# What volume does a "5.0-g" sample of hydrogen gas occupy at STP?

## The molar volume of a gas at STP $= {\text{22.4 L mol}}^{- 1}$

Mar 5, 2017

$\text{56 L}$

#### Explanation:

The problem provides you with the molar volume of a gas at STP

${V}_{\text{n STP" = "22.4 L mol}}^{- 1}$

So, you know that under STP conditions for pressure and temperature, $1$ mole of any ideal gas will occupy $\text{22.4 L}$.

You can use the molar volume of a gas at STP as a conversion factor to help you determine the volume a sample of gas will occupy when kept under STP conditions.

In your case, you need to find volume, so rearrange the molar volume of a gas as

${\text{22.4 L"/"1 mole H}}_{2} \to$ this takes you from moles of ${\text{H}}_{2}$ to liters

Now, in order to find the number of moles present in $\text{5.0 g}$ of hydrogen gas, you can use the gas' molar mass

5.0 color(red)(cancel(color(black)("g"))) * "1 mole H"_2/(2.016color(red)(cancel(color(black)("g")))) = "2.48 moles H"_2

This sample of hydrogen gas will thus occupy

$2.48 \textcolor{red}{\cancel{\textcolor{b l a c k}{\text{moles H"_2))) * "22.4 L"/(1color(red)(cancel(color(black)("mole H"_2)))) = color(darkgreen)(ul(color(black)("56 L}}}}$

The answer is rounded to two sig figs, the number of sig figs you have for the mass of hydrogen gas.