The molar heat of reaction, H rxn, for the reaction of

Question

Ca(s) + 2H+(aq) Ca2+(aq) + H2(g)
is -544.789 kJ/mol
and Hrxn, for the reaction of
CaO(s) + 2H+(aq) Ca2+(aq) + H2O(l)
is -192.42 kJ/mol,
the heat of formation of water is -286 kJ/mol,

The H ffor CaO(s) is _____ kJ/mol.

Thank you!

Answer 1

637.58

Answer 2

-637.58