Question

A gas mixture of Ne and Ar has a total pressure of 4.00 atm and contains 16.0 mol of gas. If the partial pressure of Ne is 2.75 atm, how many moles of Ar are in the mixture?
A) 11.0
B) 5.00
C) 6.75
D) 9.25
E) 12.0

Answer 1

Answer:

5 moles of Argon is present in the mixture.

Explanation:

Total pressure of the gaseous mixture = 4 atm

Total number of moles = 16

Partial pressure of Ne = 2.75 atm

By Dalton's law of partial pressure, the total pressure of gaseous mixture is the sum of partial pressures of individual gases which are non-reactive.

Hence:

$P_{total}=P_{Ar}+P_{Ne}\\4=P_{Ar}+2.75\\P_{Ar}=1.25\ atm$

Also :

Partial pressure = mole fraction*total pressure

$P_{Ar}=X_{Ar}P_{total}$

$X_{Ar}=\frac{1.25}{4}=0.3125$

$\frac{n_{Ar}}{n_{total}}=0.3125\\n_{Ar}=5$

∴Number of moles of Argon = 5