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 3.2 g of oxygen gas? Round your answer to 2 significant digits.

Answer 1

Unbalanced equation:

NH₃ + O₂ ---> NO + H₂O

Now balancing the Hydrogen, followed by balancing Oxygen gives

2NH₃ + 2.5O₂ ---> 2NO + 3H₂O

Multiplying the entire equation by 2 gives a balanced equation

4NH₃ + 5O₂ ---> 4NO + 6H₂O

Now calculation of mass of ammonia:

Given mass of oxygen gas reacting.

Molar mass of oxygen molecule is 32 g/mole ( O₂ = 2 times atomic weight of oxygen 16 g/mole)

Thus, 3.2 g = 3.2/32 moles of oxygen = 0.1 mole

If we divide the balanced equation by 5, we get

4/5 NH₃ + 1 O₂ ---> 4/5 NO + 6/5 H₂O

Which means, one mole of oxygen reacts with 4/5 moles of ammonia.

From above calculation we know the number of moles of oxygen to be 0.1 mole. Therefor number of moles of ammonia that would react with oxygen = 0.1 * (4/5) = 0.08 moles

mass of 0.08 moles of ammonia = number of moles * molar mass of ammonia

Molar mass of ammonia = 17 g/mole

mass of 0.08 moles of ammonia = 0.08 * 17 = 1.36 g

3.2 g of oxygen gas will react with 1.36 g of ammonia, which is mass of ammonia consumed.