The heat released by the reaction is absorbed by the solution, resulting in the temperature change.
Mass of solution = density x volume
Mass = 500 x 1 = 500 grams
Heat absorbed:
Q = mCpΔT
Q = 500 x 4.186 x (24.21 - 23.4)
Q = 1,695 J
Moles of silver nitrate = molarity x volume in L
Moles of silver nitrate = 0.1 x 0.5
Moles of silver nitrate = 0.05
Heat of reaction = 1,695 / 0.05
Heat of reaction = 33.9 kJ/mol