Question

Determine the partial pressure of oxygen collected by water displacement if the water temperature is 20.0°C and the total pressure of the gases in the collection bottle is 730.0 torr.

Answer 1

In order to find the partial pressure of Oxygen gas, we need to use the partial pressure formula, which is:

Ptotal = PO2 + PH2O

This formula tell us that the total pressure of the container is the sum of all partial pressures in it, both O2 and H2O

But in this question, we only have the total pressure, 730 torr and the temperature of water, 20°C, therefore we need to find the partial pressure of water, and this can be done by looking at experimental values of vapor pressure in this specific temperature, and the value in mmHg is 17.5 at 20°C

Now we have the total pressure, 730 torr, and the partial pressure of water, 17.5 torr or mmHg (1 torr = 1 mmHg), now we can find the partial pressure of O2

Ptotal = PO2 + PH2O

730 = PO2 + 17.5

PO2 = 730 - 17.5

PO2 = 712.5 torr