Question

A researcher studying the nutritional value of a new candy places a 4.90-gram sample of the candy inside a bomb calorimeter and combusts it in excess oxygen. The observed temperature increase is 2.97 °C. If the heat capacity of the calorimeter is 46.00 kJ·K–1, how many nutritional Calories are there per gram of the candy?

Answer 1

Heat evolved = heat capacity x temp rise

Heat evolved = 46.00 kJ.k^-1 x 2.97 K

Heat evolved = 136.62 kJ

Then, find energy per gram of candy. To get in KJ per gram divide the heat evolved by sample

136.62 KJ / 4.90 g = 27.88 KJ/g

Convert to Calories (kilocalories):

1 KJ = 0.239 Kcal

27.88 KJ = 27.88 x 0.239 = 6.66 Kcal

Or 27.88 KJ/g = 6.66 Kcal/g

So , there are 6.66 kcal burned per gram of candy.