Answers of all 15 questions of chapter 2 NCERT Chemistry. “Get clear and concise answers to 10th-grade NCERT Chapter 2 questions on acids, bases, and salts. Ace your chemistry studies with expert explanations and insights.”

1. A solution turns red litmus blue, its pH is likely to be
(a) 1 (b) 4 (c) 5 (d) 10

Ans: (d) 10 , We know that basic solution turns red litmus blue so pH should be more than 7 , that is 10 here.

2. A solution reacts with crushed egg-shells to give a gas that turns lime-water milky.
The solution contains
(a) NaCl (b) HCl (c) LiCl (d) KCl

Ans: (b) HCl , A gas which turns lime water milky is carbon dioxide, which is release when calcium carbonate (CaCO3) in crushed eggshells reacts with an acid, such as hydrochloric acid (HCl).

3. 10 mL of a solution of NaOH is found to be completely neutralised by 8 mL of a given solution of HCl. If we take 20 mL of the same solution of NaOH, the amount HCl solution (the same solution as before) required to neutralize it will be
(a) 4 mL (b) 8 mL (c) 12 mL (d) 16 mL

Ans: (d) 16ml , NaOH solution gets doubled, so HCl should also get double to neutralise NaOH, 8×2=16ml.

4. Which one of the following types of medicines is used for treating indigestion?
(a) Antibiotic
(b) Analgesic
(c) Antacid
(d) Antiseptic

Ans: (c) Antacid , Antacids are substances that help neutralize excessive stomach acid.

5. Write word equations and then balanced equations for the reaction taking
place when –
(a) dilute sulphuric acid reacts with zinc granules.
(b) dilute hydrochloric acid reacts with magnesium ribbon.
(c) dilute sulphuric acid reacts with aluminium powder.
(d) dilute hydrochloric acid reacts with iron filings.

Ans: (a) dilute sulphuric acid reacts with zinc granules.

Word Equation: Sulphuric acid + Zinc → Zinc Sulphate + Hydrogen gas

Balanced Chemical Equation: H₂SO₄ + Zn → ZnSO₄ + H₂

(b) dilute hydrochloric acid reacts with magnesium ribbon.

Word Equation: Hydrochloric acid + Magnesium → Magnesium chloride + Hydrogen gas

Balanced Chemical Equation: 2HCl + Mg → MgCl₂ + H₂

(c) dilute sulphuric acid reacts with aluminium powder.

Word Equation: Sulphuric acid + Aluminum → Aluminum sulphate + Hydrogen gas

Balanced Chemical Equation: H₂SO₄ + 2Al → Al₂(SO4)₃ + 3H₂

(d) dilute hydrochloric acid reacts with iron filings.

Word Equation: Hydrochloric acid + Iron → Iron chloride + Hydrogen gas

Balanced Chemical Equation: 2HCl + Fe → FeCl₂ + H₂

6. Compounds such as alcohols and glucose also contain hydrogen but are not
categorized as acids. Describe an Activity to prove it.

Ans: You can perform a simple litmus paper test. Acids turn blue litmus paper red, while alcohols and glucose won’t change its color. This experiment demonstrates that even though alcohols and glucose contain hydrogen, they don’t behave as acids.

7. Why does distilled water not conduct electricity, whereas rain water does?

Ans: When rainwater falls from the sky, some gases from the atmosphere gets dissolved in it, such as Nitrogen dioxide(NO₂), Carbon dioxide(CO₂), Sulphur dioxide(SO₂) which forms acid. Now the rainwater is relatively acidic, so it releases H⁺ ions which leads the solution to become the conductor of electricity.

8. Why do acids not show acidic behavior in the absence of water?

Ans: When acid dissolves in water it produce hydronium ions(H₃O⁺), H⁺ + H₂O -> H₃O⁺ this shows the acidic behavior. And this cannot be attained in the absence of water, that is why acid does not show acidic behavior in absence of water.

9. Five solutions A,B,C,D and E when tested with universal indicator showed pH as
4,1,11,7 and 9, respectively. Which solution is
(a) neutral?
(b) strongly alkaline?
(c) strongly acidic?
(d) weakly acidic?
(e) weakly alkaline?
Arrange the pH in increasing order of hydrogen-ion concentration.

Ans: Solutions with pH in Increasing order of hydrogen-ion concentration: B, A, D, E, C. pH Values : B=1 , A = 4, D = 7, E = 9, C=11.

Hence a) Solution D , b) Solution C , c) Solution B, d) Solution A, e) Solution E

10. Equal lengths of magnesium ribbons are taken in test tubes A and B. Hydrochloric
acid (HCl) is added to test tube A, while acetic acid (CH3COOH) is added to test
tube B. Amount and concentration taken for both the acids are same. In which test
tube will the fizzing occur more vigorously and why?

Ans: In tube A fizzing will occur more vigorously because HCl is a strong acid and CH₃COOH is a waek acid. Hence HCl will produce H₂ gas with more speed than CH₃COOH.

11. Fresh milk has a pH of 6. How do you think the pH will change as it turns into
curd? Explain your answer.

Ans: pH of the curd will decrease or it will be less than 6, because curd contains lactic acid hence it is more acidic than milk. So its pH should also be less than that of milk.

12. A milkman adds a very small amount of baking soda to fresh milk.
(a) Why does he shift the pH of the fresh milk from 6 to slightly alkaline?
(b) Why does this milk take a long time to set as curd?

Ans: a) A milkman shift the pH, so that milk does not turn sour easily. Since the baking soda (alkali) does not allow the milk to become acidic easily.

b) As we have added baking soda and it has increased the pH level, so it will take time to became acidic and set as curd.

13. Plaster of Paris should be stored in a moisture-proof container. Explain why?

Ans: Plaster of Paris is stored in a moisture-proof container because it reacts with moisture and forms gypsum which is hard in texture and cannot be used as plaster.

14. What is a neutralisation reaction? Give two examples.

Ans: When an Acid and Base react with each other it forms a salt and water. This process is called Neutralisation Reaction.

The general form of a neutralization reaction can be represented as: Acid + Base → Salt + Water

Examples: a) NaOH + HCl -> NaCl + H₂O b) KOH + H₂SO₄ -> K₂SO₄ + H₂O

15. Give two important uses of washing soda and baking soda.

Ans: Uses of Washing Soda (Sodium Carbonate Na₂CO₃) : In Laundry, In manufacturing of Soap, Glass, Paper.

Uses of Baking Soda (Sodium Hydrogen-carbonate NaHCO₃): As Antacids, Baking Powder in Cakes and Bread.