Which of the following is used as a white pigment?

Which transition element of the $3d$ series is used in a dry battery cell?

Which one of the following statements is correct when $SO_2$ is passed through acidified $K_2Cr_2O_7$ solution?

Oxidation states of the metal in the minerals haematite and magnetite,respectively,are

The colour and magnetic nature of manganate ion $MnO_4^{2-}$ is-

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 ......... .