Standard molar enthalpy of SrCO3?

Question

Given the following data:

SrO (s) + CO2 (g) --> SrCO3 (s) delta H= -234 kJ

2 Sr (s) + O2 (g) --> 2 SrO (s) delta H= -1184kJ

C (graphite) + O2 (g) --> CO2 (g) delta H= = -394

Calculate the standard molar enthalpy of formation for SrCO3 (s).

Answer 1

delta H for the reaction is the sum of all of the steps needed to get to the endpoint, namely the reactions you've listed

delta H =-1812 kJ/mol

Answer 2

The first one, plus half the second one, plus the third one!

Add them all up in the quantities that I have stated.