Question

Equivalent weight of crystalline oxalic acid is:
A) 90
B) 63
C) 53
D) 45

Answer 1

Hint: For the calculation of equivalent Weight, divide the molecular weight with the n-factor of the molecule. n-factor is defined as the number of ${{\text{H}}^{+}}$ ions replaced by 1 mol of acid in a reaction and number of $\text{O}{{\text{H}}^{-}}$replaced by 1 mol of base in a reaction.

Complete step by step:
Hydrated Oxalic Acid is a white crystalline organic compound. Oxalic acid acts as a reducing agent for metal oxides to remove tarnish as well as rust or ink stains. It is used commercially as a laundry rinse, wood-bleaching agent, and calcium remover. Oxalic acid can remove some paints and varnishes. It is also used as a mordant in dyeing textiles and in the manufacture of ink.
The formula of oxalic acid is $\text{(}{{\text{C}}_{2}}{{\text{H}}_{2}}{{\text{O}}_{4}})$. Its usual form is that of the crystalline hydrate.
It is represented by the formula \[{{\text{(COOH)}}_{2}}\text{.2}{{\text{H}}_{2}}\text{O}\]
The formula of hydrated oxalic acid is${{\text{H}}_{2}}{{\text{C}}_{2}}{{\text{O}}_{4}}.2{{\text{H}}_{2}}\text{O}$. Therefore, the equivalent weight of the acid is molecular weight (126 g/mol) divided by n-factor (valency=2). Therefore, we should divide 126 by 2. Thus, the equivalent weight of oxalic acid is 63.
Mathematically, we can describe the formula as-
The Formula of the Equivalent Weight is given by
Equivalent Weight = Molecular Weight/ No. of Equivalent Moles
The Oxalic Acid\[{{\text{(COOH)}}_{2}}\text{.2}{{\text{H}}_{2}}\text{O}\]has two moles of acidic \[{{\text{H}}^{+}}\] that means one mole of oxalic acid can neutralize 2 moles of \[\text{O}{{\text{H}}^{-}}\].
Therefore, the no. of equivalent moles = 2
It is also called an n-factor.
Equivalent Weight =Molecular Weight/ No. of Equivalent Moles
\[=\frac{126}{2}=63\text{g/eq mol}\]
Therefore, the equivalent weight of hydrated oxalic acid\[=63\text{g/eq mol}\]

Hence, we can conclude that the correct option is (b) 63.

Note: Different acid has different no. of equivalent moles. For example: HCl has 1 equivalent mole whereas \[{{\text{H}}_{2}}\text{S}{{\text{O}}_{4}}\] has 2 equivalent moles.