Given the thermochemical equation: 2 O_3(g) → 3 O_2(g)ΔH = -284 kJ, what is the enthalpy change for this reaction per mole of O_3(g)?

• A. -95 kJ
• B. -142 kJ
• C. -284 kJ
• D. +142 kJ

Answer: (B)

Verified step by step guidance

1. Identify the given thermochemical equation and its enthalpy change: 2 O_3(g) \rightarrow 3 O_2(g) with \Delta H = -284 \text{ kJ}. This means that when 2 moles of ozone decompose, the enthalpy change is -284 kJ.
2. Understand that the enthalpy change given corresponds to the reaction as written, which involves 2 moles of O_3. To find the enthalpy change per mole of O_3, you need to divide the total enthalpy change by the number of moles of O_3 involved.
3. Set up the calculation for enthalpy change per mole of O_3 as: \frac{\Delta H}{\text{moles of } O_3} = \frac{-284 \text{ kJ}}{2 \text{ moles}}.
4. Perform the division to find the enthalpy change per mole of O_3, which will give the value associated with the decomposition of one mole of ozone.
5. Interpret the sign of the enthalpy change: since the original \Delta H is negative, the reaction is exothermic, so the enthalpy change per mole of O_3 will also be negative.