Question

Consider the isomerization equlibria of an alkene (C4H8) that co-exists as three isomers.

Reaction 1: cis-2-butene ⇔ trans-2-butene
Reaction 2: cis-2-butene ⇔ 2-methylpropene
Reaction 3: trans-2-butene ⇔ 2-methylpropene

Known values at 300k are:
cis-2-butene: standard G of formation = 66kJ/mol
Standard enthalpy of formation = -7.0kJ/mol

trans-2-butene: standard G of formation = 63kJ/mol
Standard enthalpy of formation = -11.2kJ/mol

2-methylpropene: standard G of formation =58.0kJ/mol
Standard enthalpy of formation = not known

The temperature of the above system is raised to 400K and equilibrium is re-established. The mole percentage of trans-2-butene at the new equilibrium is determined to be 18%. Calculate the enthalpy of formation and the entropy of formation for reactions 2 and 3