Identify the correct statement from the following.
I) Graphite is used as dry lubricant, as it possesses slippery nature.
II) Diamond is thermodynamically more stable than graphite.
III) Carbon black, coke, charcoal are impure forms of graphite or fullerenes.
IV)Diamond is measured in carats and one carat is 200 mg.

I. Graphite cleaves easily between the layers and, therefore, it is very soft and slippery. For this reason graphite is used as a dry lubricant in machines running at high temperature, where oil cannot be used as a lubricant.

II. Graphite is thermodynamically most stable allotrope of carbon and, therefore, ${∆}_{\mathrm{f}}{\mathrm{H}}^{⊝}$ of graphite is taken as zero. ${∆}_{\mathrm{f}}{\mathrm{H}}^{⊝}$ values of diamond and fullerene, C₆₀ are 1.90 and 38.1 kJ mol^–1, respectively.

III. Other forms of elemental carbon like carbon black, coke, and charcoal are all impure forms of graphite or fullerenes.

IV. Diamond is measured in carats (1 carat = 200 mg).

Hence, I, III, and IV are correct.