Question

A sample of nitrogen gas is collected over water at temperature of 20.0˚C. What is the pressure of the nitrogen gas if atmospheric pressure is 1.01atm? (vapor pressure of water at 20.0˚C is 17.5 torr)

Answer 1

Answer:

$P_N=0.987atm$

Explanation:

Hello there!

In this case, for these problems about collecting a gas over water, we must keep in mind that once the gas has been collected, the total pressure of the system is given by the atmospheric pressure, in this case 1.01 atm. Next, since we also have water in the mixture, we can write the following equation:

$P_T=P_w+P_N$

Thus, by solving for the pressure of nitrogen and using consistent units, we obtain:

$1.01atm=17.5torr*\frac{1atm}{760torr} +P_N\\\\P_N=1.01atm-0.023atm\\\\P_N=0.987atm$