Question

A mixture of gases exists in a sealed container with the following percentages each : helium:40%, neon 50%, and argon 10%. If the total pressure of the gases is 1100 $torr$, then which of the following is true about these gases?

• A. The partial pressure of the argon gas is 21.56 $torr$.
• B. The partial pressure of the neon gas is 21.56 $torr$.
• C. The partial pressure of the neon gas is 550 $torr$.
• D. The partial pressure of the argon gas is 100 $torr$.
• E. The partial pressures of the gases cannot be calculated with the given information

Answer 1

The correct option is A The partial pressure of the argon gas is 21.56 $torr$.

The partial pressure of a gas can from the mole fraction of each gas and total pressure.

Number of moles of $40$% $He=\frac{40}{4}=10mol$

Number of moles of $50$% $Ne=\frac{50}{20}=2.5mol$

Number of moles of $50$% $Ar=\frac{10}{40}=0.25mol$

$\frac{P_{He}^o}{P}=\frac{n_{He}}{n_{total}}$

$\Rightarrow P_{He}^o=\frac{10}{10+2.5+0.25}\times 1100=862.75torr$

$\Rightarrow P_{Ne}^o=\frac{2.5}{10+2.5+0.25}\times 1100=215.7torr$

$\Rightarrow P_{Ar}^o=\frac{0.25}{10+2.5+0.25}\times 1100=21.56torr$

Note: $PV=nRT$
(A) Volume and temperature have a direct relationship
(B) Volume and pressure have an inversely proportional relationship.