If a sample of gas which weighs 0.400 g has a volume of 250 mL at STP, what is the molecular weight of the gas?

Jun 4, 2016

Approx. $36.0 \cdot g \cdot m o {l}^{-} 1$

Explanation:

The molar volume of an Ideal Gas at $S T P$ is $22.4 \cdot L \cdot m o {l}^{-} 1$.

We assume that the gas behaves ideally, and thus we multiply the given density $\left(g \cdot {L}^{-} 1\right)$ by the molar volume at $S T P$, to give....

$\frac{0.400 \cdot g}{0.250 \cdot \cancel{L}} \times 22.4 \cdot \cancel{L} \cdot m o {l}^{-} 1$ $=$ $35.9 \cdot g \cdot m o {l}^{-} 1$.

Given this molecular weight, the gas is quite possiby $H C l$.