Question

$1.575$ gm of an organic acid was dissolved in $250$ ml of water. Further, $20$ ml of this solution required $16$ ml of $\frac{N}{8}$ alkali solution for complete neutralisation. If the basicity of the acid is $2$, find its molecular mass.

Answer 1

$16$ ml of $\frac{N}{8}$ alkali solution $\equiv$ $20$ ml of acid solution
So, $2$ ml of $1$ N alkali solution $\equiv$ $20$ ml of acid solution
$\frac{2\times 250}{20}ml$ of $1$ N alkali solution $\equiv$ $250$ ml of acid solution
$25$ ml of $1$ N alkali solution = $1.575$ gms acid
$1000$ ml of $1$ N alkali solution $=\frac{1.575}{25}\times 1000gm$ acid
Equivalent mass of the acid = $63$ gm acid
Molecular mass of the acid = Ew $\times$ basicity $=63\times 2=126$
Thus, the molecular mass of the acid is $126$ g/mol.