In a coffee-cup calorimeter, 1.20 g of NH4NO3 is mixed with 76.0 g of?

Question

In a coffee-cup calorimeter, 1.20 g of NH4NO3 is mixed with 76.0 g of water at an initial temperature of 25.00°C. After dissolution of the salt, the final temperature of the calorimeter contents is 23.21°C. Assuming the solution has a heat capacity of 4.18 J/°C·g and assuming no heat loss to the calorimeter, calculate the enthalpy change for the dissolution of NH4NO3 in units of kJ/mol.

Answer 1

The molar mass of NH4NO3 is 80.04336 g/mol.
(4.18 J/°C·g)*(76.0g + 1.20g)*(25.00°C-23.21°C)*(80.04336 g/mol)/(1.20 g)
= 38.5 kJ/mol
38.5 kJ/mol is the enthalpy change for the dissolution of NH4NO3.