Question

In a constant

volume bomb calorimeter, the combustion of 0.6654 gof an organic
compound with a molecular mass of 46.07 amu causesthe temperature
in the calorimeter to rise from 25.000oC to 30.589
oC. The total heat capacity ofthe calorimeter and all
its contents is 3576 JoC-1. What is
the energy of combustion ofthe organic compound,
DU/ kJ
mol-1?

Answer 1

1383.34 kJ/mol is the energy released on combustion of the organic compound.

Step-by-step explanation:

Mass of an organic compound = 0.6654 g

Molar mass of organic compound = 46.07 g/mol

Moles of an organic compound =
`(0.6654 g)/(46.07 g/mol)=0.01444 mol`

Let heat evolved during burning of 0.6654 grams of an organic compound be -Q.

Heat absorbed by calorimeter = Q' = -Q

The total heat capacity of the calorimeter all its contents = C

C = 3576 J/°C

Change in temperature of the calorimeter =

ΔT = 30.589°C - 25.000°C = 5.589°C

`Q'=C* \Delta T`

`Q'=3576 J/^oC* 5.589^oC=19,975.536 J=19.975 kJ`

Q' = 19.975 kJ

Q = -19.975 kJ (negative sign; energy released)

0.01444 moles of an organic compound gives 19.975 kilo Joule.

The 1 mole of an organic compound will give :
`\Delta H_(comb)`

`\Delta H_(comb)=(-19.975 kilo Joule)/(0.01444 mol)`

`=-1383.34 kJ/mol`