If you burn 32.7 g of hydrogen and produce 292 g of water, how much oxygen reacted?

Answer 1

Here, we need to assume that all the hydrogen reacted to produce water.

The balanced chemical reaction is 2H₂ + O₂ → 2 H₂O It is interpreted as follows :

2 moles of hydrogen reacts with one mole of oxygen gas to produce 2 moles of water.

Calculate the number of moles of hydrogen used and the number of moles of water produced. The molar masses of hydrogen gas is 2.02 g/mol; oxygen is 32.0 g/mol and that of water is 18.02 g/mol.

moles of H₂ used = 32.7 g *( 1 mol H₂ /2.02 g H₂) = 16.2 mol H₂

moles of water produced = 292 g H₂O * ( 1 mol H₂O/18.02 g H₂O) = 16.2 mol H₂O

If all the H₂ reacted then the amount of moles of water formed would be calculated as follows:

grams H₂ → mol H₂ → mol H₂O

(32.7 g H₂ ) *( 1 mol H₂ / 2.02 g H₂)* ( 2mol H₂O / 2 mol H₂) = 16.2 mol of water

Moles of oxygen reacted can be determined from the stoichiometry of the reaction as follows:

16.2 mol H2O )* ( 1 mol O₂ / 2 mol H₂O) =8.10 mol O₂

Grams of oxygen = 8.10 mol O₂ * (32.0 g O₂ / 1 mol O₂ ) = 259 g oxygen

Hope this helps!