What are secondary standard solutions?

In a titration experiment, $10 \mathrm{mL}$ of an ${\mathrm{FeCl}}_2$ solution consumed $25 \mathrm{mL}$ of a standard ${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$ solution to reach the equivalent point. The standard ${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$ solution is prepared by dissolving $1.225 \mathrm{g}$ of ${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$ in $250 \mathrm{mL}$ water. The concentration of the ${\mathrm{FeCl}}_2$ solution is closest to

[Given : molecular weight of ${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7=294 \mathrm{g} {\mathrm{mol}}^{-1}$]

In the given chemical reaction, colors of the${\mathrm{Fe}}^{2+}$ and ${\mathrm{Fe}}^{3+}$ ions, are respectively :

$5{\mathrm{Fe}}^{2+}+{\mathrm{MnO}}_4^{-}+8{\mathrm{H}}^{+}\to {\mathrm{Mn}}^{2+}+4{\mathrm{H}}_2\mathrm{O}+5{\mathrm{Fe}}^{3+}$

For kinetic study of the reaction of iodide ion with ${\mathrm{H}}_2{\mathrm{O}}_2$ at room temperature :

(A) Always use freshly prepared starch solution.

(B) Always keep the concentration of sodium thiosulphate solution less than that of $\mathrm{KI}$ solution.

(C) Record the time immediately after the appearance of blue colour.

(D) Record the time immediately before the appearance of blue colour.

(E) Always keep the concentration of sodium thiosulphate solution more than that of $\mathrm{KI}$ solution.

Choose the correct answer from the options given below

$20 \mathrm{mL}$ of $0.02 \mathrm{M}$ hypo solution is used for the titration of $10 \mathrm{mL}$ of copper sulphate solution, in the presence of excess of $\mathrm{KI}$ using starch as an indicator. The molarity of ${\mathrm{Cu}}^{2+}$ is found to be $\_\_\_\_\_\times {10}^{-2}\mathrm{M}$ (nearest integer)

Given : $$\begin{gathered} 2{\mathrm{Cu}}^{2+}+4{\mathrm{I}}^{-}\to {\mathrm{Cu}}_2{\mathrm{I}}_2+{\mathrm{I}}_2 \\ {\mathrm{I}}_2 + 2{\mathrm{S}}_2{\mathrm{O}}_3^{-2} \to 2{\mathrm{I}}^{—} + {\mathrm{S}}_4{\mathrm{O}}_6^{-2} \end{gathered}$$