Question

When 0.1375 g of solid magnesium is burned in a constant-volume bomb calorimeter, the temperature increases by 1.126°C. The heat capacity of the bomb calorimeter, determined in a separate experiment, is 3024 J/°C. Calculate the heat given off by the burning magnesium in kJ/mol.

Answer 1

Answer:

-24.76 kJ/mol

Explanation:

given,

mass of solid magnesium burned = 0.1375 g

the temperature increases by(ΔT) 1.126°C

heat capacity of of bomb calorimeter (C_{cal})= 3024 J/°C

heat absorbed by the calorimeter

    $q_{cal} = C_{cal}\DeltaT$

    $q_{cal} = 3024 \times 1.126$

    $q_{cal} =3405.24\ J$

    $q_{cal} =3.405\ kJ$

heat released by the reaction

    $q_{rxn} = -q_{cal}$

    $q_{rxn} = -3.405\ kJ$

energy density will be equal to heat released by the reaction divided by the mass of magnesium

Energy density = $\dfrac{-3.405}{0.1375}$

Energy density = -24.76 kJ/mol

heat given off by burning magnesium is equal to -24.76 kJ/mol