Question

When H2(g) reacts with F2(g) to form HF(g) , 542 kJ of energy are evolved for each mole of H2(g) that reacts. Write a balanced thermochemical equation for the reaction with an energy term in kJ as part of the equation.

Answer 1

Answer:

H₂(g) + F₂(g) ⇒ 2 HF(g)   ΔH°rxn = -542 kJ

Explanation:

Let's consider the unbalanced equation that occcurs when H₂(g) reacts with F₂(g) to form HF(g).

H₂(g) + F₂(g) ⇒ HF(g)

In order to get the balanced equation, we will multiply HF(g) by 2.

H₂(g) + F₂(g) ⇒ 2 HF(g)

To convert a balanced equation into a thermochemical equation, we need to add the standard enthaply of the reaction, considering that 542 kJ of energy are evolved for each mole of H₂(g) and there is 1 mole of H₂(g) in the balanced equation. By convention, when energy is released, it takes a negative sign. The thermochemical equation is:

H₂(g) + F₂(g) ⇒ 2 HF(g)   ΔH°rxn = -542 kJ