Among the following oxides of $3d$ elements,the number of mixed oxides are . . . . . .
$Ti_{2}O_{3}, V_{2}O_{4}, Cr_{2}O_{3}, Mn_{3}O_{4}, Fe_{3}O_{4}, Fe_{2}O_{3}, Co_{3}O_{4}$

On heating $KMnO_4$,one among the following is not formed:

Fill in the blanks:
$(1)$ ......... acid is added to perform titrations with $KMnO_4$ and $K_2Cr_2O_7$.
$(2)$ Crystals of potassium dichromate are of ......... color,while crystals of potassium chromate are of ......... color.
$(3)$ The color of $MnO_4^{2-}$ is ......... and the color of $MnO_4^-$ is ......... .

For $Cu_{2}Cl_{2}$ and $CuCl_{2}$ in aqueous medium,which of the following statements is correct?

The compounds formed when $KMnO_4$ is heated to $513 \ K$ are . . . . . .

Which of the following statements is not correct about $Cu^{2+}$ and $Cu^{+}$?