A gas is collected by water displacement at 25 degrees Celsius. The vapor pressure of water at that temperature is 24 mmHg. If the atmospheric pressure is 800 mmHg, then what is the pressure of the dry gas you collected
To find the pressure of the dry gas collected, we need to subtract the vapor pressure of water from the atmospheric pressure.
Given:
Vapor Pressure of water (P_water) = 24 mmHg
Atmospheric Pressure (P_atm) = 800 mmHg
By water displacement, the collected gas is saturated with water vapor, which means it contains water vapor at the vapor pressure of water at that temperature. Therefore, the total pressure observed during the experiment is the sum of the pressure contributed by the dry gas (P_dry) and the vapor pressure of water (P_water).
Total pressure (P_total) = P_dry + P_water
But we are interested in the pressure of the dry gas alone, so we can rearrange the equation as:
P_dry = P_total - P_water
Now, substituting the given values:
P_dry = P_atm - P_water
= 800 mmHg - 24 mmHg
= 776 mmHg
Therefore, the pressure of the dry gas collected is 776 mmHg.