Question

$0.16g$ of dibasic acid requires $25mL$ 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 $NaOH$
$=\frac{1}{2}\times 25\times 0.1=1.25$
$\because$ Millimoles $=\frac{W(mg)}{\text{mol . mass }}$
$\therefore$ Mol. mass $=\frac{W(mg)}{\text{ millimoles }}$
$=\frac{0.16\times 1000}{1.25}=128$