Question

The reduction products formed when copper and zinc metals are separately oxidised with dilute $HNO_{3}$ respectively are

• A. NO, NO${2}$
• B. N${2}$O, NO
• C. NO, N${2}O$
• D. NO${2}$, NO

Hint:

With DILUTE $HNO_{3}$: Copper gives $NO$, while Zinc gives $N_{2}O$. With CONCENTRATED $HNO_{3}$, both metals give $NO_{2}$ gas.

Answer 1

The Correct Option is C

Step 1: Concept
Nitric acid ($HNO_{3}$) is a strong oxidizing agent. Its reduction products depend on both the concentration of the acid and the reactivity of the metal it encounters.

Step 2: Meaning
Dilute nitric acid yields different nitrogen oxide gas products based on whether the metal is less reactive than hydrogen (like $Cu$) or more reactive than hydrogen (like $Zn$).

Step 3: Analysis
With Copper ($Cu$): Copper is less reactive. When treated with dilute $HNO_{3}$, it reduces the acid to nitric oxide ($NO$) gas: $$3Cu + 8HNO_{3}\text{ (dilute)} \longrightarrow 3Cu(NO_{3})_{2} + 2NO\uparrow + 4H_{2}O$$ With Zinc ($Zn$): Zinc is a more electropositive, highly reactive metal. When treated with dilute $HNO_{3}$, it reduces the acid further down to nitrous oxide ($N_{2}O$, laughing gas): $$4Zn + 10HNO_{3}\text{ (dilute)} \longrightarrow 4Zn(NO_{3})_{2} + N_{2}O\uparrow + 5H_{2}O$$ The resulting gases from this sequential prompt are $NO$ and $N_{2}O$ respectively.

Step 4: Conclusion
This matches option (C) perfectly.

Final Answer: (C)