Question

Ammonium perchlorate NH4ClO4 is the solid rocket fuel used by the U.S. Space Shuttle. It reacts with itself to produce nitrogen gas N2, chlorine gas Cl2, oxygen gas O2, water H2O, and a great deal of energy. What mass of nitrogen gas is produced by the reaction of 9.7g of ammonium perchlorate? Round your answer to 2 significant digits.

Answer 1

ANSWER 1.2g of nitrogen gas is produced.

Step 1: Find the moles of ammonium perchlorate consumed. You'll need the molar mass of ammonium perchlorate: 1 ×molar mass of N 4 ×molar mass of H 1 ×molar mass of Cl + 4 ×molar mass of O 1molar mass of NH4ClO4 1 ×14.0067·gmol−1 4 ×1.00794·gmol−1 1 ×35.453·gmol−1 + 4 ×15.9994·gmol−1 117.48906·gmol−1 Note: Be sure you use the atomic masses from the ALEKS Calculator or ALEKS Periodic Table and do not round early so that your answer has the correct number of significant digits. Use the molar mass to convert grams of ammonium perchlorate consumed to moles of ammonium perchlorate produced: moles of NH4ClO4 consumed = (mass of NH4ClO4 consumed) (molar mass of NH4ClO4) = 9.7g117.48906·gmol−1 = 0.08256...mol. There are 2 significant digits in 9.7g. That means there are 2 significant digits in your calculated answer for moles of ammonium perchlorate. However, keep a few extra digits for now and only round your final answer. 

Step 2: Find the moles of nitrogen gas produced. Multiply the moles of ammonium perchlorate consumed by the mole ratio: moles of N2 produced = (moles of NH4ClO4 consumed) × (moles of N2 produced) (moles of NH4ClO4 consumed) = ×0.08256mol12 = 0.04128...mol. Because stoichiometric coefficients are exact numbers, the number of moles of nitrogen gas has the same number of significant digits as the number of moles of ammonium perchlorate. 

Step 3: Find the mass of nitrogen gas produced. You'll need the molar mass of nitrogen gas: 2 ×molar mass of N 1molar mass of N2 2 ×14.0067·gmol−1 28.0134·gmol−1 Use the molar mass to convert moles of nitrogen gas produced to grams of nitrogen gas produced: mass of N2 produced = (moles of N2 produced) × (molar mass of N2) = ×0.04128mol28.0134·gmol−1 = 1.15639...g. 

There are 2 significant digits in your calculated answer for moles of nitrogen gas. 

ANSWER 1.2g of nitrogen gas is produced.