Concept:Aluminium becomes passive because a protective oxide layer on its surface blocks further reaction with the acid.
Explanation:Trioxonitrate (V) acid,
HNO3, is a powerful oxidising agent.
When aluminium is placed in either dilute or concentrated
HNO3, the acid rapidly oxidises the surface of the metal.
This produces an insoluble layer of aluminium oxide,
Al2O3, on the metal.
The oxide layer is firmly attached and prevents the acid from making further contact with the aluminium underneath.
This condition is called passivity.
As a result, the expected metal-acid reaction does not continue.
Hence, aluminium does not react visibly with dilute or concentrated trioxonitrate (V) acid.
Answer:D. An insoluble oxide is formed on its surface which renders it passive.