If 40.0 g of HCl react with an excess of magnesium metal, what is the theoretical yield of hydrogen?

Balanced equation: Mg+2HCl=MgCl2 + H2

Showing that if Mg is not a limiting factor then 2 moles of HCl on complete reaction liberate 1 mole of Hydrogen

therefore:

1 mole of HCl=35.5g, 40g=x

X = 40/35.5 = 1.127mole

2 moles of HCl = 1 moles of Hydrogen

1.127=X

X=1.127/2 = 0.56

the theoretical yield of hydrogen