`C_("graphite")+O_(2)(g)rarrCO_(2)(g)`
`deltaH=-94.05Kcalmol^(-1)`
`C_("diamond")+O_(2)(g),DeltaH=-94.50Kcalmol^(-1)
Therefore,

Options

A. `C_("graphite")rarrC_("diamond"),DeltaH_(298K^(@)=-450calmol^(-1)`
B. `C_("diamond")rarrC_("graphite"),DeltaH_(298K^(@)=+450calmol^(-1)`
C. Graphite is the stabler allotrope
D. Diamond is harder than graphite

Answer

D

Explanation

Heat energy is also involved when one allotropic from of an element is converted into another. Graphite is the stabler allotrope because the heat of transfomation of
`C_("diamond")rarrC_("graphite")` .
(i) `C_(("dia"))+O_(2)(g)=CO_(2)(g)DeltaH=-94.5Kcal`
(ii) `C_("graphite")+O_(2)(g)=CO_(2)(g)DeltaH=-94.0Kcal`
`DeltaH_("transformation")=-94.5-(-94.0)`
`=-0.5Kcal`