Question

In a reaction, 4 moles of electrons are transferred to one mole of $HN{O}_3$. The possible product obtained after the reduction is:

• A. $0.5$ mole of $N_2$
• B. $0.5$ mole of $N_{2}O$
• C. $1$ mole of $N{O}_2$
• D. $1$ mole of $N_{2}O$

Answer 1

The correct option is B $0.5$ mole of $N_{2}O$

The oxidation state of $N$ in $HN{O}_3$ is +5. Number of electrons needed depends on the final oxidation state.
A) To form 0.5 mole of $N_2$, the number of moles of electrons required will be 5, since the change in the oxidation state is 5.

B) To form 0.5 mole of $N_{2}O$, the number moles of electrons required will be 4, since the change in the oxidation state is 4.

C) To form 1 mole of $N{O}_2$, the number of moles of electrons required will be 3, since the change in the oxidation state is 3.

D) To form 1 mole of $N_{2}O$, the number of moles of electrons required will be 8, since the change in the oxidation state is 4.
Hence, (b) is the correct answer.