Magnesium in grams = 40 Actual yield is 1.70grams Calculating the yield based on the equation and moles, = 40g of Mn x (H2 (2.018g) / Mg (24.3g)) = 40 x 0.083 g H2 = 3.32g H2 Hydrogen % yield = (actual yield / calculated yield) x 100 = (1.70 / 3.32) x 100 Hydrogen % yield = 51.2%