**Calculate the pressure of helium gas:**

${\mathbf{P}}_{\mathbf{total}}\mathbf{=}{\mathbf{P}}_{{\mathbf{CO}}_{\mathbf{2}}}\mathbf{+}{\mathbf{P}}_{\mathbf{Ar}}\mathbf{+}{\mathbf{P}}_{{\mathbf{O}}_{\mathbf{2}}}\mathbf{+}{\mathbf{P}}_{\mathbf{He}}\phantom{\rule{0ex}{0ex}}{\mathbf{P}}_{\mathbf{He}}\mathbf{=}{\mathbf{P}}_{\mathbf{total}}\mathbf{-}({P}_{{\mathrm{CO}}_{2}}+{P}_{\mathrm{Ar}}+{P}_{{O}_{2}})\phantom{\rule{0ex}{0ex}}{\mathbf{P}}_{\mathbf{He}}\mathbf{=}\mathbf{760}\mathbf{}\mathbf{mmHg}\mathbf{-}(126\mathrm{mmHg}+220\mathrm{mmHg}+188\mathrm{mmHg})$

**P _{He} = 226 mmHg**

**Calculate the pressure in atm:**

1 atm = 760 mmHg

${\mathbf{P}}_{\mathbf{He}}\mathbf{=}\mathbf{226}\mathbf{}\overline{)\mathbf{mmHg}}\mathbf{\times}\frac{\mathbf{1}\mathbf{}\mathbf{atm}}{\mathbf{760}\mathbf{}\overline{)\mathbf{mmHg}}}$

**P _{He} = 0.2974 atm**

**Ideal Gas Law:**

$\overline{)\mathbf{PV}\mathbf{=}\mathbf{nRT}}$

$\mathbf{moles}\mathbf{}\mathbf{\text{(n)}}\mathbf{=}\frac{\mathbf{mass}\mathbf{}\mathbf{\left(}\mathbf{m}\mathbf{\right)}}{\mathbf{molar}\mathbf{}\mathbf{mass}\mathbf{}\mathbf{\left(}\mathbf{M}\mathbf{\right)}}$

A gas mixture with a total pressure of 760 mmHg contains each of the following gases at the indicated partial pressures: 126 mmHg CO_{2}, 220 mmHg Ar, and 188 mmHg O_{2}. The mixture also contains helium gas.

What mass of helium gas is present in a 12.6-L sample of this mixture at 274 K ?

Frequently Asked Questions

What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Partial Pressure concept. You can view video lessons to learn Partial Pressure. Or if you need more Partial Pressure practice, you can also practice Partial Pressure practice problems.