Don’t really understand on how to do this.

3) 333.75 Grams

Explanation:

2Al + 6HCl --- 2AlCl3 + 3H2

Work out and label what we know and workout Ar and Mr

Al = 67.15grams         AlCl3

Al = Ar=27                  Mr = 133.5

Mass/Mr == Moles

Al = 2.5 Moles          AlCl3 = 333.75

Moles * Mr = Mass

2.5 * 133.5 = 333.75 Grams

4) Apply the same concept (numbers in front of elements are ratios, in this case 12 and 8) (when working out MR/AR ignore numbers in front)

1) Workout Mr/Ar (The relative atomic masses added up)

2) Do 36.72/(Mr of O2) = Your Moles

3) Do workout what the moles would be in the ratio 12:8 (Times/divide moles to find out the correct moles for 12:8

4) Times the new moles by the Mr of SO3

5) = Answer