Question

part 1
When 0.633 g of Ca metal is added to 200.0 mL of 0.500 M HCl(aq), a temperature increase of 103C is observed.
Assume the solution's final volume is 200.0 mL, the density is 1.00 g/mL, and the heat capacity is 4.184 J/gC.
(Note: Pay attention to significant figures. Do not round until the final answer.)
The molar heat of reaction, H rxn, for the reaction of

Ca(s) + 2H+(aq) Ca2+(aq) + H2(g)

is kJ/mol.

part 2
When 0.911 g of CaO is added to 200.0 mL of 0.500 M HCl(aq), a temperature increase of 374C is observed.
Assume the solution's final volume is 200.0 mL, the density is 1.00 g/mL, and the heat capacity is 4.184 J/gC.
(Note: Pay attention to significant figures. Do not round until the final answer.)
Hrxn, for the reaction of

CaO(s) + 2H+(aq) Ca2+(aq) + H2O(l)

is kJ/mol.

part 3
Based on the results of problems 8 and 9 if the heat of formation of water is -286 kJ/mol,

The H ffor CaO(s) is

Answer 1

how do you do part 3?

i tried solving it multiple times...