Question

The diagram below shows the collection of H2 gas over water at 25°C. The total pressure in the tube is 760.0 torr. What is the pressure exerted by the hydrogen gas alone? (Hint: water vapor pressure = 23.8 torr @ 25°C)

Answer 1

Answer: 736.2 torr

Explanation: According to Dalton's law, the total pressure of a mixture of gases is the sum of individual pressures exerted by the constituent gases.

$p_{total}=p_A+p_B$

Thus $p_{total}=p_{H_2O}+p_{H_2}$

Given: $p_{total}=760 torr$

$p_{H_2O}=23.8torr$

$p_{H_2}= ?torr$

Thus $760torr=23.8torr+p_{H_2}$

$p_{H_2}=736.2torr$

Thus pressure exerted by the hydrogen gas alone is 736.2 torr.