# A cylinder of argon gas contains 50.0 L of Ar at 18.4 atm and 127 °C. How many moles of argon are in the cylinder?

Feb 19, 2016

The cylinder contains $\text{28.0 mol Ar}$.

#### Explanation:

Use the ideal gas law.

$P V = n R T$, where $n$ is moles and $R$ is the gas constant.

Known
$P = \text{18.4 atm}$
$V = \text{50.0 L}$
$T = {127}^{\circ} \text{C+273.15=400 K}$
$R = {\text{L atm K"^(-1) "mol}}^{- 1}$
https://en.m.wikipedia.org/wiki/Gas_constant

Unknown
$n$

Solution
Rearrange the equation to isolate $n$. Substitute the known values into the equation and solve for $n$.

$P V = n R T$

$n = \frac{P V}{R T}$

n=(18.4cancel"atm" * 50.0cancel"L")/(0.082057338 cancel"L" * cancel"atm" * cancel"K"^(-1) * "mol"^(-1) * 400"K")="28.0 mol Ar"