The disodium salt of ethylene diamine tetraacetic acid can be used to estimate the following ion$(s)$ in an aqueous solution:

$20 \, mL$ of a solution of a weak monobasic acid neutralizes $22.18 \, mL$ of a solution of $NaOH$,and $20 \, mL$ of $N/10$ $HCl$ neutralizes $21.5 \, mL$ of the same $NaOH$ solution. The normality of the acid is nearly $.......$ $N$.

The reagent commonly used to determine the hardness of water titrimetrically is

$K_2Cr_2O_7$ is preferred over $Na_2Cr_2O_7$ for use in volumetric analysis as a primary standard because

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

$A$ $0.166 \ g$ sample of an organic compound was digested with conc. $H_2SO_4$ and then distilled with $NaOH$. The ammonia gas evolved was passed through $50.0 \ mL$ of $0.5 \ N \ H_2SO_4$. The excess acid required $30.0 \ mL$ of $0.25 \ N \ NaOH$ for complete neutralization. The mass percentage of nitrogen in the organic compound is $..... \ \%$.