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ICSE Class 10 Chemistry Question 12 of 63

Study of Compounds — Nitric Acid — Question 20

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Question 20

Assertion (A): Cold and dilute nitric acid oxidise metals to their nitrates and nitric oxide.

Reason (R): Hot and concentrated nitric acid liberates nitrogen dioxide.

  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false but R is true.
Answer

Both A and R are true but R is not the correct explanation of A.

Explanation — Cold and dilute nitric acid oxidises metals to their nitrates and nitric oxide. Hence, the assertion (A) is true.

3Cu + 8HNO3 ⟶ 3Cu(NO3)2 + 4H2O + 2NO

Hot dilute nitric acid or concentrated nitric acid liberates nitrogen dioxide. Hence, the reason (R) is true.

Cu + 4HNO3 ⟶ Cu(NO3)2 + 2H2O + 2NO2

However, reason (R) doesn't explain the action of Cold and dilute nitric acid on metals. So, it is not the correct explanation of assertion (A).