Question

Dry air near sea level has the following composition by volume: N2, 78.08 percent; O2, 20.94 percent; Ar, 0.93 percent; CO2, 0.05 percent. The atmospheric pressure is 1.00 atm. (Hint: Since volume is proportional to the number of moles present, mole fractions of gases can be expressed as ratios of volumes at the same temperature and pressure.)

(a) Calculate the partial pressure of each gas in atm.

(b) Calculate the concentration of each gas in moles per liter at 0°C.

Answer 1

a. The hint tells you that the mole fraction N2 = 0.7808; therefore the partial pressure of N2 = X_N2*P_total

b. I would sum the moles and use PV = nRT to calculate volume. Then M = moles/L.

Answer 2

0.781 atm