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?

Pay attention to sign and significant figures!

If you wish to use scientific notation, use the "e" format:

e. g. 7.31e4 = 73100 or 1.90e-2 = 0.0190. Do not

enterunits.

1384 kJ/mol

Explanation:

The heat absorbed by the calorimeter is equal to the heat released due to the combustion of the organic compound. C is the total heat capacity of the calorimeter and Δt is the change in temperature from intial to final:

Q = CΔt = (3576 J°C⁻¹) (30.589°C - 25.000°C) = 19986.264 J

Extra significant figures are kept to avoid round-off errors.

We then calculate the moles of the organic compound:

(0.6654 g) (mol/46.07) = 0.0144432 mol

We then calculate the heat released per mole and convert to the proper units. (The conversion between kJ and J is infinitely precise and is not involved in the consideration of significant figures)

(19986.264 J) (1kJ/1000J) / (0.0144432 mol) = 1384 kJ/mol