When 3.00 g of KCl dissolves in 200.0 g of water contained in an insulated cup, the temperature of the water decreases from 25.00 °C to 21.75 °C. Assuming the specific heat capacity of the solution is 4.18 J g⁻¹ °C⁻¹ and the density is 1.00 g mL⁻¹, what is the molar enthalpy change, ΔH, for the dissolution of KCl(s)? (Molar mass of KCl = 74.55 g mol⁻¹)
a) +6.76kJ mol−1
b) −67.6kJ mol−1
c) +67.6kJ mol−1
d) +33.8kJ mol−1