10th Metals and Non Metals NCERT Solution

Answers to Science Questions

1. Which of the following pairs will give displacement reactions?

(a) NaCl solution and copper metal

(b) MgCl₂ solution and aluminium metal

(c) FeSO₄ solution and silver metal

(d) AgNO₃ solution and copper metal

Answer: (d) AgNO₃ solution and copper metal

2. Which of the following methods is suitable for preventing an iron frying pan from rusting?

(a) Applying grease

(b) Applying paint

(c) Applying a coating of zinc

(d) All of the above.

Answer: (d) All of the above.

3. An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be

(a) calcium

(b) carbon

(c) silicon

(d) iron

Answer: (a) calcium

4. Food cans are coated with tin and not with zinc because

(a) zinc is costlier than tin.

(b) zinc has a higher melting point than tin.

(c) zinc is more reactive than tin.

(d) zinc is less reactive than tin.

Answer: (c) zinc is more reactive than tin.

5. You are given a hammer, a battery, a bulb, wires and a switch.

(a) How could you use them to distinguish between samples of metals and non-metals?

Answer: (a) Use the hammer to hit the samples. Metals will be malleable and change shape, while non-metals will break or crumble. Use the battery, bulb, wires, and switch to make a circuit. Metals will conduct electricity and light the bulb, while non-metals will not.

(b) Assess the usefulness of these tests in distinguishing between metals and non-metals.

Answer: (b) These tests are useful because malleability and electrical conductivity are key properties that differentiate metals from non-metals.

6. What are amphoteric oxides? Give two examples of amphoteric oxides.

Answer: Amphoteric oxides are oxides that can react with both acids and bases. Examples are aluminium oxide (Al₂O₃) and zinc oxide (ZnO).

7. Name two metals which will displace hydrogen from dilute acids, and two metals which will not.

Answer: Metals that will displace hydrogen: Zinc (Zn) and Iron (Fe). Metals that will not displace hydrogen: Copper (Cu) and Silver (Ag).

8. In the electrolytic refining of a metal M, what would you take as the anode, the cathode and the electrolyte?

Answer: Anode: Impure metal M; Cathode: Pure metal M; Electrolyte: A solution of a salt of metal M.

9. Pratyush took sulphur powder on a spatula and heated it. He collected the gas evolved by inverting a test tube over it, as shown in figure below.

(a) What will be the action of gas on

(i) dry litmus paper?

Answer: (a) (i) Dry litmus paper: No action.

(ii) moist litmus paper?

Answer: (a) (ii) Moist litmus paper: Turns blue litmus paper red.

(b) Write a balanced chemical equation for the reaction taking place.

Answer: (b) S + O₂ → SO₂

10. State two ways to prevent the rusting of iron.

Answer: 1. Applying a coating of paint. 2. Applying a coating of zinc (galvanization).

11. What type of oxides are formed when non-metals combine with oxygen?

Answer: Non-metals combine with oxygen to form acidic oxides.

12. Give reasons.

(a) Platinum, gold and silver are used to make jewellery.

Answer: (a) Platinum, gold, and silver are used to make jewellery because they are resistant to corrosion and do not tarnish.

(b) Sodium, potassium and lithium are stored under oil.

Answer: (b) Sodium, potassium, and lithium are stored under oil because they are highly reactive with air and water.

(c) Aluminium is a highly reactive metal, yet it is used to make utensils for cooking.

Answer: (c) Aluminium is used for utensils because it forms a protective oxide layer that prevents further reaction.

(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction.

Answer: (d) Carbonate and sulphide ores are converted into oxides because it is easier to extract metals from oxides.

13. You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels.

Answer: Lemon or tamarind juice contains acids that react with the tarnish (copper oxide) on the vessels, dissolving it and revealing the shiny copper underneath.

14. Differentiate between metal and non-metal on the basis of their chemical properties.

Answer: Metals form basic oxides and lose electrons to form positive ions. Non-metals form acidic oxides and gain electrons to form negative ions.

15. A man went door to door posing as a goldsmith. He promised to bring back the glitter of old and dull gold ornaments. An unsuspecting lady gave a set of gold bangles to him which he dipped in a particular solution. The bangles sparkled like new but their weight was reduced drastically. The lady was upset but after a futile argument the man beat a hasty retreat. Can you play the detective and find out the nature of the solution he had used?

Answer: The man likely used a solution containing a strong acid, such as nitric acid, which dissolved some of the gold, reducing the weight while making the bangles appear shiny.

16. Give reasons why copper is used to make hot water tanks and not steel (an alloy of iron).

Answer: Copper is used because it is resistant to corrosion by hot water, while steel can rust when exposed to water and air.