Question

2.0 g of H2 gas reacts with 32 g of O2 gas to form water. Assuming the reaction goes to completion, how many grams of water will be produced?

Answer 1

In order to solve this problem, the balanced chemical equation of the reaction must be used. This gives the equation:

2H2 + O2 --> 2H2O

Next, the moles of the reactants must be used in order to apply their stoichiometric relationships. Note that 1 mole of oxygen needs 2 moles of hydrogen for the reaction proceed. Since there is only 1 mole of H2, only 0.5 moles of oxygen are consumed.

moles H2 = 2 g/ 2g/mol = 1 mole H2
moles O2 = 32 g/ 32g/mol = 1 mole O2

2H2 + O2 --> 2H2O
i 1 1 0
c 1 0.5 1
e 0 0.5 1

Assuming the reaction will proceed, there will be an excess of 0.5 mol O2 and a product of 1 mol H2O. This gives 18 grams of water.