# Question 32f13

Feb 14, 2016

The volume is 410 L.

#### Explanation:

You know that $\text{1 mol = 22.4 L}$.

Then your conversion factor is either $\text{1 mol"/"22.4 L}$ or $\text{22.4 L"/"1 mol}$.

You choose the one that cancels the given unit and gives the desired unit in the answer.

You are given "mol", so you choose the one with "mol" on the bottom..

18.3 color(red)(cancel(color(black)("mol"))) × "22.4 L"/(1 color(red)(cancel(color(black)("mol")))) = "410 L"#

Notice how the "mol" cancels and gives you the unit "L" in your answer.

If you had chosen the other factor, you would have gotten

$\text{18.3 mol" × "1 mol"/"22.4 L" = "0.818 mol"^2"/L}$, which is clearly wrong.

That's why you should use units in your calculations: if you get the wrong units in your answer, you know you have done something wrong.

NOTE: You are using the old definition of STP. Since 1982, STP has been defined as 0 °C and a pressure of 1 bar.

The volume of 1 mol of a gas at STP is 22.7 L.