Question

The molar mass of H2O is 18.01 g/mol. The molar mass of O2 is 32.00 g/mol. What mass of H2O, in grams, must react to produce 50.00 g of O2?

Answer 1

112.5 g. The production of 50.00 g O2 requires 112.5 g H2O.

a) Write the partially balanced equation for the decomposition of water.

MM = 18.02 32.00

2H2O → O2 + …

Mass/g = 50.00

b) Calculate the moles of O2

Moles of O2 = 50.00 g O2 × (1 mol O2/16.00 g O2) = 3.1250 mol O2

c) Calculate the moles of water

Moles of H2O = 3.1250 mol O2 × (2 mol H2O/1 mol O2)

= 6.2500 mol H2O

d) Calculate the mass of water

Mass of H2O = 6.2500 mol H2O × (18.02 g H2O/1 mol H2O)

= 112.5 g H2O