Using a chemical equation to find moles of product from moles

Question

Ammonium perchlorate NH4ClO4 is a powerful solid rocket fuel, used in the Space Shuttle boosters. It decomposes into nitrogen N2 gas, chlorine Cl2 gas, oxygen O2 gas and water vapor, releasing a great deal of energy. Calculate the moles of ammonium perchlorate needed to produce 1.8mol of oxygen. Be sure your answer has a unit symbol, if necessary, and round it to the correct number of significant digits.

Answer 1

First, write the correctly balanced equation for the reaction taking place:

2 NH₄ClO₄ ==> N₂(g) + Cl₂(g) + 2 O₂(g) + 4 H₂O(g) ... balanced equation

Use dimensional analysis and the mol ratio (stoichiometry) of the balanced equation to find the mols of NH₄ClO₄ needed to produce 1.8 mol of O₂:

1.8 mol O₂ x 2 mol NH₄ClO₄ / 2 mol O₂ = 1.8 mol NH₄ClO₄ needed (2 sig. figs.)