Question

How many moles of aluminum are needed to make 9 moles of molecular hydrogen? given the reaction: 2 al + 6 hcl → 2 alcl3 + 3h2 6 moles 4 moles 3 moles 2 moles none of the above?

Answer 1

1) Chemical equation

2Al + 6 HCl ---> 2Al Cl3 + 3 H2

2) molar ratios

2 mol Al : 3 moles H2

3) Proportion

2 mol Al /  3mol H2 = x / 9 mol H2

4) Solve for x

x = 9 mol H2 * 2 mol Al / 3 mol H2 = 6 mol Ag

Answer: 6 moles