There are two chlorides of sulphur S₂Cl₂ and SCl₂. What is the equivalent mass of S in SCl₂

The correct option is 16 g/mole.

To understand why this is the correct answer, let us break down the concept of equivalent mass and perform the calculation step-by-step.

1. Definition of Equivalent Mass of an Element:
The equivalent mass of an element is defined as the mass of the element that combines with or displaces a standard mass of another element. By convention, the standard reference values are:
- 1.008 parts by mass of hydrogen,
- 8 parts by mass of oxygen, or
- 35.5 parts by mass of chlorine.

Therefore, the equivalent mass of sulphur (S) in a chloride is the mass of sulphur that combines with 35.5 g of chlorine (Cl).

2. Analyzing the Compound ${\mathrm{SCl}}_2$:
In sulfur dichloride (${\mathrm{SCl}}_2$):
- There is 1 atom of sulphur (S) combined with 2 atoms of chlorine (Cl).
- The atomic mass of Sulphur (S) = 32 g/mole.
- The atomic mass of Chlorine (Cl) = 35.5 g/mole.

3. Calculating the Combining Masses:
The mass of chlorine in 1 mole of ${\mathrm{SCl}}_2$ is:
$2\times 35.5\text{g}=71\text{g}$

This means that 32 g of sulphur combines with 71 g of chlorine in ${\mathrm{SCl}}_2$.

4. Determining the Equivalent Mass of Sulphur (S):
Using the definition of equivalent mass (the mass combining with 35.5 g of chlorine):
$\text{Equivalent mass of S}=\frac{\text{Mass of Sulphur}}{\text{Mass of Chlorine}}\times 35.5$

Substituting the values:
$\text{Equivalent mass of S}=\frac{32}{71}\times 35.5$

Since $\frac{35.5}{71}=\frac{1}{2}$:
$\text{Equivalent mass of S}=32\times \frac{1}{2}=16\text{g/mole}$

Thus, the equivalent mass of sulphur in ${\mathrm{SCl}}_2$ is 16 g/mole.