# How many moles of chlorine gas are contained in a 5.00 L flask at 27°C and .947 atm pressure?

Approx. $0.2 \cdot m o l$
$n$ $=$ $\frac{P V}{R T}$
$=$ $\frac{0.947 \cdot a t m \times 5.00 \cdot L}{0.0821 \cdot L \cdot a t m \cdot {K}^{-} 1 \cdot m o {l}^{-} 1 \times 300 \cdot K}$
If you cancel thru units you get an answer in $\text{moles}$, as required.