Calculate the density of chlorine gas in g/L, at STP

Question

I'm coming up with 3.2g/L (by using 70.9 g Cl2) Cl gas is diatomic, correct? Is this correct?

Answer 1

If you use 22.4 L/mol and you are using 70.9, doesn't that allow you three significant figures? I calculate 3.165 g/L which I would round to 3.16 g/L.