Question

Consider a solution of CO$_2$(g) dissolved in water in a closed container. Which one of the following plots correctly represents variation of $\log$ (partial pressure of CO$_2$ in vapour phase above water) [y-axis] with $\log$ (mole fraction of CO$_2$ in water) [x-axis] at
 $25^\circ$C? 

• A. A
• B. B
• C. C
• D. D

Hint:

Henry’s law gives a direct proportionality between partial pressure and mole fraction, resulting in a straight-line graph on a log–log plot.

Answer 1

The Correct Option is A

Step 1: Apply Henry's law.
For a gas dissolved in a liquid at constant temperature: \[ P = k_H x \] where $P$ is the partial pressure of the gas and $x$ is its mole fraction in solution.
Step 2: Take logarithm of both sides.
\[ \log P = \log k_H + \log x \] This is a linear equation of the form: \[ y = x + c \] Step 3: Interpret the graph.
- Slope $=1$
- Straight line
- Positive intercept on y-axis
Thus, the correct plot is a straight line with positive slope and non-zero intercept.
Final Answer: $\boxed{\text{Option (A)}}$