Question

5 g sulphur is present in 100 g of $C{S}_2.\Delta T_b$ of solution 0.954 and $K_b$ is 4.88. The molecular formula of sulphur is

• A. $S_2$
• B. $S_4$
• C. $S_3$
• D. $S_8$

Answer 1

Answer: (D)

$\Delta T_b=K_b\times m$

$m=\frac{\Delta T_b}{K_b}$

or $\frac{W_2\times 1000}{M_2\times W_1}=\frac{\Delta T_b}{K_b}$

or $\frac{5\times 1000}{M_2\times 100}=\frac{0.954}{4.88}$

$M_2=256$

Atomic weight of sulphur = 32

Number of sulphur atom $=\frac{Molecular\text{weight}}{Atomic\text{weight}}=\frac{256}{32}=8$

Hence Molecular formula $=S_8$ .