To get the enthalpy of decomposition, reverse the equation and ΔH then divide the ΔH by 2:
2Mg(s) + O2(g) → 2MgO(s) ΔH = -1204 kJ (reverse)
2MgO(s) → 2Mg(s) + O2(g) ΔH = -1204 kJ (divide by two)
Consider this combination reaction:
2Mg(s) + O2(g) → 2MgO(s) ΔH = -1204 kJ
What is the enthalpy for the decomposition of 1 mole of MgO(s) into Mg(s) and O2(g)?
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