How much heat is absorbed/released when 25.00 g of NH3 (g) reacts in the presence of excess O2 (g) to produce NO (g) and H2O (l) according to the following chemical equation? 4 NH3 (g) + 5 O2 (g) → 4 NO (g) + 6 H2O (l) ΔH° = 1168 kJ

429.4 kJ are absorbed in the endothermic reaction.

Explanation:

The balanced chemical equation tells us that 1168 kJ of heat are absorbed in the reaction when 4 mol of NH₃ (g) react with 5 mol O₂ (g).

So what we need is to calculates how many moles represent 25 g NH₃ (g) and calculate the heat absorbed. (NH₃ is the limiting reagent)

Molar Mass NH₃ = 17.03 g/mol

mol NH₃ = 25.00 g / 17.03 g/mol = 1.47 mol

1168 kJ / 4 mol NH₃ x 1.47 mol NH₃ = 429.4 kJ