How do you calculate the standard enthalpy of combustion of diamonds?

Question

How do you calculate if the Enthalpy of formation is 1.895?

How do you calculate if the Enthalpy of formation is +1.895?

is it +1.895 or -1.895 for combustion?

Answer 1

i think combustion standard enthalpy is calculated the same as any reaction. if its just standard H u want then its just products - reactants at standard.

in this case, if you say diamonds H0 is 1.895 then:
1.895 - 0 (graphite is just carbon in its standard state, right?) = 1.895

this makes sense since diamonds are highly organized so change in entropy will be very very small meaning with gibs free energy formula
G = H - TS (delta g, h, s)
then in order for G to equal 0, H must = TS...S being very small. T would equal 1.895/very very small S = very high temperature T. and we all know diamonds are only formed under very high temperature and pressures. hope that helps =P

Answer 2

Weee! Diamonds are shiny!