The weight of potassium dichromate (molecular weight $= 294$) required to prepare $250 \ mL$ of $0.04 \ N$ solution is (in $g$)

$2.52 \ g$ of oxalic acid dihydrate was dissolved in $100 \ mL$ of water. $10 \ mL$ of this solution was diluted to $500 \ mL$. The normality of the final solution (in $N$) and the amount of oxalic acid (in $mg/mL$) in the solution are respectively

Below are two statements. One is labeled as Assertion $(A)$ and the other as Reason $(R).$
Assertion $(A):$ When using an aqueous solution of $KOH$ in a volumetric analysis,its concentration should be checked before use.
Reason $(R):$ $KOH$ solution absorbs atmospheric $CO_2$ when it gets old.
In the context of the above statements,choose the correct answer from the options given below:

$500 \ mL$ of $1.2 \ M$ $KI$ solution is mixed with $500 \ mL$ of $0.2 \ M$ $KMnO_4$ solution in basic medium. The liberated iodine was titrated with standard $0.1 \ M$ $Na_2S_2O_3$ solution in the presence of starch indicator till the blue color disappeared. The volume (in $L$) of $Na_2S_2O_3$ consumed is . . . . . . . (Nearest integer)

Identify the correct statements:
$A$. Hydrated salts can be used as primary standard.
$B$. Primary standard should not undergo any reaction with air.
$C$. Reactions of primary standard with another substance should be instantaneous and stoichiometric.
$D$. Primary standard should not be soluble in water.
$E$. Primary standard should have low relative molar mass.
Choose the correct answer from the options given below :

$KMnO_4$ is titrated with ferrous ammonium sulphate hexahydrate in the presence of dilute $H_2SO_4$. The number of water molecules produced for $2$ molecules of $KMnO_4$ is $..........$.