How many grams of hydrogen cyanide (HCN) gas are there in 23.8 liters at STP?

Question

I don't know how to solve this problem and I have been working on it for the last 30 minutes or so.

Answer 1

You must MEMORIZE the fact that at STP 1 mole of any gas = 22.4 liters, and 22.4 liters of any gas = 1 mole of that gas.

Thus, 23.8 liters is more than 22.4 liters, so more than 1 mole.

23.8 liters x 1 mole/22.4 liters = 1.06 moles

1.06 moles HCN x 27 g/mole = 28.6 grams HCN  (3 significant figures)