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: Understand the reagent.
Nitric acid is a strong oxidiser. The gas it gives off depends on how concentrated the acid is and how reactive the metal is.

Step 2: Note the two metals.
Copper is below hydrogen in reactivity, while zinc is above hydrogen and more reactive. Both are treated with dilute nitric acid.

Step 3: Reaction of copper.
Less reactive copper reduces dilute nitric acid only to nitric oxide gas, NO. \[ 3Cu + 8HNO_3 \longrightarrow 3Cu(NO_3)_2 + 2NO + 4H_2O \]

Step 4: Reaction of zinc.
More reactive zinc reduces dilute nitric acid further, all the way to nitrous oxide gas, $N_2O$. \[ 4Zn + 10HNO_3 \longrightarrow 4Zn(NO_3)_2 + N_2O + 5H_2O \]

Step 5: List the products in order.
So copper gives NO and zinc gives $N_2O$, in that order.

Step 6: State the answer.
The reduction products are NO and $N_2O$ respectively. \[ \boxed{NO,\ N_2O} \]