Calculate the molecular weight of hydrogen fluoride if density of this gas is 3.17 g/L at 300K and 1.0 atm pressure. What information can you deduce from the result?

PLACEHOLDER ANSWER - the question has a number and a deduction. From $$PM = dRT$$, $$M = \frac{3.17 \times 0.0821 \times 300}{1.0} \approx 78\text{ g mol}^{-1}$$. The formula mass of HF is 20, so the gas behaves as if its molecules were about four times heavier. This shows that HF molecules are associated through hydrogen bonding into clusters such as $$(\text{HF})_4$$ under these conditions.