Solving for a reactant

Question

Ammonia (NH3) chemically reacts with oxygen gas (O2) to produce nitric oxide (NO) and water (H2O).

What mass of ammonia is consumed by the reaction of 5.91 g of oxygen gas?

Be sure your answer has the correct number of significant digits.

Answer 1

Hello!

This is a stoichiometry problem. The first step is to write a balanced chemical equation for this reaction.

This equation would be 4 NH₃ + 5 O₂ → 4 NO + 6 H₂O.

The key part to notice is the molar ratio of ammonia (NH₃) to oxygen gas (O₂).

This ratio is 4:5. This will be used as a conversion factor.

Next, we need to convert grams of O₂ to moles using the molar mass of O₂ which is 32 g/mol.

This gives us 0.1846875 mol O₂ (we will round at the end).

Next, we convert moles of O₂ to moles of NH₃ using the ratio previously stated.

This will give us 0.14775 moles of NH₃.

Now we convert the moles of NH₃ to grams of NH₃ and will round to 3 sig figs.

The molar mass of NH₃ is 17.03 g/mol. Our grams of NH₃ is 2.5161825, and rounding to 3 sig figs the answer would be 2.52 g of ammonia are consumed in this reaction.