Question

A sample of nitrogen is collected over water at 20°C. The vapor pressure of water at 20°C is 18 mmHg. What is the partial pressure of the nitrogen if the total pressure is 21 mmHg?

Answer 1

Not very much..........

Explanation:

`P_"total"=P_(N_2)+P_"SVP"`

Now, we are given that `P_"total"=21*mm*Hg`, and further that `P_"SVP"`, `"the saturated vapour pressure of water"` at this temperature, `=18*mm*Hg`.

So `P_(N_2)=P_"total"-P_"SVP"=(21-18)*mm*Hg=3*mm*Hg`.