Question

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?

Answer 1

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`

`PV = nRT`

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

`(20.0 L)(876 mmHg) = n(62.36 mmHg L k^-1 mol^-1)296K`

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 g/(mol)`, we can solve for number of grams in sample.

`32.00 g/(mol) * 0.949 mol = g`

`g = 30.4 " grams"`

Notice I rounded to `3` sig figs.

Hopefully this helps!