A 0.1326 g sample of magnesium was burned in an oxygen bomb calorimeter. The total heat capacity of the calorimeter plus water was 5,760 J/^$\circ$C. If the temperature rise of the calorimeter with water was 0.570^$\circ$C, calculate the enthalpy of combustion of magnesium.Mg(s) + 1/2O₂(g) $\rarr$MgO(s) A) -3280 kJ/mol B) -602 kJ/mol C) -24.8 kJ/mol D) 106 kJ/mol E) 435 kJ/mol

Question

Quizplus · Accepted Answer

The enthalpy of combustion of magnesium can be calculated using the formula: $\Delta H = -q/n$, where $q$ is the heat absorbed by the calorimeter and $n$ is the number of moles of magnesium. First, calculate $q = C \times \Delta T = 5760 \, \text{J/}^\circ\text{C} \times 0.570 \, ^\circ\text{C} = 3283.2 \, \text{J}$. The number of moles of magnesium is $0.1326 \, \text{g} / 24.305 \, \text{g/mol} = 0.00545 \, \text{mol}$. Thus, $\Delta H = -3283.2 \, \text{J} / 0.00545 \, \text{mol} = -602,348 \, \text{J/mol} = -602 \, \text{kJ/mol}$.

A 01326 G Sample of Magnesium Was Burned in an Oxygen