# A sample of hydrogen has a volume of 1107 mL when the temperature is 101.9 degC and the pressure is 0.867 atm. What will be the volume of the gas at STP?

Jan 2, 2016

The combined gas law holds that for a given quantity of gas:

$\frac{{P}_{1} {V}_{1}}{T} _ 1 = \frac{{P}_{2} {V}_{2}}{T} _ 2$

#### Explanation:

We use an absolute scale of temperature, ${0}^{\circ}$ $C$ $=$ $273$ $K$.

So ${V}_{2}$ $=$ $\frac{{P}_{1} {T}_{2} {V}_{1}}{{P}_{2} {T}_{1}}$ $=$

$\left(\frac{0.867 \cdot a t m}{0.987 \cdot a t m}\right) \times \left(1107 \cdot m L\right) \times \frac{273 \cdot K}{375.1 \cdot K}$ $=$ ?? $m L$.

The volume should reasonably decrease even though the pressure increases marginally. Note that I am perfectly justified in retaining non-standard units such as atmospheres and millilitres in that these cancel out. I must use the absolute temperature scale.