# What is the density of chlorine gas at 1.21 atm and 34.9°C?

Dec 9, 2016

$\rho = 3.40 \cdot g \cdot {L}^{-} 1.$

#### Explanation:

We assume (reasonably) ideal gas behaviour.

And thus $P V = n R T$, else $\frac{n}{V} = \frac{P}{R T}$

$=$ $\frac{1.21 \cdot a t m}{0.0821 \cdot L \cdot a t m \cdot {K}^{-} 1 \cdot m o {l}^{-} 1 \times 307.9 \cdot K}$

$=$ $0.0479 \cdot m o l \cdot {L}^{-} 1$.

So, we have worked out a density in $m o l \cdot {L}^{-} 1$, and we multiply this by the molecular mass in $g \cdot m o {l}^{-} 1$.

And $70.9 \cdot g \cdot m o {l}^{-} 1 \times 0.0479 \cdot m o l \cdot {L}^{-} 1 = 3.40 \cdot g \cdot {L}^{-} 1.$

From where did I get the figure $70.9 \cdot g \cdot m o {l}^{-} 1$?