Chemistry help with % yeild?

Question

What is the % yield when 12 g of Mg react with HCl to produce 0.2 g of H2?

Answer 1

The reaction is:

Mg + 2HCl ---->  MgCl2 + H2

The molar mass of Mg is 24.3 g/mol.

12 g Mg x (1 mol / 24.3 g) = 0.494 mol Mg

1 mol Mg produces 1 mol H2

0.494 mol Mg x (1 mol H2 / 1 mol Mg) = 0.494 mol H2

The molar mass of H2 is 2.016 g/mol.

0.494 mol H2 x (2.016 g / 1 mol ) = 0.996 g H2

% yield = (actual yield / theoretical yield) x 100

% yield = (0.2 g / 0.996 g ) x 100 = 20.0 %