Question

In a coffee-cup calorimeter, 1.91 g of NH4NO3 is mixed with 75.0 g of water at an initial temperature of 25.00oC. After the solution of the salt, the final temperature was 20.94oC. Assuming the solution has a heat capacity of 4.18 J/(goC) 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 soln = mass H2O x specific heat H2O x (Tfinal-Tinitial). This give you q for 1.91g NH4NO3.
(q/1.91g) x molar mass NH4NO3 gives you J/mol, then convert to kJ/mol.
Plug in the numbers to obtain q

Answer 2

52.9kj/mole