Question

The equivalent weight of crystalline Oxalic acid is

Answer 1

Step 1: Equivalent mass:

• The equivalent mass of an acid is defined as the molecular mass of an acid divided by the basicity of the acid.

Step 2: Formula for equivalent mass:

$\mathrm{Equivalent}\mathrm{mass}\mathrm{of}\mathrm{acid}=\frac{\mathrm{Molar}\mathrm{mass}\mathrm{of}\mathrm{acid}}{\mathrm{Basicity}\mathrm{of}\mathrm{acid}}$

Step 3: Calculation for equivalent mass:

• The crystalline oxalic acid has a chemical formula ${\left(\mathrm{COOH}\right)}_2.2{\mathrm{H}}_2\mathrm{O}$.
• The molar mass of crystalline oxalic acid is $126\mathrm{g}{\mathrm{mol}}^{-1}$.

$$\begin{gathered} \mathrm{Molecular}\mathrm{mass}\mathrm{of}\mathrm{oxalic}\mathrm{acid}=\mathrm{Atomic}\mathrm{mas}\mathrm{of}\mathrm{C}+\mathrm{Atomic}\mathrm{mass}\mathrm{of}\mathrm{O}+\mathrm{Atomic}\mathrm{mass}\mathrm{of}\mathrm{H} \\ \mathrm{Molecular}\mathrm{mass}\mathrm{of}\mathrm{oxalic}\mathrm{acid}=(2\times 12)+(6\times 16)+(6\times 1) \\ \mathrm{Molecular}\mathrm{mass}\mathrm{of}\mathrm{oxalic}\mathrm{acid}=126\mathrm{g}{\mathrm{mol}}^{-1} \end{gathered}$$

• The basicity of oxalic acid is $2$. Since 1 mole of oxalic acid can release 2 moles of ${\mathrm{H}}^{+}$ ions and neutralize 2 moles of ${\mathrm{OH}}^{–}$ ions, the number of equivalent moles here is equal to 2.

$$\begin{gathered} \mathrm{Equivalent}\mathrm{mass}\mathrm{of}\mathrm{crystalline}\mathrm{oxalic}\mathrm{acid}=\frac{\mathrm{Molar}\mathrm{mass}\mathrm{of}\mathrm{crystalline}\mathrm{oxalic}\mathrm{acid}}{\mathrm{Basicity}\mathrm{of}\mathrm{crystalline}\mathrm{oxalic}\mathrm{acid}} \\ \mathrm{Equivalent}\mathrm{mass}\mathrm{of}\mathrm{crystalline}\mathrm{oxalic}\mathrm{acid}=\frac{126\mathrm{g}{\mathrm{mol}}^{-1}}{2}=63\mathrm{g}{\mathrm{eq}}^{-1} \end{gathered}$$

Thus, the equivalent mass of crystalline oxalic acid is $63\mathrm{g}{\mathrm{eq}}^{-1}$.