Question

What is the partial pressure of helium gas in a mixture that contains 8.00 grams of helium and 8.60 mol argon gas with a total pressure of 48.0 torr?
Multiple Choice
9.06 torr
15.2 torr
23.1 torr
38.9 torr​

Answer 1

Answer:

$P_{He}=9.06torr$

Explanation:

Hello there!

In this case, we can identify the solution to this problem via the Dalton's rule because the partial pressure of helium is given by:

$P_{He}=x_{He}P_T$

Whereas the mole fraction of helium is calculated by firstly obtaining the moles and then the mole fraction:

$n_{He}=8.00g\frac{1mol}{4.00g}=2.00mol\\\\ x_{He}=\frac{n_{He}}{n_{He}+n_{Ar}} \\\\ x_{He}=\frac{2.00mol}{2.00mol+8.60mol}\\\\x_{He}=0.189$

Then, we calculate the partial pressure as shown below:

$P_{He}=0.189 *48.0torr\\\\P_{He}=9.06torr$

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