Question

The equivalent weight of bivalent metal is $32.7\mathrm{g}{\mathrm{eq}}^{-1}$. What is the molecular weight of its chloride?

Answer 1

Step 1: Equivalent Weight:

• Equivalent weight is equal to the molecular/atomic weight divided by the number of electrons involved in the reaction per molecule/atom/ion.
• It is expressed as:

$\mathrm{Equivalent}\mathrm{weight}=\frac{\mathrm{Molecular}\mathrm{weight}}{\mathrm{Valency}}$

Step 2: Given Information:

• The equivalent weight of bivalent metal is $32.7\mathrm{g}{\mathrm{eq}}^{-1}$.

Step 3: Calculation for molecular weight:

$$\begin{gathered} \mathrm{Atomic}\mathrm{weight}\mathrm{of}\mathrm{bivalent}\mathrm{metal}=\mathrm{equivalent}\mathrm{weight}\times \mathrm{valency} \\ \mathrm{Atomic}\mathrm{weight}\mathrm{of}\mathrm{bivalent}\mathrm{metal}=32.7\times 2=65.4\mathrm{g} \end{gathered}$$.

• The formula for chloride of bivalent metal = ${\mathrm{MCl}}_2$
• Atomic weight for $\mathrm{Cl}=35.5$

So, $\mathrm{Molecular}\mathrm{weight}=65.4+2(35.5)$

$\mathrm{Molecular}\mathrm{weight}=136.4\mathrm{g}$

Thus, the molecular weight of the bivalent metal i.e. ${\mathrm{MCl}}_2$ is $136.4\mathrm{g}$.