CHEMISTRY HOMEWORK

Question

A researcher studying the nutritional value of a new candy places a  sample of the candy inside a bomb calorimeter and combusts it in excess oxygen. The observed temperature increase is  If the heat capacity of the calorimeter is  how many nutritional Calories are there per gram of the candy?

Answer 1

A researcher studying the nutritional value of a new candy places a 3.90 g sample of the candy inside a bomb calorimeter and combusts it in excess oxygen. The observed temperature increase is 2.94 ∘C. If the heat capacity of the calorimeter is 36.20 kJ⋅K−1, how many nutritional Calories are there per gram of the candy?

q = C∆T

q = heat = ?

m = mass = 3.90 g

C = heat capacity = 36.20 kJ/º

∆T = change in temperature = 2.94º (note: change in temp of 1ºC is same as 1ºK so temperature scale is not relevant here)

q = (36.20 J/º)(2.94º) = 106 kJ

Since there were 3.90 g of candy, the kJ per gram = 106 kJ/3.90 g = 27.3 kJ/g

To convert to Calories per gram, we use the conversion factor of 1 Cal = 4.184 kJ/Cal

27.3 kJ/g x 1 Cal/4.184 kJ = 6.52 Cal/gram