Question

Which is expected to have the most negative standard enthalpy of formation? Which is expected to have the most negative standard enthalpy of formation?

i)H2O(l)

ii)N2(g)

iii)C4H8(g)

iv)HF(g)

Answer 1

negative enthalpies of formation --> exothermic reactions

possitive enthalpies of formation --> endothermic reactions

a)

H2O... H2(g) + O2() --> H2O very exothermic...

N2 --> expected to be 0...

C4H8 ---> C(s) + H2(g) --> this will form a double bond... so there is plenty of energy at the end.... this will be very possitive

H2(g) + F2(g) --> HF(g) --> this will be very exothermic... more than H2O...

choose

HF as higher, lower choose C4H8