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

Why is it necessary to wash the precipitate before measuring it quantitatively?

When nitrogen gas is passed through $100 \ mL$ of $0.1 \ M$ $H_2SO_4$ containing $0.30 \ g$ of an organic compound,the ammonia evolved is neutralized. To neutralize the excess acid,$20 \ mL$ of $0.5 \ M$ $NaOH$ is required. Identify the organic compound.

When potassium permanganate is titrated against ferrous ammonium sulphate,the equivalent weight of potassium permanganate is

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:

The functional groups that are responsible for the ion-exchange property of cation and anion exchange resins,respectively,are :