Question

A colourless, neutral, paramagnetic oxide of Nitrogen ‘P’ on oxidation gives reddish brown gas Q. Q on cooling gives colourless gas R. R on reaction with P gives blue solid S. Identify P, Q, R, S respectively

• A. N₂O NO NO₂ N₂O₅
• B. N₂O NO₂ N₂O₄ N₂O₃
• C. NO NO₂ N₂O₄ N₂O₃
• D. NO NO N₂O₄ N₂O₅

Answer 1

The Correct Option is C

1. Identify the Key Properties of P

P is described as:
- Colorless
- Neutral
- Paramagnetic
- Oxide of Nitrogen

2. Evaluate Possible Nitrogen Oxides Based on the Properties of P

- $N_2O$: Colorless, neutral, diamagnetic.
- $NO$: Colorless, neutral, paramagnetic.
- $NO_2$: Reddish brown, acidic, paramagnetic.
- $N_2O_4$: Colorless, acidic, diamagnetic.
- $N_2O_5$: Colorless solid, acidic, diamagnetic.
- $N_2O_3$: Blue solid, acidic, diamagnetic.

Based on these properties, P must be $NO$.

3. Determine the Identity of Q
Q is formed by oxidation of P ($NO$) and is a reddish-brown gas. $NO$, when oxidized, forms $NO_2$, which is a reddish-brown gas:
$$ 2NO + O_2 \rightarrow 2NO_2 $$
Therefore, Q is $NO_2$.

4. Determine the Identity of R
Q ($NO_2$) on cooling gives a colorless gas R. $NO_2$ dimerizes at low temperatures to form $N_2O_4$, which is colorless.
$$ 2NO_2 \rightleftharpoons N_2O_4 $$
Therefore, R is $N_2O_4$.

5. Determine the Identity of S
R ($N_2O_4$) on reaction with P ($NO$) gives a blue solid S. $NO$ reacts with $N_2O_4$ to give $N_2O_3$, which is a blue solid.
$$ NO + N_2O_4 \rightarrow N_2O_3 $$
Therefore, S is $N_2O_3$.

6. Summarize the Identities of P, Q, R, and S

- P = $NO$
- Q = $NO_2$
- R = $N_2O_4$
- S = $N_2O_3$

7. Compare with the Given Options
The set of compounds matches option (C).

Final Answer:
(C) $NO$ $NO_2$ $N_2O_4$ $N_2O_3$

Answer 2

The paramagnetic oxide of nitrogen P is nitric oxide (NO). Upon oxidation, NO reacts with oxygen to form nitrogen dioxide (NO₂), which is a reddish-brown gas (Q).

• When NO₂ cools, it dissociates to form dinitrogen tetroxide (N₂O₄), which is a colorless gas (R).
• When NO reacts with N₂O₄ (R), it forms dinitrogen trioxide (N₂O₃), which is a blue solid (S).

So, the correct answer is (C) : NO NO₂ N₂O₄ N₂O₃.