Question

$S$ (rhombic) $+ O _{2}( g ) \rightarrow SO _{2}( g ) ; \Delta H =-297.5\, kJ$
$S$ (monoclinic) $+ O _{2}( g ) \rightarrow SO _{2}( g ) ; \Delta H =-300\, kJ$
The above data can predict that

• A. Rhombic sulphur is yellow in colour,
• B. Monoclinic sulphur has metallic lustre
• C. Monoclinic sulphur is more stable
• D. $\Delta H _{\text {(Transition) }}$ of $S ( R )$ to $S ( M )$ is endothermic process

Answer 1

Answer: (D)

$ S _{( rhombic )}+ O _{2}( g ) \longrightarrow SO _{2}( g )$;
$\Delta H =-297.5 \,kJ $ ... (1)
$ S _{(\text {monoclinic })}+ O _{2}( g ) \longrightarrow SO _{2}( g ) $;
$\Delta H =-300\, kJ$ ... (2)
Subtracting (2) from (1),
$S _{(\text {rhombic })} \longrightarrow S _{(\text {monoclinic })}$;
$ \Delta H =(-297.5+300) kJ =+2.5\, kJ$
$\Rightarrow $ This transition is endothermic.