Compound A is added into a calorimeter that contains 0.750 litres of water. If the dissolution of 5.0 g of this compound causes the temperature of the water to rise to 45.0 °C, what is the enthalpy of solution of compound A?
q = mass H2O x specific heat H2O x 9Tfinal-Tinitial).
q/gram A = q/5.0g.
If you want it in J/mol, then
(q/5.0) x molar mass A.