Question

A 0.1375-gram sample of solid magnesium is burned in a constant-volume bomb calorimeter that has a heat capacity of 3024 J/⁰C . The temperature increases by 1.126 ⁰C. Calculate the heat given off by the burning of Mg, in kJ/g and in kJ/mol. (Atomic Mass of Mg = 24.31 g/mol)

Answer 1

$Q$ _cal $= C$_cal$\Delta T$

$=3024 \times 1.126$

$=3405J$

then heat of reaction of magnesium solid in $kj/j$

$Q$_rn $= \frac{(3405\times .1375)}{1000}$

$= -24.76kj/g$

so that amount of heat liberated in reaction is $= -24.76kj/g$

$Q$rn $= -\frac{24.76kj}{gMg} \times \frac{24.31gMg}{1MOL Mg}$

$= - 601.9 kj/mol$

so that amount of heat liberated in reaction is$= - 601.9 kj/mol$