Question

When NH3(g) reacts with O2(g) to form N2O(g) and H2O(l) , 342 kJ of energy are evolved for each mole of NH3(g) that reacts. Write a balanced thermochemical equation for the reaction with an energy term in kJ as part of the equation. Note that the answer box for the energy term is case sensitive. Use the SMALLEST INTEGER coefficients possible and put the energy term (including the units) in the last box on the appropriate side of the equation. If a box is not needed, leave it blank.

Answer 1

Answer:

2 NH₃(g) + 2 O₂(g) ⇒ N₂O(g) + 3 H₂O(l)   ΔH° = -684 kJ

Explanation:

Let's consider the unbalanced equation that occurs when NH₃(g) reacts with O₂(g) to form N₂O(g) and H₂O(l).

NH₃(g) + O₂(g) ⇒ N₂O(g) + H₂O(l)

We will begin balancing N atoms by multiplying NH₃(g) by 2.

2 NH₃(g) + O₂(g) ⇒ N₂O(g) + H₂O(l)

Then, we will balance H atoms by multiplying H₂O(l) by 3.

2 NH₃(g) + O₂(g) ⇒ N₂O(g) + 3 H₂O(l)

Finally, we will get the balanced equation by multiplying O₂(g) by 2.

2 NH₃(g) + 2 O₂(g) ⇒ N₂O(g) + 3 H₂O(l)

Since 342 kJ of energy are evolved for each mole of NH₃(g), and there are 2 moles of NH₃(g) in the balanced equation, the heat evolved will be2 × 342 kJ = 684 kJ. By convention, when heat is evolved, it takes a negative sign. The balanced thermochemical equation is:

2 NH₃(g) + 2 O₂(g) ⇒ N₂O(g) + 3 H₂O(l)   ΔH° = -684 kJ