Question

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Answer 1

12.answer:When an iron nail immersed in the solution of copper sulphate than iron displaces copper from the solution of copper sulphate because iron is more reactive than copper. Therefore copper sulphate solution colour changes from blue to pale green.

Reaction

CuSO4 (aq) + Fe (s) → FeSO4 (aq) + Cu (s)

In this reaction following two processes take place:

Cu²⁺ + 2e = Cu⁰ (re­duc­tion process, Cu²⁺ is the ox­i­dizing agent)

Fe⁰ – 2e = Fe²⁺ (ox­i­da­tion process, Fe⁰ is the re­duc­ing agent)

The reaction can be double displacement reaction as well as redox reaction (oxidation and reduction both takes place simultaneously).

Explanation:

When an iron nail is dipped in copper sulphate solution, a brown coating of copper is formed in the surface of iron and the colour of copper sulphate solution changes from blue to pale green. The reaction shows that iron is more reactive than copper because it displaces copper from the copper sulphate solution. The iron passes into the solution as Fe (II) forming the ferrous sulphate solution.

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Answer 2

Explanation:

13. Acid plays a vital role in the process of digestion, whatever we intake it goes directly into our stomach. And hydrochloric acid present in our stomach helps to digest the food and helps in metabolism of essential nutrients.

14. Aerobic respiration- The respiration which takes place with the presence of oxygen is known as aerobic respiration. Eg- Plants and human beings.

Anaerobic respiration- The respiration which takes place with the absence of oxygen is known as anaerobic respiration.Eg- Respiration in unicellular organism.

15. In this figure, the properties of magnet is shown.

There are two poles i.e North pole and south pole.

i) Like charges repel each other.

ii) Unlike charges attract each other.

16. Ozone layer plays a vital role and it is like a blanket that spreads and provide protection for human beings by capturing harmful ultraviolet rays from sun. Damage to ozone layer is a great concern for us because the harmful rays can easily enter our atmosphere and can cause skin cancer, allergies and rashes.

There are several measures to protect ozone layer they are:

i) By minimising the use of ac and refrigerator.

ii) By not burning the plastics and harmful waste.