Question

Ammonia reacts with oxygen according to the equation: 4 NH₃ (g) + 5 O₂ (g) + 6 H₂O (g). Delta H rxn= -906 kJ

Calculate the heat (in kJ) associated with the complete reaction of 143 g of NH₃

Answer 1

Ammonia reacts with oxygen to form nitrous oxide and water according to the following reaction:

4 NH₃ (g) + 5 O₂ (g) -------> 4 NO (g)+ 6 H₂O (g). (Delta H rxn= -906 kJ)

4 mole ammonia reacts with 5 mole oxygen to form 4 moles of NO. We can calculate the number of moles from the data given.

Mass of ammonia given = 143 gm

We know, Molar mass of ammonia = 17.03 gm/mol

number of moles of ammonia = mass/molar mass

                                          = 143 gm / 17.03 gm/mol

                                          = 8.4 moles NH₃

According to the reaction, from 4 moles of ammonia -906 KJ heat is liberated.

It means, 4 mole ammonia = -906 KJ

Therefore, 8.4 moles NH₃ = -906 KJ/ 4moles * 8.4 moles

                                      = 1902.6 KJ