Question

Given, $1.25g$ of dibasic acid is completely neutralized by $25ml$ of $0.25molar$ $Ba{\left( {OH} \right)_2}$ solution. Then calculate the molecular mass of the acid.

Answer 1

We have to remember that an acid that has two acidic hydrogen atoms in its molecules. Sulfuric (${H_2}S{O_4}$) and carbonic (${H_2}C{O_3}$) acids are common examples. Neutralization reaction is a chemical reaction in which acid and a base react quantitatively with each other.

Complete answer:
We need to know that in a neutralization reaction, in a reaction in water, neutralization results in there being no excess of hydrogen or hydroxide ions present in the solution. The pH of the neutralized solution depends on the acid strength of the reactants. In a chemical reaction the term neutralization is used for a reaction between an acid and a base or alkali. Historically, this reaction was represented as
$acid + base\left( {alkali} \right) \to salt + water$
The formation of acid salts may be elucidated by the following considerations. Most of the inorganic acids combine with bases in such a manner that 1 atom of the acid is united with 1 atom of a metallic oxide, so that they may be termed monobasic acids.
As the mass of solid dibasic acid $= 1.25g$ (given)
Let molecular mass of acid is M.
So for complete neutralization,
Equivalent of acid = Equivalent of base
Or, mass of acid/equivalent weight of acid = mass of base/equivalent weight of base
Or, n-factor of acid × mole of acid = n-factor of base × mole of base
Or,$2 \times \dfrac{{1.25}}{M} = 2 \times \dfrac{{25}}{{1000}}litre \times 0.25molar$
or, $M = 1000 \times \dfrac{{1.25}}{{(25 \times 0.25)}}$
$M = \dfrac{{125000}}{{625}}$
On simplification we get,
$M = 200g/mol$
Hence, molecular mass $= 200g/mol$

Note:
We have to know that certain acids, however, exist of which an instance has already presented itself in the pyrophosphoric, 1 atom of which possesses the power of combining with 2 atoms of base; such acids are hence termed basic. Numerous acids of this class are found among those obtained from the vegetables and the animal kingdoms tartaric acid and malic acid are examples of this kind.