Q. At $20℃$ and 1.00 atm partial pressure of hydrogen, 18 mL of hydrogen, measured at STP, dissolves in 1 L of water. If water at $20℃$ is exposed to a gaseous mixture having total pressure of 1400 torr (excluding the vapour pressure of water) and containing 68.5% $H_{2}$ by volume, find the volume of $H_{2}$, measured at STP, which will dissolve in 1 L of water
A) 18 mL
B) 12 mL
C) 23 mL
D) 121 mL
Explanation
(c)
$p\left( H_{2} \right) = \frac{1400 \times 68.5}{100}torr$
$= 959\ torr = 959/760\ atm$
$= 1.26\ atm$
According to Henry’s law,
amount of gas absorbed is directly proportional to pressure
Hence, $\frac{V}{18\ mL} = \frac{1.26\ atm}{1\ atm}$
$V = 23\ mL$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.