How many grams of water are produced from the reaction of 7.51 grams of Hydrogen gas with excess oxygen
H2 + O2 —> H2O

The answer to your question is 67.5 g of H₂O

Explanation:

Data

mass of water = ?

mass of H₂ = 7.51 g

mass of O₂ = excess

Balanced chemical reaction

                2H₂  +  O₂  ⇒   2H₂O

Process

1.- Calculate the molar mass of H₂ and H₂O

H₂ = 2(1 x 2) = 4 g

H₂O = 2[(2 x 1) + (16 x 1)] = 2[18] = 36 g

2.- Use proportions and cross multiplication to find the answer

                     4 g of H₂ 36 g of H₂O

                   7.5 g of H₂    x

                           x = (7.5 x 36) / 4

                           x = 270 / 4

                           x = 67.5 g of H₂O