Question

What is the partial pressure of oxygen collected over water if the temperature is 20.0°C and the total gas pressure is 735 mmHg?

Answer 1

`"718 mmHg"`

Explanation:

The trick here is to realize that the oxygen, which is collected over water, will be mixed with water vapor.

This means that the *total pressure8 of the mixture will have two components

• the partial pressure of oxygen
• the vapor pressure of water at `20.0^@"C"`

The vapor pressure of water at that temperature is approximately `"14.47 mmHg"`

http://www.endmemo.com/chem/vaporpressurewater.php

This means that you will have

`P_"total" = P_"oxygen" + P_"water"`

`P_"oxygen" = "735 mmHg" - "17.47 mmHg" = color(green)("718 mmHg")`