General Science Question Answers Chapter 12 Introduction to Acid and Base Class 8 Maharashtra Board

Question Answers For All Chapters – General Science Class 8

Exercise

1. Identify the following solutions as Acid or Base

2. Write the chemical names of the given formulae

3. Why is Sulphuric Acid important in the chemical industry?

• Sulphuric acid (H₂SO₄) is called the “King of Chemicals” because it is widely used in various industries.

Uses of Sulphuric Acid in Industry:

1. Fertilizer Industry – Used to make chemical fertilizers like ammonium sulfate and superphosphate.
2. Battery Manufacturing – Used in car batteries and power storage batteries.
3. Petroleum Industry – Helps in refining crude oil and removing impurities.
4. Metal Processing – Used in cleaning metals before painting or coating.
5. Chemical Production – Used to manufacture detergents, paints, plastics, and medicines.
6. Textile Industry – Helps in making synthetic fibers like rayon.

4. Give Answers

(a) Which acid is used for getting chloride salt?

• Hydrochloric acid (HCl) is used to make chloride salts like sodium chloride (NaCl).

(b) By squeezing lemon on a piece of rock, the gas liberated turned lime water milky. Which compound is present in the rock?

• The rock contains calcium carbonate (CaCO₃).
• When lemon juice (which contains citric acid) reacts with calcium carbonate, carbon dioxide (CO₂) gas is released, which turns lime water milky.

(c) The label on the bottle of chemical is spoiled. How will you find whether the chemical is acidic or not?

Use a litmus test:

• If blue litmus turns red, the chemical is an acid.

Use a methyl orange test:

• If methyl orange turns red, it confirms the chemical is an acid.

Use a pH test:

• If the pH is below 7, the substance is an acid.

5. Answer the following questions

(a) Difference between Acid and Base

(b) Why indicator does not get affected by salt?

• Indicators change color only in acids or bases.
• Salt is neutral, so it does not react with indicators like litmus, phenolphthalein, or methyl orange.

(c) Which substances are produced by neutralization process ?

• In a neutralization reaction, an acid and a base react to form salt and water.
  • Example: HCl + NaOH → NaCl + H₂O

(d) Which are the industrial uses of acids?

• Sulphuric Acid (H₂SO₄) – Used in making fertilizers, paints, and batteries.
• Hydrochloric Acid (HCl) – Used in cleaning metal surfaces and making salts.
• Nitric Acid (HNO₃) – Used in explosives and fertilizers.
• Acetic Acid (CH₃COOH) – Used in food (vinegar) and medicines.

6. Select proper word given in bracket and fill in the blanks.

(a) The main constituent of an acid is H⁺ ions.

(b) The main constituent of a base is OH⁻ ions.

(c) Tartaric acid is a natural acid.

7. Match the Pairs

8. State whether the following statements are True or False

(a) Oxides of metals are acidic in nature. → False (Metal oxides are basic).

(b) Table salt is acidic. → False (Table salt is neutral).

(c) Metals corrode due to salts. → True.

(d) Salts are neutral. → True.

9. Classify the following substances into Acidic, Basic, or Neutral