Important Question Acids Bases and Salt Chapter 2 Science Class 10 CBSE Board

Short Questions Answer

1. What is the common name of sodium hydrogencarbonate?
Answer: Baking soda.

2. What happens when an acid reacts with a metal?
Answer: A salt and hydrogen gas are formed.

3. What is the pH of a neutral solution?
Answer: 7.

4. Name one natural indicator.
Answer: Litmus or turmeric.

5. What type of oxides are metallic oxides?
Answer: Basic oxides.

6. What type of oxides are non-metallic oxides?
Answer: Acidic oxides.

7. What is the chemical formula of Plaster of Paris?
Answer: CaSO₄·½H₂O.

8. Which gas is liberated when an acid reacts with a metal?
Answer: Hydrogen gas.

9. What is the colour of methyl orange in acidic solution?
Answer: Red.

10. What is the chemical formula of washing soda?
Answer: Na₂CO₃·10H₂O.

11. What is the process called when acid is mixed with water?
Answer: Dilution.

12. What is the pH of a strong acid?
Answer: Less than 7.

13. What type of reaction takes place between an acid and a base?
Answer: Neutralisation reaction.

14. What is the main constituent of tooth enamel?
Answer: Calcium hydroxyapatite.

15. Why is acid added to water and not water to acid?
Answer: Because the reaction is exothermic and may cause splashing.

Long Questions Answer

1. Explain how acids and bases react with metals.
Answer: Acids react with metals to form a salt and hydrogen gas.
Example:
Zn+H2​SO4 ​→ ZnSO4​+H2​↑

Bases also react with certain metals to release hydrogen gas.
Example:
2NaOH+Zn → Na2​ZnO2​+H2​↑

2. What is a neutralisation reaction? Give examples.
Answer: A neutralisation reaction is a chemical reaction in which an acid and a base react to form salt and water.
Example:
HCl+NaOH → NaCl+H2​O
H2​SO4​+2KOH → K2​SO4​+2H2​O

3. What happens when acids react with metal carbonates and hydrogencarbonates?
Answer: They form salt, carbon dioxide, and water.
Example:
Na2​CO3​+2HCl → 2NaCl+H2​O+CO2​↑
NaHCO3​+HCl → NaCl+H2​O+CO2​↑

4. Explain the importance of pH in everyday life.
Answer:

• Digestive system: Stomach produces HCl for digestion; antacids neutralise excess acid.
• Tooth decay: Occurs below pH 5.5; toothpaste prevents it.
• Acid rain: Harms aquatic life by lowering pH of water.
• Soil: Proper pH is needed for healthy plant growth.

5. Describe the manufacture and uses of sodium hydroxide.
Answer: Sodium hydroxide is prepared by the chlor-alkali process.

2NaCl+2H2​O → 2NaOH+Cl2​+H2

Uses:

• Making soaps and detergents
• Paper and textile industries
• Production of bleaching powder

6. Write short notes on bleaching powder and its uses.
Answer: Preparation:
Ca(OH)2​+Cl2​ → CaOCl2​+H2​O

Uses:

• For bleaching cotton, linen, and paper
• To disinfect drinking water
• As an oxidising agent

7. What are the differences between strong and weak acids? Give examples.
Answer:

Strong acids: Completely dissociate in water (e.g., HCl, H₂SO₄).

Weak acids: Partially dissociate in water (e.g., CH₃COOH).
Strong acids have low pH values, while weak acids have higher pH values.

8. What is water of crystallisation? Explain with an example.
Answer: Water of crystallisation is the fixed number of water molecules present in one formula unit of a salt.
Example:

CuSO4​⋅5H2​O (Blue copper sulphate)
On heating: CuSO4​⋅5H2​O → CuSO4​+5H2​O

9. What is Plaster of Paris? How is it prepared and used?
Answer: Preparation:

CaSO4​⋅2H2​O373K
​CaSO4​⋅21​H2​O+1.5H2​O

10. What are acids, bases, and salts? Give examples.
Answer:

• Acid: Substance that gives H⁺ ions in water (e.g., HCl).
• Base: Substance that gives OH⁻ ions in water (e.g., NaOH).
• Salt: Formed by neutralisation of acid and base (e.g., NaCl).