enthalpy & first law

Question

For the reaction: 2C(graphite) + O2(g) → 2CO(g), ΔH = -221 kJ. What is the enthalpy change (ΔH) per mole of CO formed?

RankGuru · Accepted Answer

1. **Stoichiometry**: The balanced equation shows that $2$ moles of $CO(g)$ are produced.
2. **Enthalpy Interpretation**: The given $\Delta H = -221$ kJ is the heat released when the reaction occurs exactly as written (i.e., for $2$ moles of $CO$).
3. **Molar Enthalpy**: To find the enthalpy change per mole, we divide the total enthalpy by the number of moles of the product of interest.
4. **Calculation**: $\Delta H_{	ext{per mole}} = \frac{-221 	ext{ kJ}}{2 	ext{ moles}} = -110.5 	ext{ kJ/mol}$.
5. **Signify**: The negative sign indicates an **exothermic** process.

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enthalpy & first law

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