Question

From the given list of metals, identify the number of metals which do not dissolve in concentrated nitric acid are Cu, Al, Zn, Ni, Fe.

• A. 2
• B. 3
• C. 4
• D. 5

Hint:

Conc. HNO\(_3\) causes passivation in Al, Fe, Ni due to oxide layer formation.

Answer 1

The Correct Option is B

Step 1: Behavior with concentrated nitric acid.
Conc. HNO₃ is a potent oxidant that dissolves many metals, but some undergo passivation, forming protective oxide coatings.

Step 2: Examining each metal.
Cu dissolves; Al passivates and resists dissolution; Zn dissolves; Ni passivates; Fe passivates.

Step 3: Counting passive metals.
Al, Ni, and Fe do not readily dissolve → total = 3.

Step 4: Passivation rationale.
An adherent oxide layer shields the underlying metal from further acid attack.

Step 5: Conclusion.
The number of metals not dissolving is 3.