Ideal Gas Example Problem - Partial Pressure

A balloon contains 0.1 moles of oxygen and 0.4 moles of nitrogen. If the balloon is at standard temperature and pressure, what is the partial pressure of the nitrogen?

Solution

Partial pressure is found by Dalton's Law

P_x = P_Total ( n_x / n_Total )

where
P_x = partial pressure of gas x
P_Total = total pressure of all gases
n_x = number of moles of gas x
n_Total = number of moles of all gases

Step 1

Find P_Total

Standard pressure is 1 atm

Step 2

Find n_Total

n_Total = n_oxygen + n_nitrogen
n_Total = 0.1 mol + 0.4 mol
n_Total = 0.5 mol

Step 3

Solve for P_nitrogen

P_nitrogen = P_Total ( n_nitrogen / n_Total )
P_nitrogen = 1 atm ( 0.4 mol / 0.5 mol )
P_nitrogen = 0.8 atm

Answer

The partial pressure of the nitrogen is 0.8 atm.