Question

Why does reactivity of al decrease when dipped in hno3?

Answer 1

Hey Friend,

Aluminum has a great affinity towards oxygen. And HNO3 is a good oxidizing agent! When Al is dipped in HNO3, a protective covering of insoluble Al2O3 is formed. This prevents the further oxidation of the aluminum and makes the metal non-reactive!

The reaction is...
Al + HNO3 ---> Al2O3 + NO2 + H2O

Hope it helps!

Answer 2

Answer:

The reactivity of Aluminum decreases when dipped in nitric acid because Aluminum (Al) has great affinity toward oxygen while nitric acid (HNO₃) is a strong oxidizing agent. So when aluminum reacts with nitric acid, it forms a layer of Aluminum oxide (Al₂O₃) on its surface which is non-reactive and hence prevents further reaction of aluminum with the acid. The following reaction takes place:

Al + HNO₃ = Al₂O₃ + NO₂ + H₂O

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