The student places 191.95 g of water at 25°C into a coffee-cup calorimeter and immerses a thermometer in the water. After 50 s, the student adds 5.123 g of solid urea, also at 25°C, to the water and measures the temperature of the solution as the urea dissolves. A plot of the temperature data is shown in the graph. (a) Determine the change in temperature of the solution that results from the dissolution of the urea.

(b) According to the data, is the dissolution of urea in water an endothermic process of an exothermic process? Justify your answer.

(c) Assume that the specific heat capacity of the calorimeter is negligible and that the specific heat capacity of the solution of urea and water is 4.2 J/g°C throughout the experiment.

(i) Calculate the heat of dissolution of the urea in joules.

(ii) Calculate the molar enthalpy of solution of urea in kJ/mol

(d) The student repeats the experiment and this time obtains a result for enthalpy of solution of urea that is 25% above the accepted value of 8.5 kJ/mol. Calculate the value of enthalpy of solution that the student obtained in this second trial.

(e) The student performs a third trial of the experiment but this time adds urea that has been taken directly from a refrigerator at 5°C. What effect, if any, would use the cold urea instead of urea at 25°C have on the experimentally obtained value of enthalpy of the solution? Justify your answer.