How many grams of magnesium must be burned to obtain 1000 kJ of heat if the enthalpy

How many grams of magnesium must be burned to obtain 1000 kJ of heat if the enthalpy of formation of magnesium oxide is – 601.8 kJ / mol

The reaction equation for the formation of magnesium oxide: Mg + 0.5O2 -> MgO. Magnesium and oxygen are simple substances, the enthalpy of their formation is zero, therefore the heat effect of the reaction is equal to deltaH = -601.8-0-0 = -601.8 kJ / mol. deltaH (combustion) = – deltaH = 601.8 kJ / mol. It can be seen from the combustion equation that the amount of magnesium and magnesium oxide is the same. Let us find this number n = 1000 / 601.8 = 1.662 mol. We find the mass of magnesium m (Mg) = 1.662 * 24.305 = 40.4 g.

Answer: You need to burn 40.4 g of magnesium.