$KMnO_4$ 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 $..........$.

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 ammonia evolved from the treatment of $0.30 \, g$ of an organic compound for the estimation of nitrogen was passed in $100 \, mL$ of $0.1 \, M$ sulphuric acid. The excess of acid required $20 \, mL$ of $0.5 \, M$ sodium hydroxide solution for complete neutralization. The organic compound is:

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

Iodine and hypo react to produce

Estimation of $CO$ is done by using: