Question

Equivalent weight of oxalic acid salt in the following reaction is (Atomic masses: O = 16, C =12, K= 19)
${{H}_{2}}{{C}_{2}}{{O}_{4}}+Ca{{(OH)}_{2}}\to Ca{{C}_{2}}{{O}_{4}}+{{H}_{2}}O$
A. 90
B. 45
C. 64
D. 128

Answer 1

Hint: Equivalent weight of a chemical can be calculated by identifying the number of hydrogens replaceable in the given chemical. The formula to calculate the equivalent of a chemical is as follows.
\[\text{Equivalent weight = }\dfrac{\text{Molecular weight of the chemical}}{\text{acidity or basicity of the chemical}}\]

Complete answer:
- In the question it is given to find the equivalent weight of the oxalic acid by observing the given chemical equation.
- The given chemical reaction is as follows.
\[{{H}_{2}}{{C}_{2}}{{O}_{4}}+Ca{{(OH)}_{2}}\to Ca{{C}_{2}}{{O}_{4}}+{{H}_{2}}O\]
- In the above chemical oxalic acid is going to react with one mole of calcium hydroxide and forms one mole of calcium oxalate compound as the product.
- In the above chemical reaction we can see clearly that the two hydrogens in the oxalic acid are going to react with two hydroxyl groups of the calcium hydroxide and forms two moles of water molecules as the product.
- Means oxalic acid is going to lose two hydrogens so the acidity of the oxalic acid is 2.
- The molecular weight of the oxalic acid is 90.
- The equivalent weight of the oxalic acid from the given chemical reaction is as follows.
\[\begin{align}
  & \text{Equivalent weight of oxalic acid = }\dfrac{\text{Molecular weight of the oxalic acid}}{\text{acidity of the oxalic acid}} \\
 & =\dfrac{90}{2} \\
 & =45 \\
\end{align}\]
- Therefore the equivalent weight of the oxalic acid is 45.

So, the correct option is B.

Note:
Acidity of a chemical is nothing but the number of hydrogen atoms it can lose when the chemical is going to participate in a chemical reaction. Acidity or basicity of a chemical is going to decide the equivalent weight of the respective chemical.