Question

An aqueous solution of 12.6 g of oxalic acid dihydrate $\left(C_2{H}_2{O}_4.2H_{2}O\right)$ has a volume equal to 250 mL. The volume of 0.1 M $NaOH$ required to completely neutralize 20 mL of this solution is:

• A. 160 mL
• B. 80 mL
• C. 140 mL
• D. 120 mL

Answer 1

The correct option is A 160 mL

Number of moles of oxalic acid dihydrate ($C_2{H}_2{O}_4.2H_{2}O)$ = $\frac{12.6}{126}=0.1mol$

Molarity of oxalic acid solution = $\frac{\text{number of moles}}{\text{volume of solution in mL}}\times 1000$
$=\frac{0.1}{250}\times 1000=0.4M$

Since, the resultant solution will be neutral and 1 mol of oxalic acid gives 2 mol of $H^{+}$ ion, Similarly 1 mol of $NaOH$ gives 1 mol of $O{H}^{-}$ ion
$M_1{V}_1=M_2{V}_2$

where $M_1$ and $V_1$ are the molarity of $H^{+}$ ion and the volume of the acid solution, respectively.
$M_2$ and $V_2$ are the molarity of $O{H}^{-}$ ion and the volume of the basic solution, respectively.
$(2\times 0.4\times 20)=(1\times 0.1\times V_2)$
On solving, volume of $NaOH$ ($V_2$) = 160 mL

Therefore, 160 mL of 0.1 M $NaOH$ is required to neutralize the oxalic acid solution.