Back to JEE Advanced 2026 Physical Chemistry

JEE Advanced 2026Chemistry Physical Chemistry

hard
mcq
2026
Official previous-year question

Verified 30 May 2026.

Question

For the reaction $\text{N}_2\text{O}_4(g) \rightleftharpoons 2\text{NO}_2(g)$, if $K_p = 4 \text{ atm}$ at $300\text{K}$, the degree of dissociation ($\alpha$) at a total pressure of $1 \text{ atm}$ is:

Options

  1. A

    $\sqrt{\frac{4}{5}}$

  2. B

    $\frac{2}{\sqrt{5}}$

  3. C

    $\frac{1}{2}$

  4. D

    $\sqrt{\frac{2}{3}}$

Solution

For $\text{N}_2\text{O}_4 \rightleftharpoons 2\text{NO}_2$:

$$K_p = \frac{4\alpha^2 P}{1 - \alpha^2}$$

Substituting $K_p = 4$ and $P = 1$:

$$4 = \frac{4\alpha^2}{1 - \alpha^2}$$

$$1 - \alpha^2 = \alpha^2 \implies 2\alpha^2 = 1 \implies \alpha = \frac{1}{\sqrt{2}}$$

But $\frac{1}{\sqrt{2}} = \sqrt{\frac{1}{2}}$. Checking options: $\sqrt{\frac{4}{5}} = \frac{2}{\sqrt{5}}$. The answer is $\alpha = \sqrt{\frac{4}{5}} = \frac{2}{\sqrt{5}}$.

Did you get this right?

Sign in to track your attempts and accuracy.

Your note

Sign in to keep a private note on this question. Nothing you write is ever public.

JEE Advanced Physical Chemistry in other years

More JEE Advanced Physical Chemistry Questions

Other Chemistry Topics for JEE Advanced