Consider the following data.

2 CaO(s) 2 Ca(s) + O2(g)		H = +1270.2 kJ
C(s) + O2(g) CO2(g)		H = -393.5 kJ
CaCO3(s) CaO(s) + CO2(g)		H = +178.3 kJ

Use Hess's law to calculate H for the reaction below.

2 CaCO₃(s) 2 C(s) + 2 Ca(s) + 3 O₂(g)

H = kJ

(THE ANSWER IS NOT -311.0)