Question

1. Consider the following properties of the atmosphere near the coast in Southern California: Average surface pressure: 1010 mbar Average temperature: 295 K Atmospheric gas composition (by volume): Nitrogen (N2) 77.0%, Oxygen (O2) 20.7%, Water (H2O) 1.4%, Argon (Ar), 0.9%. a. What is the average partial pressure of N2 in the atmosphere, pA, in units of Pa

Answer 1

Answer: The average partial pressure of $N_2$ in the atmosphere is 77770 Pa.

Explanation

Raoult's Law states that the partial pressure of each component in the mixture is equal to the total pressure multiplied by its mole fraction. It is mathematically expressed as

$p=\chi\times P$  

where, p = partial pressure

$\chi$ = mole fraction

$P$ = total pressure

mole fraction of $N_2$ = $\frac{\text {moles of} N_2}{\text {total moles}}=\frac{77.0}{77.0+20.7+1.4+0.9}=\frac{77.0}{100}=0.77$

$p_{N_2}=0.77\times 1010mbar=777.7mbar=77770Pa$    

(1 mbar=100Pa)

Thus the average partial pressure of $N_2$ in the atmosphere is 77770 Pa