Statement I: Conc. HNO₃ can be transported in aluminium can

Statement II: Al becomes passive after initial reaction

Both Statement I and Statement II are correct and Statement II is the correct explanation of Statement I

The correct answer is option 1. Both Statement I and Statement II are correct, and Statement II is the correct explanation of Statement I.

Let us delve into the chemistry behind the statements and their implications.

Statement I: Concentrated \(HNO_3\) can be transported in an aluminium can

This statement is correct.  When aluminium comes into contact with concentrated nitric acid (\(HNO_3\)), a chemical reaction occurs.

\(Al + 6HNO_3 \rightarrow Al_2O_3 + 6NO_2 + 3H_2O \)

This reaction produces aluminium oxide \((Al_2O_3)\), which forms a thin, protective layer on the surface of the aluminium. This layer is impermeable and adheres strongly to the underlying aluminium, preventing further reaction with the acid. The oxide layer essentially "passivates" the aluminium, meaning it protects the metal from further corrosion or reaction. This allows concentrated nitric acid to be safely transported in aluminium containers, as the protective layer prevents any significant ongoing reaction.

Statement II: Aluminium becomes passive after initial reaction

This statement is also correct and is a well-known phenomenon in chemistry known as passivation:

When aluminium first contacts concentrated nitric acid, it reacts to form aluminium oxide. The aluminium oxide layer \((Al_2O_3)\) is very stable and adheres well to the aluminium surface. This layer prevents further exposure of the underlying aluminium to the nitric acid. As a result of this oxide layer, the aluminium becomes "passive." In this passive state, the aluminium is protected from further chemical reactions, including further attack by the nitric acid.

Relationship Between the Statements:

Statement II explains why Statement I is true. The passivation process described in Statement II (formation of a protective aluminium oxide layer) is the reason why aluminium can safely hold concentrated nitric acid. Without this passivation, the aluminium would continue to react with the nitric acid, potentially leading to container failure.