Question

A metal oxide contains $20\%$ oxygen by weight. Find the equivalent weight.

Answer 1

Step 1: Equivalent mass:

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

$\mathrm{Equivalent}\mathrm{weight}=\frac{\mathrm{Atomic}\mathrm{weight}}{\mathrm{Valency}}$…………………..(i)

Step 2: Given Information:

• A metal oxide contains $20\%$ oxygen by weight i.e. $20\mathrm{g}$
• Thus, there is $80\%$ metal by weight i.e. there is $80\mathrm{g}$ metal in the metal oxide.

Step 3: Formula used for the calculation of the equivalent weight of the metal:

$\mathrm{Equivalent}\mathrm{weight}\mathrm{of}\mathrm{metal}=\frac{\mathrm{mass}\mathrm{of}\mathrm{metal}}{\mathrm{mass}\mathrm{of}\mathrm{oxygen}}\times \mathrm{equivalent}\mathrm{weight}\mathrm{of}\mathrm{oxygen}$

Step 4: Calculation for an equivalent weight of metal:

Using (i), The equivalent weight of oxygen is $\frac{16}{2}=8$

$$\begin{gathered} \mathrm{Equivalent}\mathrm{weight}\mathrm{of}\mathrm{metal}=\frac{80}{20}\times 8 \\ \mathrm{Equivalent}\mathrm{weight}\mathrm{of}\mathrm{metal}=32 \end{gathered}$$

Thus, the equivalent weight of metal is 32.