Q17 / 160 · TS EAMCET 2022 (20 Jul Shift 1) · Chemistry

The correct order of " $\Delta_f \mathrm{H}^{\circ}$ " values of Diamond (I), Graphite (II) and Fullerene (III) is

  • A
    I > II > III
  • B
    II > I > III
  • Correct answer
    C
    III > I > II
  • D
    III > II > I

Solution

Heat of formation $\left(\Delta_{\mathrm{f}} \mathrm{H}^0\right)$ values of Graphite (II) is taken as zero since it is the most stable allotrope of carbon. $\Delta_{\mathrm{f}} \mathrm{H}^{\mathrm{O}}$ $($ Diamond $)=1.90 \mathrm{~kJ} / \mathrm{mol}$ and $\Delta_{\mathrm{f}} \mathrm{H}^{\mathrm{o}}($ Fullerene $)=38.1 \mathrm{~kJ} / \mathrm{mol}$. The correct order : (III) $>$ (I) $>$ (II)

Hence, the correct answer is option: 'C'.

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