# Question #777e2

May 12, 2016

The pressure is unknown. The partial pressure is a multiple of the mole fraction of each component.

#### Explanation:

We have volume, and amount of substance; we do not have temperature, which we require if pressure is to be calculated. I assume that the temperature is $298 \cdot K$.

$\text{Moles of helium:}$ $\frac{32.6 \cdot g}{4.0 \cdot g \cdot m o {l}^{-} 1} = 8 \cdot m o l$

$\text{Moles of dioxygen:}$ $\frac{51.2 \cdot g}{32.0 \cdot g \cdot m o {l}^{-} 1} = 1.6 \cdot m o l$

The total pressure $P = \frac{n R T}{V}$ $=$

$\frac{\left(8.0 + 1.6\right) \cdot m o l \times 0.0821 \cdot L \cdot a t m \cdot {K}^{-} 1 \cdot m o {l}^{-} 1 \times 298 \cdot K}{0.150 \cdot L}$ $=$ ${P}_{T}$

The partial pressure of dioxygen ${P}_{{O}_{2}} = \frac{{P}_{{O}_{2}}}{P} _ T$ $=$ $\frac{1.6 \cdot m o l}{\left(8 + 1.6\right) \cdot m o l} \times {P}_{T}$.

This sounds like a deep sea diving mix, where helium replaces dinitrogen in order to avoid the narcotic effect of dinitrogen.