D-And F-Block Elements Ques 142

Question: Iron is rendered passive by the action of

[IIT 1982; MP PET 1985; MP PMT 1987; DPMT 1984; KCET 1993]

Options:

A) Conc. $ H_2SO_4 $

B) Conc. $ H_3PO_4 $

C) Conc. $ HCl $

D) Conc. $ HNO_3 $

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Answer:

Correct Answer: D

Solution:

Iron is rendered passive by conc. $ HNO_3 $ and other oxidising agents like $ K_2Cr_2O_7,,KMnO_4 $ , Chloric acid, chromic acid, silver nitrate etc. A specimen of passive iron can be rendered active by scratching the film mechanically or chemically.



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