Question

When 0.100 g of calcium oxide is added to 125 g of water at 23.6°C in a coffee cup calorimeter, this reaction occurs:

CaO (s) + H2O(l) -> Ca(OH)2 (aq)
∆H = -81.9kJ/mol

If the specific heat capacity of water is 4.184 J g-1 °C-1, what is the final temperature of the solution?

Answer 1

figure the moles of CaO in 100 g. Multiply that by -81.8 kJ/mol. Notice the negative sign, that means heat is not absorbed.

that is the heat given off.
notice the amount of CaO is trivial compared to the water, so assume all of the Water does not react, and there is 100g of water being heated.

finally, the sum of heats ABSORBED is zero...
100*cwater*(Tf-23.6)+heatabove=0
solve for Tf