$3.92 \, g$ of ferrous ammonium sulphate crystals are dissolved in $100 \, mL$ of water. $20 \, mL$ of this solution requires $18 \, mL$ of $KMnO_4$ during titration for complete oxidation. The weight of $KMnO_4$ present in one litre of the solution is ............. $g$.

Which reagent is commonly used in titration to determine the hardness of water?

An aqueous solution of oxalic acid dihydrate contains $6.3 \ g$ in $250 \ mL$. The volume of $0.1 \ N \ NaOH$ required to completely neutralize $10 \ mL$ of this solution is $.............. \ mL$.

In the titration of a strong acid and a weak base,the indicator used is:

In an acidic medium, $10 mL$ of $0.25 M$ oxalic acid is titrated with $KMnO_4$ solution. If the volume of $KMnO_4$ solution required to reach the end point is $10 mL$, the strength of the $KMnO_4$ solution is (in $M$)

$5.00 \ mL$ 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?

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