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

-24.76 kJ/mol

Step-by-step 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 * 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 =
`(-3.405)/(0.1375)`

Energy density = -24.76 kJ/mol

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