Question

One tablespoon of peanut butter has a mass of 17.0 g. it is combusted in a calorimeter whose heat capacity is 110 kj/°c. the temperature of the calorimeter rises from 21.2 âc to 24.4 âc . what is the caloric content of peanut butter in cal/g?

Answer 1

If the calorimeter whose heat capacity is 110 kJ/°C rises its temperature from 21.2°C to 24.4°C, the heat transmited to it is: 110 kJ/°C * (24.4°C - 21.2°C) = 110kJ/°C (3.2°C) = 352 kJ.

That heat is generated by the combustion of 17.0 g of peanut butter, so the caloric content of it is: 352kJ / 17.0 g = 20.705 kJ/g.

Now use the conversion from kJ to cal:

1 cal = 4.184 J

=> 20.705kJ/g * 1000 J/kJ * 1cal/4.184J = 4948.6 cal/g

Answer: 4948.6 cal/g