# If a sample of helium gas at 870 torr and 22 degrees C is allowed to expand from 23 L to 55 L without changing the temperature, what pressure will the helium gas exert?

May 25, 2018

Well, for a start...the measurement of pressure is illegitimate...

#### Explanation:

We know that one atmosphere will support a column of mercury that is $760 \cdot m m$ high. A mercury column is thus a good measure for pressures at $1 \cdot a t m$ or much LOWER than $1 \cdot a t m$..

And so here $P = \frac{870 \cdot m m \cdot H g}{760 \cdot m m \cdot H g \cdot a t {m}^{-} 1} = 1.15 \cdot a t m$.

And so ${P}_{1} {V}_{1} = {P}_{2} {V}_{2}$...and ${P}_{2} = \frac{{P}_{1} {V}_{1}}{V} _ 2$

$= \frac{1.15 \cdot a t m \times 23 \cdot L}{55 \cdot L} = 0.479 \cdot a t m \equiv 363.8 \cdot m m \cdot H g$