(a) In an exothermic reaction the enthalpy of product is less than that of the reactants
(b) ΔHfus=ΔHsubl−ΔHvap
(c) A reaction for which ΔH∘ < 0 and ΔS > 0 is possible at all temperatures.
(d) ΔH is less than ΔE for combustion of carbon to carbon dioxide.