Question

To determine the calories of a food, the energy released is calculated based on the mass used in the calorimeter. If a 0.8 g nut is consumed in a bomb calorimeter and the resultant temperature change is 80.3 degrees C for 50 mL of water, what would be the energy in Calories per gram of nut? One joule = 2.39 x 10^-4 Calories.

If supposed to use qsoln = CxmxDt, C = 4.18J/gdegreesC.

qsoln = (4.18)(50)(80.3) = 16782.7J
qrxn = -16782.7 J
I know you get DHrxn from qrxn/moles, but do I need to find the moles? If so, how do I figure this out with the information given? Am I doing this problem wrong? If so, please explain.

Answer 1

Convert 16782.7 J to Calories and that will be calories per 0.8 gram. (Note: you may want to look at the number of significant figures if your prof is picky about that.) So this will give you calories/gram of nut and that's what the problem asks for.