ions deta hai, jaise sodium hydroxide.
antacid: Ek mild base, jaise milk of magnesia, jo pet ke extra acid ko neutralise karne ke liye liya jaata hai.Chapter mein pehli baar yahan aaya →

baseक्षारकksharak: Aisa substance jo acid ke saath react karke salt aur paani deta hai. Bases red litmus ko blue karte hain; jo ghulte hain woh $O H^{-}$ ions dete hain.Chapter mein pehli baar yahan aaya →

chlor-alkali process: Brine (sodium chloride solution) ka electrolysis karke chlorine, hydrogen aur sodium hydroxide banana.Chapter mein pehli baar yahan aaya →

dilutionतनुकरणtanukaran: Acid ya base mein paani milana, jisse uske ions ka concentration kam ho jaata hai.

hydronium ionहाइड्रोनियम आयनhaaidroniyam aayan: $H_{3} O^{+}$ ion: ek water molecule se juda hydrogen ion, yaani paani mein $H^{+}$ ka roop.

indicatorसूचकsoochak: Aisa substance jiska colour (ya smell) acids aur bases mein alag hota hai, jaise litmus, methyl orange ya phenolphthalein.Chapter mein pehli baar yahan aaya →

neutralisationउदासीनीकरणudaaseenikaran: Woh reaction jismein acid aur base ek doosre ko cancel karke salt aur paani banate hain.

olfactory indicatorगंधीय सूचकgandhiya soochak: Aisa substance jiski smell acid ya base mein badal jaati hai, jaise pyaaz, vanilla ya clove oil.Chapter mein pehli baar yahan aaya →

pH scale: Acidity ke liye 0 se 14 tak ka scale: 7 neutral, 7 se neeche acidic, 7 se upar basic. Kam pH matlab zyada hydrogen ions.Chapter mein pehli baar yahan aaya →

saltलवणlavan: Aisa compound jo tab banta hai jab acid ke hydrogen ki jagah metal ya ammonium ion aa jaata hai, jaise neutralisation mein.Chapter mein pehli baar yahan aaya →
strong acidप्रबल अम्लprabal amla: Aisa acid jo paani mein lagbhag poori tarah ions mein toot jaata hai, jaise HCl. Weak acid, jaise acetic acid, sirf thoda tootta hai.Chapter mein pehli baar yahan aaya →

universal indicatorसार्वत्रिक सूचकsaarvatrik soochak: Indicators ka mixture jo har pH par alag colour dikhata hai.Chapter mein pehli baar yahan aaya →

water of crystallisationक्रिस्टलन जलkristalan jal: Salt ke crystals mein salt ke saath ek fixed ratio mein band paani, jaise $C u S O_{4} \cdot 5 H_{2} O$ mein.

Acids, Bases and Salts: Class 10 Science Chapter 2 Hinglish mein

Is chapter mein aap kya seekhenge

2.1 Acids aur Bases ki Chemical Properties ko Samajhna

2.1.1 Laboratory mein Acids aur Bases

Indicators (in-text): answers ke saath

2.1.2 Acids aur Bases Metals ke saath Kaise React Karte Hain?

2.1.3 Metal Carbonates aur Metal Hydrogencarbonates Acids ke saath Kaise React Karte Hain?

2.1.4 Acids aur Bases Ek Doosre ke saath Kaise React Karte Hain?

2.1.5 Metallic Oxides ka Acids ke saath Reaction

2.1.6 Non-metallic Oxide ka Base ke saath Reaction

Acids aur bases ke reactions (in-text): answers ke saath

2.2 Sabhi Acids aur Sabhi Bases mein Common Kya Hai?

2.2.1 Water Solution mein Acid ya Base ka Kya Hota Hai?

Paani mein ions (in-text): answers ke saath

2.3 Acid ya Base Solutions Kitne Strong Hote Hain?

2.3.1 Roz ki Zindagi mein pH ka Mahatva

pH aur living things

Soil ka pH

Hamare digestive system mein pH

pH aur tooth decay

Chemicals se apni raksha

pH scale (in-text): answers ke saath

2.4 Salts ke baare mein aur

2.4.1 Salts ki Family

2.4.2 Salts ka pH

2.4.3 Common Salt se Chemicals

Sodium hydroxide

Bleaching powder

Baking soda

Washing soda

2.4.4 Kya Salts ke Crystals Sach mein Sookhe Hote Hain?

Plaster of Paris

Salts (in-text): answers ke saath

Summary aur key points

Practice questions answers ke saath (NCERT “Exercises”)

Apna NCERT exercise question dhoondo

Quick check: MCQs

Key terms (English + Hindi)

Tum chapter ke end tak pahunch gaye