Question

In a coffee-cup calorimeter, 1.50 g of NH4NO3 is mixed with 72.0 g of water at an initial temperature of 25.00°C. After dissolution of the salt, the final temperature of the calorimeter contents is 23.65°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

q extracted from the water is
q = mass H2O x specific heat H2O x (Tfinal-Tinitial)
That gives you q for 1.50g sample. The 1.5g sample is how many mols? That's 1.5/molar mass NH4NO3.
Then q from above/#mols = q in J/mol. Convert to kJ/mol.

Answer 2

59kg