Q12 / 200 · Manipal (MET) 2012 · Chemistry

$\begin{aligned} \mathrm{S}_{\text {(rhombic) }}+\mathrm{O}_2(\mathrm{~g}) \longrightarrow \mathrm{SO}_2(\mathrm{~g}), \\ \Delta H=-297.5 \mathrm{~kJ} \\ \mathrm{~S}_{\text {(monoclinic) }}+\mathrm{O}_2(\mathrm{~g}) \longrightarrow \mathrm{SO}_2(\mathrm{~g}), \\ \Delta H=-300 \mathrm{~kJ} \end{aligned}$ The data can predict that

  • A
    rhombic sulphur is yellow in colour
  • B
    monoclinic sulphur has metallic lusture
  • C
    monoclinic sulphur is more stable
  • Correct answer
    D
    $\Delta H_{\text {transition }}$ of $\mathrm{S}_R$ to $\mathrm{S}_M$ is endothermic

Solution

Substracting equation (II) from (I), we get $\mathrm{S}_R \longrightarrow \mathrm{~S}_M, \quad \Delta H=+2.5 \mathrm{~kJ}$ Thus, $\mathrm{S}_R$ to $\mathrm{S}_M$ transition is an endothermic reaction.

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

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