$30 \ mL$ of acid solution is neutralized by $15 \ mL$ of a $0.2 \ N$ base. The strength of acid solution is $.............. \ N$.

The volume of $\frac{N}{10}$ $NaOH$ required to neutralize $100 \ mL$ of $\frac{N}{25}$ $HCl$ is......$mL$

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:

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

Of all the three common mineral acids,only sulphuric acid is found to be suitable for making the solution acidic in redox titrations involving $KMnO_4$ because:

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