1.A researcher studying the nutritional value of a new candy places a 5.10-gram
ID: 907535 • Letter: 1
Question
1.A researcher studying the nutritional value of a new candy places a 5.10-gram sample of the candy inside a bomb calorimeter and combusts it in excess oxygen. The observed temperature increase is 2.73 °C. If the heat capacity of the calorimeter is 38.40 kJ·K–1, how many nutritional Calories are there per gram of the candy?
2.When a 1.063-g sample of a new organic material was combusted in a bomb calorimeter, the temperature of the calorimeter (and its contents) increased from 23.29 °C to 29.62 °C. If the heat capacity (calorimeter constant) of the calorimeter is 32.67 kJ/°C, what is the heat of combustion per gram of the material?
Explanation / Answer
1.
mass of sample = 5.1 grams
DT = 2.73 C
Cp = heatcapacity of calorimeter = 38.40 kJ·K–1
heat released (q) = 38.4*2.73 = 104.832 kj
no of nutritional calories per gram = 104.832/5.1 = 20.55 kj/g
DH = -20.55 kj/gram = - 4.92 kcal/gram
2.
heat released (q) = Cp*DT
= 32.67*(29.62-23.29)
= 206.801 kj
heat of combustion per gram = 206.801/1.063 = 194.54 kj
DH = -194.54 kj/gram
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