Magnesium burns in oxygen to form solid magnesium oxide according to the balanced equation

CHEMISTRY · Multi-part · A Level · Chemistry · Energetics · Energetics

Problem

Magnesium burns in oxygen to form solid magnesium oxide according to the balanced equation 2 Mg(s)+O2(g)→2 MgO(s)\mathrm{2\,Mg(s) + O_2(g) \rightarrow 2\,MgO(s)}. The standard enthalpy of formation of MgO(s)\mathrm{MgO(s)} is −601 kJ mol−1-601\,\text{kJ\,mol}^{-1}. Elements in their standard states have standard enthalpy of formation equal to zero. (a) Calculate the standard enthalpy change, in kJ, for the reaction as written. (b) Determine the standard enthalpy change, in kJ, associated with the production of exactly one mole of MgO(s)\mathrm{MgO(s)}. (c) A sample of 5.00 g5.00\,\text{g} of Mg(s)\mathrm{Mg(s)} reacts completely with excess oxygen under standard conditions. Calculate the heat released, in kJ, by this reaction. Show all steps, including molar-mass calculations and unit analysis.

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