Question

Which of the following changes exhibit that nitrogen undergoes oxidation?

• A. $NH_4 \longrightarrow N_2$
• B. $NO_2 \longrightarrow NO$
• C. $NO_2 \longrightarrow NO_2$
• D. $NO_3 \longrightarrow NH_4$

Answer 1

Answer: (A)

Option (A)

Answer 2

To determine which change exhibits nitrogen undergoing oxidation, we need to calculate the oxidation states of nitrogen in each compound:

1. For Option (A):

   • In $NH_4^+$, nitrogen has an oxidation state of -3 (since 4(+1) + (-3) = +1 overall).
   • In $N_2$, as an elemental molecule, nitrogen has an oxidation state of 0.
   • Change: from -3 to 0 indicates an increase in oxidation state → oxidation.

2. For Option (B):

   • In $NO_2$, nitrogen is +4 (x + 2(-2) = 0 ⟹ x = +4).
   • In $NO$, nitrogen is +2 (x + (-2) = 0 ⟹ x = +2).
   • Change: from +4 to +2 indicates a decrease in oxidation state → reduction.

3. For Option (C):

   • $NO_2$ to $NO_2$ shows no change in oxidation state.

4. For Option (D):

   • In $NO_3^-$, nitrogen is +5 (x + 3(-2) = -1 ⟹ x = +5).
   • In $NH_4^+$, nitrogen is -3.
   • Change: from +5 to -3 indicates a decrease in oxidation state → reduction.

Thus, only option (A) $NH_4^+ \longrightarrow N_2$ exhibits oxidation because the oxidation state of nitrogen increases.