# Question #b60b5

##### 1 Answer

Using the data given, the heat of combustion would be 308 kJ/mol.

To calculate the heat of combustion, you must determine the amount of heat energy released and divide by the number of moles of ethanol combusted.

Heat:

The heat of combustion is used to raise the temperature of 800 g of water from 23 C to 31 C, or a difference of 8 C. The heat capacity of water is 4.184 J/g/C, so the total heat energy released is

The molar mass of ethanol is 46.07 g/mol. Therefore, the mole of ethanol combusted is

Finally, the heat of combustion of ethanol is calculated to be

HOWEVER! The actual heat of combustion of ethanol is 1370.7 kJ/mol so the data given in the problem are not correct. Most likely, the person who made up the problem forgot to convert from kcal/mol to kJ/mol because the heat of combustion in these units is 328 kcal/mol.