Calculate the standard enthalpy of formation of ethanol..!! help?

1. if the standard enthalpy of combustion of ethanol (C2H5OH) (l) at 298 K is -1368 kJ*mol^-1, calculate the standard enthalpy of formation of ethanol. The standard enthalpies of formation of carbon dioxide and liquid water are -393.51 and -285.83 kJ*mol^-1, respectively, 1. −688.7 kJ · mol−1 2. −276.5 kJ ·... show more 1. if the standard enthalpy of combustion of ethanol (C2H5OH) (l) at 298 K is -1368 kJ*mol^-1, calculate the standard enthalpy of formation of ethanol. The standard enthalpies of formation of carbon dioxide and liquid water are -393.51 and -285.83 kJ*mol^-1, respectively,
1. −688.7 kJ · mol−1
2. −276.5 kJ · mol−1
3. +276.5 kJ · mol−1
4. +688.7 kJ · mol−1
5. −344.3 kJ · mol−1

2. Calculate the enthalpy change for the reaction:

2 SO2(g) + O2(g) → 2 SO3(g) .

∆Hf for SO2(g) = −16.9 kJ/mol, ∆Hf for SO3(g) = −21.9 kJ/mol.
Answer in units of kJ/mol.