Question

A calorimeter contains 280.0g of water at 13.5C. When 0.250g of a substance with a molar mass of 510.0g/mol is dissolved, the temperature of the resultant solution increases to 17.5C. Assume that the specific heat and density of the resulting solution are equal to those of water, 4.18J/gC and 1.00 g/mL, respectively and assume that no heat is lost to the calorimeter itself, nor to the surroundings. Calculate the amount of heat in Joules released by dissolving the substance.

Answer 1

The change in heat is simply equal to:

change in heat ΔH = final enthalpy – initial enthalpy

ΔH = [280.25 g * 4.18J/gC * (17.5°C)] – [280 g * 4.18J/gC * 13.5°C]

ΔH = 4,699.89 J = 4.7 kJ

Hence heat released is about 4.7 kJ