Question

0.16 g of dibasic acid requires 25 mL decimolar NaOH solution for complete neutralisation. The molecular mass of the acid is

• A. 256
• B. 64
• C. 32
• D. 128

Answer 1

Answer: (D)

$0.16g$ of dibasic acid is neutralised by
$=25mL$ of $0.1MNaOH$
$H_{2}X+2NaOH=N{a}_{2}X+H_{2}O$
Millimoles of acid $=\frac{1}{2}\times$ millimoles of $NaOH$
$NaOH=\frac{1}{2}\times 25\times 0.1=1.25$
Now, millimoles $=\frac{W_{mg}}{\text{Mol.mass}}$
or Mol mass $=\frac{W_{mg}}{\text{millimoles}}$
$=\frac{0.16\times 1000}{1.25}$
$=128$