Question

When a 6.50g sample of solid sodium hydroxide dissolves in 100.0g of water in a coffee-cup calorimeter, the temperature rises from 21.6 Celsius to 37.8 Celsius. Calculate delta H (in kJ/mol NaOH) Assume that the specific heat of the solution is the same as that of pure water which is 4.184J/g-k. The answer is -44.4kJ/mol NaOH. I tried using Q = m*Cs*delta T however i realized that was a waste of time :(