Given the thermochemical equation: 2H2(g) + O2(g) → 2H2O(l)ΔH = -571.6 kJ, what is the heat of reaction (ΔH) for the formation of 1 mole of H2O(l)?

• A. -285.8 kJ
• B. +571.6 kJ
• C. -571.6 kJ
• D. +285.8 kJ

Answer: (A)

Verified step by step guidance

1. Identify the given thermochemical equation: 2H2(g) + O2(g) → 2H2O(l) with ΔH = -571.6 kJ. This means that when 2 moles of H2O are formed, 571.6 kJ of heat is released (exothermic reaction).
2. Understand that the ΔH value corresponds to the formation of 2 moles of H2O. To find the heat of reaction for the formation of 1 mole of H2O, you need to find the heat change per mole.
3. Set up a proportion to calculate the heat of reaction for 1 mole of H2O: If 2 moles release -571.6 kJ, then 1 mole will release half of that amount.
4. Calculate the heat of reaction per mole by dividing the total ΔH by 2: \( \Delta H_{1 mole} = \frac{-571.6\ \text{kJ}}{2} \).
5. Interpret the sign of ΔH: Since the original reaction is exothermic (negative ΔH), the heat of formation for 1 mole of H2O will also be negative, indicating heat is released.