The oxoanion which contains all equivalent $M-O$ bonds is:
$(I)$ $CrO_4^{2-}$
$(II)$ $MnO_4^-$
$(III)$ $Cr_2O_7^{2-}$

The fusion of chromite ore $(FeCr_{2}O_{4})$ with $Na_{2}CO_{3}$ in air gives a yellow solution upon addition of water. Subsequent treatment with $H_{2}SO_{4}$ produces an orange solution. The yellow and orange colours,respectively,are due to the formation of

When a chromite ore $(A)$ is fused with sodium carbonate in free excess of air and the product is dissolved in water,a yellow solution of compound $(B)$ is obtained. After treatment of this yellow solution with sulphuric acid,compound $(C)$ can be crystallised from the solution. When compound $(C)$ is treated with $KCl$,orange crystals of compound $(D)$ crystallise out. Identify $A$ to $D$ and also explain the reactions.

Match Column $A$ with Column $B$:

Column $A$	Column $B$
$(1)$ Brass	$(a)$ $Ni$ $(60\%)$,$Cr$ $(40\%)$
$(2)$ Bronze	$(b)$ $Cu$ $(80\%)$,$Sn$ $(20\%)$
$(3)$ Cupronickel	$(c)$ $Cu$ $(90\%)$,$Sn$ $(10\%)$
$(4)$ Nichrome	$(d)$ $Cu$ $(70\%)$,$Zn$ $(30\%)$
	$(e)$ $Cu$ $(75-85\%)$,$Ni$ $(15-25\%)$

In a borax bead test under hot condition,a metal salt is heated at point $B$ of the flame,resulting in a green-coloured salt bead. The spin-only magnetic moment value of the salt is $..........$ $BM$ (Nearest integer). [Given atomic number of $Cu=29, Ni=28, Mn=25, Fe=26$]

Which of the following oxides is amphoteric?