The indicator used during the estimation of $COD$ of a water sample is

The indicator used in the titration of iodine against sodium thiosulphate is

Two acids $A$ and $B$ are titrated separately. $25 \ mL$ of $0.5 \ M \ Na_2CO_3$ solution requires $10 \ mL$ of $A$ and $40 \ mL$ of $B$ for complete neutralization. The volumes (in $L$) of $A$ and $B$ required to produce $1 \ L$ of $1 \ N$ acid solution respectively are:

In the titration of potassium permanganate $(KMnO_4)$ against ferrous ammonium sulphate $(FAS)$ solution,dilute sulphuric acid $(H_2SO_4)$ but not nitric acid $(HNO_3)$ is used to maintain an acidic medium,because:

Consider the titration of $NaOH$ solution versus $1.25\, M$ oxalic acid solution. At the end point,the following burette readings were obtained:
$(i)$ $4.5\, mL$ $\quad (ii)$ $4.5\, mL$ $\quad (iii)$ $4.4\, mL$
$(iv)$ $4.4\, mL$ $\quad (v)$ $4.4\, mL$
If the volume of oxalic acid taken was $10.0\, mL$,then the molarity of the $NaOH$ solution is .... $M$ (Rounded-off to the nearest integer).

For standardizing $NaOH$ solution,which of the following is used as a primary standard?