Question

Given
(I) `C`(diamond) `+O_(2)(g)rarrCO_(2)(g),DeltaH^(@)=-92.0Kcal mol^(-1)`
(II) `C`(graphite) + `O_(2)(g)rarrCO_(2)(g),DeltaH^(@)=-96.0Kcal mol^(-1)`
A. `2.907KcalK^(-1)`
B. `2.013KcalK^(-1)`
C. `305.4calK^(-1)`
D. `-2.013KcalK^(-1)`

Answer 1

Correct Answer - A
Eq . `(I)` and Eq . `(II)` give
C(diamond)`rarr`(graphite)
`DeltaH^(@)=-02-(-96)=+4.0Kcal mol^(-1)`
Moles of diamond `=(2.6xx1000g)/(12gmol^(-1))=216.6mol`
`DeltaH^(@)` (to convert `200mol` of diamond into graphite)
`=216.6xx4.0Kcal=866.4Kcal`
`:. DeltaS=(DeltaH^(@))/(T)=(866.4Kcal)/(298K)=2.907KcalK^(-1)`