In a constant pressure calorimeter, 135 mL of a 1.00 M alkaline earth metal (Me) chloride solution were?

Question

added to 135 mL of a 1.00 M potassium sulphate solution. The total heat capacity of the calorimeter including all the contents was 1.75 kJ oC-1. The temperature in the calorimeter rose from 24.50oC to 28.70 oC.

Calculate the enthalpy change, in kJ, for the reaction:
Me2+ (aq) + SO42- (aq) = MeSO4 (s).
Me is the alkaline earth metal in question.

Answer 1

135 mL of 1.00 M MeCl2 = 0.135 mol MeCl2
135 mL of 1.00 M K2SO4 = 0.135 mol K2SO4
So the chemicals may fully react to form 0.135 mol MeSO4:
Me(2+)(aq) + SO4(2-)(aq) = MeSO4 (s).

Heat generated = (28.70°C - 24.50°C)*1.75kJ/°C = 7.35 kJ.
Hence the enthalpy change = 7.35 kJ/0.135 mol = 54.4 kJ/mol.