Why in the redox titration of $KMnO_4$ vs oxalic acid,do we heat the oxalic acid solution before starting the titration?

In a titration experiment,$10 \, mL$ of an $FeCl_{2}$ solution consumed $25 \, mL$ of a standard $K_{2}Cr_{2}O_{7}$ solution to reach the equivalence point. The standard $K_{2}Cr_{2}O_{7}$ solution is prepared by dissolving $1.225 \, g$ of $K_{2}Cr_{2}O_{7}$ in $250 \, mL$ water. The concentration of the $FeCl_{2}$ solution is closest to $..... \, N$
[Given : molecular weight of $K_{2}Cr_{2}O_{7} = 294 \, g \, mol^{-1}$]

Eosin used to detect the end point of precipitation titration by adsorption is called:

When $10 \ mL$ of an aqueous solution of $Fe^{2+}$ ions was titrated in the presence of dil $H_{2}SO_{4}$ using diphenylamine indicator,$15 \ mL$ of $0.02 \ M$ solution of $K_{2}Cr_{2}O_{7}$ was required to get the end point. The molarity of the solution containing $Fe^{2+}$ ions is $X \times 10^{-2} \ M$. The value of $x$ is $....$ (Nearest integer)

During the estimation of oxalic acid $Vs$ $KMnO_4$,the self-indicator is:

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