Question

1. In two different experiments exactly 5 grams of fuel burns (combusts). The first experiment is under constant pressure conditions, and the second separate experiment is under constant volume conditions.

1. Which experiment is in a coffee cup calorimeter? And which is in a bomb calorimeter?
2. One experiment produces 25 kJ of heat and one experiment produces 23 kJ of heat. Which experiment (the constant pressure one or the constant volume one) produces 25 kJ of heat and which produces 23 kJ of heat? Why?
   
   Please type the answers, don't write them on a paper

Answer 1

(A) The coffee cup calorimeter is the experiment which is done under constant pressure. Since the system is open type which means system can expand and can change volume but the atmospheric pressure remains the same.

While the bomb calorimeter is the experiment which is done under constant volume. Since the system is closed type which means system can not expand but due to combustion amount of gases increases in the calorimeter the pressure they are facing will also increase.

(B) Since under constant pressure condition the system is expanding which means the system is performing work and will consume some amount of energy which is released to do the work. But on the other hand the system under constant volume conditions performs no such work and all the energy is released in form of heat.

Hence the enegy produced by the system under constant pressure will be less (I.e., 23kJ) than the system under constant volume (I.e., 25kJ)

In other words coffee calorimeter will produce 23 kJ of energy and bomb calorimeter will produce 25kJ of energy.