Question

Which one of the equations below is an exothermic reaction?

A) CO₂ (g) → C (s) + O₂ (g) ΔH° = 394 kJ/mol
B) CaO (s) + H₂O (l) → Ca(OH)₂ (aq) ΔH° = -64 kJ/mol
C) C (s) + 2 F₂ (g) → CF₄ (g) ΔH° = 141.3 kJ/mol
D) N₂ (g) + O₂ (g) → 2 NO (g) ΔH° = 180.6 kJ/mol

Answer 1

The exothermic reaction is CaO (s) + H₂O (l) → Ca(OH)₂ (aq).

Step-by-step explanation:

An exothermic reaction is one that releases heat or energy to the surroundings. To determine which one of the equations is an exothermic reaction, we need to look at the enthalpy change (ΔH). If the value of ΔH is negative, then the reaction is exothermic.

Looking at the given equations:

• A) CO₂ (g) → C (s) + O₂ (g) ΔH° = 394 kJ/mol - This reaction is not exothermic because the value of ΔH is positive.
• B) CaO (s) + H₂O (l) → Ca(OH)₂ (aq) ΔH° = -64 kJ/mol - This reaction is exothermic because the value of ΔH is negative.
• C) C (s) + 2 F₂ (g) → CF₄ (g) ΔH° = 141.3 kJ/mol - This reaction is not exothermic because the value of ΔH is positive.
• D) N₂ (g) + O₂ (g) → 2 NO (g) ΔH° = 180.6 kJ/mol - This reaction is not exothermic because the value of ΔH is positive.