An oxygen gas container has a volume of 20.0 L. How many grams of oxygen are in the container if the gas has a pressure of 876 mmHg at 23 C?

Jan 8, 2018

There are $30.4$ grams of oxygen in the sample.

Explanation:

Use the ideal gas law. We are given the pressure, the temperature and the volume. The gas constant will be $62.36$

$P V = n R T$

We're looking for $n$, the number of moles in the sample. Note that 23˚C= 23 + 273 = 296K

$\left(20.0 L\right) \left(876 m m H g\right) = n \left(62.36 m m H g L {k}^{-} 1 m o {l}^{-} 1\right) 296 K$

If we cancel all units we're left with

$n = 0.949$ mol

Knowing that

"molar mass" = ("number of grams per sample")/("number of moles")

And that the molar mass of oxygen is $32.00 \frac{g}{m o l}$, we can solve for number of grams in sample.

$32.00 \frac{g}{m o l} \cdot 0.949 m o l = g$

$g = 30.4 \text{ grams}$

Notice I rounded to $3$ sig figs.

Hopefully this helps!