Chemistry
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.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false but R is true.
Nitric Acid
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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).
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Related Questions
Assertion (A): The yellow colour of nitric acid is removed by using carbon dioxide gas or dry air.
Reason (R): Carbon dioxide gas or dry air drives away NO2 gas from the warm nitric acid.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false but R is true.
Assertion (A): Nitric acid reacts with NaOH/KOH to form salt and water.
Reason (R): Alkalies react with acids to form salt and water.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false but R is true.
Name :
(a) a nitrate of metal which on heating does not give nitrogen dioxide.
(b) a nitrate which on heating leaves no residue behind.
(c) a metal nitrate which on heating is changed into metal oxide.
(d) a metal nitrate which on heating is changed into metal.
(e) a solution which absorbs nitric oxide.
(f) the oxide of nitrogen which turns brown on exposure to air. How is it prepared?
(g) the gas produced when copper reacts with conc. HNO3.
Identify the gas evolved when:
(i) Sulphur is treated with conc. nitric acid.
(ii) A few crystals of KNO3 are heated in a hard glass test tube.