Question

Statement I: Reactivity of aluminium decreases when it is dipped in nitric acid.
Statement II: A protective layer of aluminium nitrate is formed when aluminium is dipped in nitric acid.
(A) I is correct but II is incorrect
(B) I is incorrect but II is correct
(C) Both the statements are correct and II is also the correct explanation of I
(D) Both the statements are correct and II is not the correct explanation of I

Answer 1

Whenever aluminum is dipped in nitric acid, it oxidizes aluminum and a protective layer of $A{l_2}{O_3}$ is formed.
Nitric Acid is a highly corrosive mineral acid. The Pure form of compound is colorless but by time it acquires yellow color due to the decomposition of oxides of nitrogen and water.
Nitric Acid $NH{O_3}$ is used in several ways such as in making dyes, explosives and also when it is, with $HCl$, an aqua regia is formed.

Complete step by step answer:
When aluminum is reacted with nitric acid.
$Al + 6HN{D_3} \to Al{\left( {N{O_3}} \right)_3} + 3N{O_2} + 3{H_2}O$aluminum nitrate, nitrogen dioxide and water is formed.
The dilute nitric acid tends to produce the above products. But Concentrated nitric acid is such a powerful oxidizing agent that it tends to form the Oxide layer on the surface of the metal.
When aluminum is dipped in nitric acid, being a strong oxidizing agent, it oxidizes aluminum and forms a protective layer of$A{l_2}{O_3}$, aluminum oxide on the surface.
One more thing, when aluminum is dipped the reactive of aluminum decreases because of the formation of the oxide layer.
Assertion is Correct but the reason is not correct.

So, the correct answer is Option A .

Note:
When Aluminum is dipped in nitric acid its reactivity decreases as the oxide formation takes place on the surface of metal. Here it is to be noted that nitric acid is a very strong oxidising agent and it oxidises Al readily to its corresponding oxide.