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?
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.

Answer 1

1384 kJ/mol

Step-by-step 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