D-And F-Block Elements Ques 137

Question: Pure conc. $ HNO_3 $ makes iron passive as the surface is covered with protective layer of

[Orrisa JEE 2002; EAMCET 1993]

Options:

A) $ Fe_2O_3 $

B) FeO

C) $ Fe_3O_4 $

D) $ Fe{{(NO_3)}_3} $

Show Answer

Answer:

Correct Answer: C

Solution:

The passivity of iron is due to the formation of a thin insoluble and invisible iron film on surface which prevents its further reactions. The film is due to the formation of $ Fe_3O_4 $ .



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