Question

The heats of combustion of rhombic and monoclinic sulphur are $-70960$ and $-71030$ calorie respectively. What will be the heat of conversion of rhombic sulphur to monoclinic sulphur?

• A. $-70960cal$
• B. $-71030cal$
• C. $+70cal$
• D. $-70cal$

Answer 1

Answer: (C)

$+70cal$

The conversion reaction of rhombic sulphur to monoclinic sulphur is given by,

$S_{rhombic}\to S_{monoclinic}$

Hence, $\Delta H_{conversion}=\Delta H_{\text{combustion of S(rhombic)}}-\Delta H_{\text{combustion of S(monoclinic)}}$

$\Delta H_{conversion}=\left[\right(-70960)-(-71030\left)\right]=70cal.$

$\therefore$ answer is option $C$.