JEE Main 2026 — Chemistry Physical Chemistry

2026mcqeasy

Consider a solution of $\mathrm{CO}_{2}(\mathrm{~g})$ dissolved in water in a closed container. Which one of the following plots correctly represents variation of log (partial pressure of $\mathrm{CO}_{2}$ in vapour phase above water) $[y$ -axis] with $\log$ (mole fraction of $\mathrm{CO}_{2}$ in water) $[x$ -axis $]$ at $25^{\circ} \mathrm{C}$ ?

Official previous-year question

Held on 22 Jan 2026 · Verified 6 Jul 2026.

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Solution

According to Henry's Law, the partial pressure of a gas in the vapour phase ( $p$ ) is proportional to the mole fraction of the gas in the solution ( $x$ ).

The mathematical expression is: $p = K_H \cdot x$

where $K_H$ is the Henry's law constant.

Taking logarithm on both sides:

$\log(p) = \log(K_H \cdot x)$

$\log(p) = \log(K_H) + \log(x)$

Comparing this with the equation of a straight line $y = mx + c$ :

$y = \log(p)$ (y-axis)

$x = \log(x)$ (x-axis)

$m = 1$ (slope)

$c = \log(K_H)$ (y-intercept)

Since $K_H$ for $CO_2$ in water is a positive constant at $25^{\circ}C$ , $\log(K_H)$ will be a constant intercept.

The plot of $\log(p)$ vs $\log(x)$ is a straight line with a positive slope and a positive y-intercept.

This corresponds to graph (2).

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JEE Main Physical Chemistry in other years

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JEE Main 2026 — Chemistry Physical Chemistry

2026mcqeasy

Official previous-year question

Held on 22 Jan 2026 · Verified 6 Jul 2026.

Options

Did you get this right?

Solution

According to Henry's Law, the partial pressure of a gas in the vapour phase ( $p$ ) is proportional to the mole fraction of the gas in the solution ( $x$ ).

The mathematical expression is: $p = K_H \cdot x$

where $K_H$ is the Henry's law constant.

Taking logarithm on both sides:

$\log(p) = \log(K_H \cdot x)$

$\log(p) = \log(K_H) + \log(x)$

Comparing this with the equation of a straight line $y = mx + c$ :

$y = \log(p)$ (y-axis)

$x = \log(x)$ (x-axis)

$m = 1$ (slope)

$c = \log(K_H)$ (y-intercept)

Since $K_H$ for $CO_2$ in water is a positive constant at $25^{\circ}C$ , $\log(K_H)$ will be a constant intercept.

The plot of $\log(p)$ vs $\log(x)$ is a straight line with a positive slope and a positive y-intercept.

This corresponds to graph (2).

Your note

JEE Main Physical Chemistry in other years

Keep practicing Physical Chemistry

Work through every JEE Main Physical Chemistry PYQ, year by year.

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JEE Main 2026 — Chemistry Physical Chemistry

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Solution

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JEE Main Physical Chemistry in other years

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JEE Main 2026 — Chemistry Physical Chemistry

Options

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Solution

Your note

JEE Main Physical Chemistry in other years

More JEE Main Physical Chemistry questions

Other Chemistry topics for JEE Main

Organic Chemistry

Inorganic Chemistry

Keep practicing Physical Chemistry