Single Choice

Fe is made passive by:

A$$dil.H_2SO_4$$
B$$dil.HCl$$
Correct Answer
C$$aqua-regia$$
D$$conc.H_2SO_4$$

Solution

Aqua regia and cold conc. nitric acid makes iron passive. The passivity of the iron is due to the deposit of a thin layer of iron oxide on the surface.

SIMILAR QUESTIONS

d - block and f - block Elements

Which of the following is an amphoteric oxide?

d - block and f - block Elements

Which of the following compound is blue?

d - block and f - block Elements

Which of the following oxides are basic in nature ?

d - block and f - block Elements

Zinc oxide is normally white but turns yellow on heating and becomes white again on cooling because of:

d - block and f - block Elements

The Oxidation states of $$Cr$$ in $$[Cr(H_2O)_6]Cl_3, [Cr(C_6H_6)_2]$$, and $$K_2[Cr(CN)_2(O)_2(O_2)(NH_3]$$ respectively are:

d - block and f - block Elements

Which of the following compounds is metallic and ferromagnetic?

d - block and f - block Elements

In acidic medium, $$H_2O_2$$ changes $$Cr_2O_7^{- 2}$$ to $$CrO_5$$ which has two ($$-O- O-$$) bonds oxidation state of $$Cr$$ in $$CrO_5$$ is:

d - block and f - block Elements

Name the oxometal anions of the first series of the transition metals in which the metal exhibits the oxidation state equal to its group number.

d - block and f - block Elements

$$Cr - C$$ bond in the compound $$[Cr(CO)_6]$$ shows $$\pi$$ - character due to :

d - block and f - block Elements

Passivity of iron is due to formation of:

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