Question

$5.00\, mL$ of $0.10 \,M$ oxalic acid solution taken in a conical flask is titrated against $NaOH$ from a burette using phenolphthalein indicator. The volume of $NaOH$ required for the appearance of permanent faint pink color is tabulated below for five experiments. What is the concentration, in molarity, of the $NaOH$ solution?

Exp. No.	Vol. of $NaOH(mL)$
1	12.5
2	10.5
3	9.0
4	9.0
5	9.0

Answer 1

No. of eq. of oxalic acid $=$ No. of eq. of $NaOH$
or $\frac{5.00 \times 0.10}{1000} \times 2=\frac{9.0 \times M}{1000} \times 1$
$\therefore $ Molarity of $NaOH$ solution $=\frac{1}{9}$
$=0.11 \,M$