Class 10 Science · Chapter 2
Short answer: NCERT Class 10 Science Chapter 2 Acids, Bases and Salts me 18 in-text aur 15 exercise questions hain. Chapter me acid-base ki properties, indicators, pH scale, neutralisation, aur 5 important salts (washing soda, baking soda, bleaching powder, Plaster of Paris, common salt) padhaye jaate hain. Har question ka step-by-step solution neeche diya gaya hai.
Chapter 2, Chapter 1 ka seedha extension hai. pH scale aur salts ka part har saal aata hai — yahi sabse scoring hissa hai.
Chapter 2 Summary — 5 Minute Revision
Acid, Base aur Salt
- Acid — paani me ghulne par H+ (hydronium, H3O+) ion deta hai. Swad khatta, blue litmus ko laal karta hai.
- Base — paani me ghulne par OH− ion deta hai. Swad kadva, chhune me sabun jaisa, red litmus ko neela karta hai.
- Salt — acid aur base ke neutralisation se banta hai.
Indicators
| Indicator | Acid me | Base me |
|---|---|---|
| Litmus | Laal | Neela |
| Methyl orange | Laal | Peela |
| Phenolphthalein | Colourless | Gulabi |
| Olfactory (pyaaz, vanilla) | Smell rehti hai | Smell chali jaati hai |
↔ Table ko side me swipe karein
Acid ke 4 important reactions
- Metal ke saath → Salt + H2 gas (pop test se pehchaan)
- Metal carbonate / hydrogencarbonate ke saath → Salt + H2O + CO2 (lime water doodhiya)
- Base ke saath → Salt + Water (neutralisation)
- Metal oxide ke saath → Salt + Water (metal oxide basic hote hain)
pH scale
0 se 14 tak. 7 = neutral, 7 se kam = acidic, 7 se zyada = basic. pH jitna kam, H+ ki concentration utni zyada.
- Hamara sharir pH 7.0–7.8 ke beech kaam karta hai.
- Acid rain ka pH 5.6 se kam hota hai.
- Daanton ka enamel pH 5.5 se neeche kharab hone lagta hai.
5 important salts
| Salt | Formula | Kaam |
|---|---|---|
| Common salt | NaCl | Khana, NaOH/washing soda/baking soda ka raw material |
| Bleaching powder | CaOCl2 | Kapde bleach, paani disinfect |
| Baking soda | NaHCO3 | Antacid, baking powder, agni-shamak |
| Washing soda | Na2CO3·10H2O | Hard water softening, glass & soap industry |
| Plaster of Paris | CaSO4·½H2O | Plaster (fracture), decoration, moulds |
↔ Table ko side me swipe karein
In-Text Questions — Solutions
Q1. Sirf red litmus paper se distilled water, acid aur base kaise pehchaanenge?
Red litmus paper sirf base ke saath neela hota hai. Isliye:
- Teeno test tubes me red litmus paper daaliye. Jisme wo neela ho gaya — wahi base hai.
- Ab isi neele ho chuke litmus paper ko bache do test tubes me daaliye. Jisme wo dobara laal ho gaya — wahi acid hai.
- Jisme koi change nahi hua — wahi distilled water hai.
Q2. Curd aur khatti cheezein brass/copper ke bartan me kyun nahi rakhni chahiye?
Curd aur khatte padarth me acid hota hai. Ye acid brass aur copper ke saath react karke zehreele (toxic) copper salts bana deta hai, jo khane ko kharab aur sehat ke liye haanikarak bana dete hain.
Q3. Acid + metal se kaunsi gas nikalti hai? Test kaise karein?
Hydrogen gas (H2) nikalti hai.
Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)
Test (pop test): gas ke paas jalti hui candle ya matchstick le jaane par 'pop' ki awaaz ke saath wo jal jaati hai. Yahi hydrogen ki pehchaan hai.
Q4. Metal compound A + dilute HCl → effervescence, gas candle bujha deti hai. Equation likhiye.
Gas jo candle bujha de = CO2. Aur ek product calcium chloride hai, isliye compound A = calcium carbonate (CaCO3).
CaCO3(s) + 2HCl(aq) → CaCl2(aq) + H2O(l) + CO2(g)
Q5. HCl, HNO3 acidic hain par alcohol aur glucose kyun nahi?
Acidic hone ke liye padarth ko paani me ghulkar H+ (H3O+) ions dene padte hain.
HCl aur HNO3 paani me ionise hokar H+ dete hain:
HCl + H2O → H3O+ + Cl−
Alcohol aur glucose me hydrogen to hota hai, par wo paani me ionise nahi hote — H+ ion release nahi karte. Isliye ve acidic nahi hain.
Q6. Acid ka aqueous solution bijli kyun conduct karta hai?
Paani me acid ionise hokar free moving ions — H3O+ aur anions — deta hai. Ye charged ions hi current carry karte hain, isliye solution bijli conduct karta hai.
Q7. Sookhi HCl gas sookhe litmus paper ka rang kyun nahi badalti?
Sookhi HCl gas me paani nahi hota, isliye wo ionise nahi ho pati aur H+ ions produce nahi karti. Acidic behaviour dikhane ke liye H+ ions zaroori hain — isliye sookha litmus paper rang nahi badalta. Geela litmus paper turant laal ho jayega.
Q8. Acid ko paani me milate waqt acid ko paani me daalte hain, ulta kyun nahi?
Acid ka paani me ghulna bahut zyada exothermic hai. Agar acid me paani daala jaye to itni heat ek jagah nikalti hai ki mixture chhalak kar ya bartan toot kar jal sakta hai.
Acid ko dheere-dheere paani me daalne par heat poore paani me fail jaati hai aur mixture surakshit rehta hai. Hamesha: Acid → Water.
Q9. Acid dilute karne par H3O+ ki concentration par kya asar padta hai?
Paani badhne se same H3O+ ions zyada volume me fail jaate hain, isliye unki concentration ghat jaati hai aur solution ka pH badh jata hai (kam acidic ho jata hai).
Q10. NaOH solution me aur base ghol dein to OH− ka kya hoga?
Zyada base ghulne se aur zyada OH− ions bante hain, isliye OH− ki concentration badh jaati hai aur solution zyada basic (pH zyada) ho jata hai.
Q11. Solution A ka pH 6, B ka pH 8 — kis me H+ zyada? Kaun acidic, kaun basic?
Solution A (pH 6) me hydrogen ion ki concentration zyada hai — pH jitna kam, H+ utna zyada.
A acidic hai (pH < 7) aur B basic hai (pH > 7).
Q12. H+(aq) ki concentration ka solution ki prakriti par kya asar?
H+ jitna zyada, solution utna zyada acidic (pH kam). H+ jitna kam, solution utna zyada basic (pH zyada).
Q13. Kya basic solutions me bhi H+ ions hote hain?
Haan. Paani khud thoda sa ionise hota hai, isliye har aqueous solution me H+ aur OH− dono hote hain.
Basic solution isliye basic hai kyunki usme OH− ki concentration H+ se zyada hoti hai — na ki isliye ki H+ bilkul nahi hai.
Q14. Kisan mitti me quick lime / slaked lime / chalk kab daalta hai?
Jab mitti zyada acidic ho jaye (pH kam ho). Ye teeno padarth basic hain, isliye ye mitti ke acid ko neutralise karke pH ko fasal ke layak (lagbhag neutral) bana dete hain.
Q15. CaOCl2 ka common naam kya hai?
Bleaching powder (calcium oxychloride).
Q16. Chlorine se treat karne par bleaching powder kaunsa padarth deta hai?
Slaked lime — calcium hydroxide, Ca(OH)2.
Ca(OH)2 + Cl2 → CaOCl2 + H2O
Q17. Hard water softening ke liye kaunsa sodium compound use hota hai?
Washing soda — sodium carbonate, Na2CO3·10H2O.
Q18. Sodium hydrogencarbonate ko garam karne par kya hoga? Aur Plaster of Paris + water?
(a) Baking soda garam karne par toot kar sodium carbonate, paani aur carbon dioxide deta hai:
2NaHCO3 Δ→ Na2CO3 + H2O + CO2
(b) Plaster of Paris paani milane par jamkar (set hokar) gypsum ban jata hai:
CaSO4·½H2O + 1½H2O → CaSO4·2H2O
Poore Class 10 Science ke handwritten colour notes
IITian & district toppers ke banaye short notes — revision-ready, diagram ke saath. Board se pehle poora syllabus 3 din me revise.
Exercise Questions — Solutions (Q1–Q15)
Q1. Jo solution red litmus ko neela kar de, uska pH kya hoga?
Answer: (d) 10
Red litmus ko neela sirf base karta hai, aur base ka pH 7 se zyada hota hai. Diye gaye options me sirf 10 hi 7 se zyada hai.
Q2. Jo solution ande ke chhilke se gas de jo lime water ko doodhiya kar de, usme kya hai?
Answer: (b) HCl
Ande ka chhilka calcium carbonate ka hota hai. Acid ke saath ye CO2 deta hai, jo lime water ko doodhiya karta hai. Diye gaye options me sirf HCl acid hai.
CaCO3 + 2HCl → CaCl2 + H2O + CO2
Q3. 10 mL NaOH ko 8 mL HCl neutralise karta hai. 20 mL NaOH ke liye kitna HCl chahiye?
Answer: (d) 16 mL
Neutralisation me matra ka anupaat sthir rehta hai. NaOH dugna (10 → 20 mL) hua, isliye HCl bhi dugna chahiye: 8 × 2 = 16 mL.
Q4. Indigestion (badhazmi) ke liye kaunsi dawa use hoti hai?
Answer: (c) Antacid
Pet me zyada HCl banne se badhazmi hoti hai. Antacid (jaise milk of magnesia, Mg(OH)2) ek halka base hai jo is acid ko neutralise kar deta hai.
Q5. Word equation aur balanced equation likhiye
(a) Dilute sulphuric acid + zinc granules → Zinc sulphate + Hydrogen
Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2(g)
(b) Dilute hydrochloric acid + magnesium ribbon → Magnesium chloride + Hydrogen
Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
(c) Dilute sulphuric acid + aluminium powder → Aluminium sulphate + Hydrogen
2Al(s) + 3H2SO4(aq) → Al2(SO4)3(aq) + 3H2(g)
(d) Dilute hydrochloric acid + iron filings → Ferrous chloride + Hydrogen
Fe(s) + 2HCl(aq) → FeCl2(aq) + H2(g)
Q6. Alcohol aur glucose me hydrogen hai par acid nahi — activity se sabit kijiye
Activity: ek beaker me alcohol (ya glucose) ka solution lijiye. Usme do keel (nails) daal kar unhe rubber cork me fix kijiye. Keelon ko battery, bulb aur switch se jod kar circuit poora kijiye.
Observation: bulb nahi jalega.
Conclusion: bulb na jalna dikhata hai ki solution me free ions nahi hain, yaani alcohol/glucose paani me ionise hokar H+ nahi dete. Yahi activity HCl ke saath karein to bulb jal jayega. Isliye alcohol aur glucose acid nahi hain.
Q7. Distilled water bijli conduct nahi karta par baarish ka paani karta hai — kyun?
Distilled water bilkul shuddh hota hai — usme koi ghula hua salt ya acid nahi hota, isliye free ions nahi hote aur wo conduct nahi karta.
Baarish ka paani hawa se CO2 aur dusri gases ghol leta hai, jisse halka carbonic acid ban jata hai. Ye ionise hokar ions deta hai, isliye baarish ka paani bijli conduct karta hai.
Q8. Paani ke bina acid apna acidic vyavhaar kyun nahi dikhate?
Acidic vyavhaar ke liye H+ (H3O+) ions zaroori hain. Acid ye ions tabhi deta hai jab wo paani me ionise ho. Paani ke bina ionisation nahi hoti, H+ nahi bante — isliye acidic vyavhaar nahi dikhta.
Q9. Paanch solutions ka pH 4, 1, 11, 7, 9 — pehchaaniye
(a) Neutral — D (pH 7)
(b) Strongly alkaline — C (pH 11)
(c) Strongly acidic — B (pH 1)
(d) Weakly acidic — A (pH 4)
(e) Weakly alkaline — E (pH 9)
Hydrogen-ion concentration ke badhte kram me pH: 11 < 9 < 7 < 4 < 1
(pH jitna kam, H+ utna zyada — isliye pH ghatte kram me likha jata hai.)
Q10. Magnesium ribbon par HCl aur acetic acid — kis me fizzing zyada hogi?
Test tube A (HCl) me fizzing zyada vigorous hogi.
HCl ek strong acid hai — paani me poori tarah ionise hokar bahut zyada H+ ions deta hai. Acetic acid weak acid hai, sirf thoda sa ionise hota hai.
Zyada H+ matlab magnesium ke saath tez reaction aur zyada hydrogen gas — isliye A me fizzing zyada.
Q11. Taaza doodh ka pH 6 hai — curd banne par pH ka kya hoga?
Curd banne par pH 6 se kam ho jayega.
Kyunki doodh ke lactose se bacteria lactic acid banate hain. Acid badhne se H+ ki concentration badhti hai aur pH gir jata hai — isliye curd doodh se zyada khatta hota hai.
Q12. Doodhwala doodh me thoda baking soda kyun milata hai?
(a) Baking soda halka base hai. Ise milane se doodh ka pH 6 se badhkar halka alkaline ho jata hai. Alkaline doodh jaldi khatta nahi hota, isliye wo zyada der tak taaza rehta hai.
(b) Curd jamne ke liye doodh ko acidic hona padta hai. Ab pehle bacteria ko us extra base ko neutralise karna padega, uske baad hi acid banna shuru hoga — isliye ye doodh curd banne me zyada samay leta hai.
Q13. Plaster of Paris ko moisture-proof container me kyun rakhte hain?
Namee (moisture) ke sampark me aate hi Plaster of Paris paani se react karke gypsum ban jata hai aur sakht (hard) ho jata hai:
CaSO4·½H2O + 1½H2O → CaSO4·2H2O
Ek baar gypsum ban gaya to wo dobara plaster ki tarah use nahi ho sakta. Isliye ise hamesha sookhe, moisture-proof container me rakha jata hai.
Q14. Neutralisation reaction kya hai? Do udaharan dijiye
Jab ek acid aur ek base aapas me react karke salt aur paani banate hain, use neutralisation reaction kehte hain.
Acid + Base → Salt + Water
Example 1:
NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)
Example 2:
Ca(OH)2(aq) + H2SO4(aq) → CaSO4(aq) + 2H2O(l)
Q15. Washing soda aur baking soda ke do-do upyog
Washing soda (Na2CO3·10H2O):
- Hard water ko soft karne me (permanent hardness hatana)
- Glass, soap aur paper industry me
Baking soda (NaHCO3):
- Antacid ke roop me — pet ke zyada acid ko neutralise karne me
- Baking powder me, jisse cake aur bread phoolte hain (CO2 nikalta hai)
Important Equations — Ek Nazar Me
| Reaction / Concept | Equation | Yaad rakhein |
|---|---|---|
| Acid + Metal | Zn + 2HCl → ZnCl2 + H2↑ | Pop test |
| Acid + Carbonate | CaCO3 + 2HCl → CaCl2 + H2O + CO2↑ | Lime water doodhiya |
| Acid + Base | NaOH + HCl → NaCl + H2O | Neutralisation |
| Acid + Metal oxide | CuO + 2HCl → CuCl2 + H2O | Metal oxide basic hote hain |
| Chlor-alkali | 2NaCl + 2H2O → 2NaOH + Cl2 + H2 | Cl2 anode par, H2 cathode par |
| Bleaching powder | Ca(OH)2 + Cl2 → CaOCl2 + H2O | CaOCl2 |
| Baking soda banana | NaCl + H2O + CO2 + NH3 → NH4Cl + NaHCO3 | Solvay process |
| Baking soda heating | 2NaHCO3 Δ→ Na2CO3 + H2O + CO2 | Cake phoolna |
| Washing soda | Na2CO3 + 10H2O → Na2CO3·10H2O | Hydrated salt |
| Plaster of Paris | CaSO4·½H2O + 1½H2O → CaSO4·2H2O | Gypsum ban jata hai |
| Gypsum se PoP | CaSO4·2H2O 373K→ CaSO4·½H2O + 1½H2O | 373 K se zyada mat karein |
↔ Table ko side me swipe karein
Common Mistakes — Yahan Marks Kat te Hain
- Plaster of Paris ka formula galat likhna. Sahi hai CaSO4·½H2O — aadha (½) paani, ek nahi. Ye 1-mark ka fixed question hai.
- pH aur H+ ka ulta samajhna. pH kam = H+ zyada. Q9 me yahi galti sabse zyada hoti hai.
- "Basic solution me H+ hota hi nahi" likh dena. Hota hai — bas OH− usse zyada hota hai.
- Acid ko paani me daalna vs paani ko acid me. Hamesha acid → water. Ulta likha to poora mark chala jata hai.
- Washing soda ka formula bina 10H2O ke likhna. Sahi: Na2CO3·10H2O.
- Gas ka test bhool jana. H2 = pop sound, CO2 = lime water doodhiya. Question me test poocha jata hai, sirf gas ka naam nahi.
Board-Style Important Questions
- 1 mark: Plaster of Paris ka rasayanik sutra likhiye aur ise moisture se door kyun rakhte hain?
- 2 marks: Bleaching powder kaise banaya jata hai? Balanced equation ke saath do upyog likhiye.
- 3 marks: pH scale kya hai? Daanton ka decay pH se kaise juda hai, aur toothpaste basic kyun hota hai?
- 3 marks: Chlor-alkali process ka naam kyun pada? Teeno products aur unka ek-ek upyog likhiye.
- 5 marks: (i) Baking soda banane ki equation aur do upyog. (ii) Ise garam karne par kya hota hai? (iii) Washing soda se kaise sambandhit hai?
Quick Quiz — Score Check Karein
Q1. Acid paani me ghulne par kaunsa ion deta hai?
Q2. Phenolphthalein indicator base me kaunsa rang dikhata hai?
Q3. Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g) reaction me nikalti hui gas ka pop test kaise hota hai?
Q4. CaCO3(s) + 2HCl(aq) → CaCl2(aq) + H2O(l) + CO2(g) — is reaction me banti hui gas lime water ka kya karti hai?
Q5. Alcohol aur glucose me hydrogen hone ke bawajood ye acidic kyun nahi hain?
Q6. Sookhi HCl gas sookhe litmus paper ka rang kyun nahi badalti?
Q7. Acid ko paani me milate waqt hamesha kya karna chahiye?
Q8. Solution A ka pH 6 hai aur Solution B ka pH 8. Kis solution me H+ ion concentration zyada hai?
Q9. Baking soda (NaHCO3) ka mukhya upyog kya hai jo chapter me diya gaya hai?
Q10. Plaster of Paris ka chemical formula kya hai?
Aksar Poochhe Jaane Wale Sawaal
Class 10 Science Chapter 2 me kitne questions hain?
Is chapter me 18 in-text questions aur 15 exercise questions hain — total 33 questions, jinke solutions upar diye gaye hain.
pH scale kya hai aur iski range kitni hoti hai?
pH scale 0 se 14 tak hoti hai. pH 7 neutral hai, 7 se kam acidic aur 7 se zyada basic. pH jitna kam hoga, hydrogen ion (H+) ki concentration utni zyada hogi.
Plaster of Paris ka formula kya hai?
Plaster of Paris ka formula CaSO4·½H2O hai — calcium sulphate hemihydrate. Ye gypsum (CaSO4·2H2O) ko 373 K par garam karke banaya jata hai.
Baking soda aur washing soda me kya farak hai?
Baking soda sodium hydrogencarbonate (NaHCO3) hai, jo antacid aur baking powder me use hota hai. Washing soda sodium carbonate decahydrate (Na2CO3·10H2O) hai, jo hard water softening aur glass-soap industry me use hota hai. Baking soda ko garam karne par washing soda ka raw material Na2CO3 banta hai.
Acid ko paani me milate waqt kya savdhani rakhni chahiye?
Hamesha acid ko dheere-dheere paani me daalein, paani ko acid me kabhi nahi. Ye reaction bahut exothermic hai — ulta karne par mixture chhalak sakta hai ya bartan toot sakta hai.
Chapter 2 board exam ke liye kitna important hai?
CBSE chapter-wise weightage officially publish nahi karta. Practically pH scale aur paanch important salts (washing soda, baking soda, bleaching powder, Plaster of Paris, common salt) sabse zyada poochhe jaate hain — inhe zaroor cover karein.
Class 10 Science — Saare Chapters
Board exam tak sirf revision karna hai?
Class 10 Science ke saare chapters ke colour handwritten short notes — diagrams, formulas aur important points ek jagah.
NCERT Kaksha ek swatantra shaikshik platform hai aur NCERT ya CBSE se aadhikarik roop se sambaddh (officially affiliated) nahi hai. Kisi galti ki jaankari dene ke liye contact kijiye.