Question

Inside a calorimeter, two solutions are mixed and result in an endothermic reaction. Which of the following best illustrates how this reaction affects the water in the calorimeter? (2 points)
Select one:
a. The reaction has no effect on the water. The kinetic energy of the water molecules remains the same.
b. The reaction causes the temperature of the water to increase. The kinetic energy of the water molecules increases.
c. The reaction causes the temperature of the water to decrease. The kinetic energy of the water molecules decreases.
d. The reaction causes the temperature of the water to decrease. Then, the water gains heat from the surroundings and the kinetic energy of the water molecules increases.

Answer 1

The correct option is C. A calorimeter is an isolated system. In isolated systems there is no exchange whatsoever with the surrounding. In an isolated system, an endothermic reaction results in a decrease in the temperature of the system. This is in contrast to the effect of an endothermic reaction in an open system. The heat of reaction remains a positive quantity.