Question

Pure solid sulphur absorbs $2.7\text{kcal}$ of heat and becomes molten sulphur of mass $300\text{g}$. What is the specific latent heat of melting of sulphur in ${\text{J g}}^{-1}$?

• A. 37.8

Answer 1

The correct option is A 37.8
Given:
Mass of the solid/molten sulphur, ${\text{m}}_{\text{S}}=300\text{g}$
Heat required to melt the sulphur, $\text{Q}=2.7\text{kcal}$
Specific latent heat of melting of sulphur is the amount of heat required to melt a unit mass of sulphur = ${\text{L}}_{\text{S}}=\frac{\text{Q}}{{\text{m}}_{\text{s}}}=\frac{2.7\times {10}^3}{300}=9{\text{cal g}}^{-1}$

$1{\text{cal g}}^{-1}=4.2{\text{J g}}^{-1}$

$⟹9{\text{cal g}}^{-1}=9\times 4.2{\text{J g}}^{-1}$

$⟹{\text{L}}_{\text{S}}=37.8{\text{J g}}^{-1}$