If 3.18 x 1023 atoms of iron react with 67.2 L of chlorine gas at STP, what is the maximum number of grams of iron (III) chloride that can be produced?

Answer 1

so, you have
3.18/6.02 = 0.528 moles of Fe
67.2/22.4 = 3 moles of Cl2
Now look at your equation to see which is the limiting reagent, and thus determine the moles and grams of product.