Question

At 25°C, the following heats of the reaction are known:

At the same temperature, use Hess's law to calculate the standard enthalpy of the reaction.

ClF(g) + F2(g) → ClF3(g)

Answer 1

-108.7 KJ/mol

Step-by-step explanation:

Hess's law state that in a multiple stage reaction, the enthalpy change is the sum of all the enthalpy changes.

2CIF (g) + O₂ (g) → Cl₂O(g) + F₂O (g) ΔH°rxn =167.4 KJ/mol

2ClF₃(g) + 2O₂(g) → Cl₂O(g) + 3F₂O(g) ΔH°rxn = 341.4 kJ/mol

flip the above reaction

Cl₂O(g) + 3F₂O(g) → 2ClF₃(g) + 2O₂(g) ΔH°rxn = -341.4 kJ/mol

2CIF (g) + O₂ (g) → Cl₂O(g) + F₂O (g) ΔH°rxn = 167.4 KJ/mol

2F₂(g) + O₂(g) → 2F₂O(g) ΔH°rxn = –43.4 kJ/mol

add all the enthalpy change = -341.4 kJ/mol + 167.4 KJ/mol – 43.4 kJ/mol = -217.4

2CIF (g) + 2F₂(g) → 2ClF₃(g) ΔH°rxn = -217.4 KJ/mol

ClF(g) + F2(g) → ClF3(g) = (ΔH°rxn = -217.4 KJ/mol) / 2 = -108.7 KJ/mol