2H2S (g) + 3O2 (g) → 2H2O (g) + 2SO2 (g)

If 3.50 g of H2S are used in the above reaction, what will be the theoretical yield of water in grams?

There are three steps to do: 1) convert grams to moles, 2) convert moles to moles and 3) convert moles to grams

1) let's convert the 3.50 grams of H₂S to moles using the molar mass

molar mass H₂S = (2 x 1.01) + 32.0 = 34.02 g/mol

3.50 g (1 mol / 34.02 g) = 0.103 mol H₂S

2) let's convert moles of H₂S to moles of water using the mole-mole ratio from the balanced equation.

0.103 mol H₂S (2 mol H₂O / 2 mol H₂S) = 0.103 mol H₂O

3) lastly, let's convert moles of water to grams using the molar mass

molar mass of H₂O = (2 x 1.01) + 16.0 = 18.02 g/mol

0.103 mol H₂O (18.02 g / mol) = 1.85 grams of H₂O