Question

Iron is rendered passive by treatment with concentrated

• A. $H_{2}S{O}_4$
• B. $H_{3}P{O}_4$
• C. HCl
• D. $HN{O}_3$

Answer 1

The correct option is D $HN{O}_3$

The inertness exhibited by metals under conditions in which chemical activity is expected is known as passivity. The phenomenone of passivity is explained by assuming the formation of a thin film of oxide on the surface of the metal which prevents the action of the reagent. The concentrated nitric acid makes metals such as Fe, Co, Ni, Cr, Al, etc., passive.