The yellow colour of chromates changes to orange on acidification due to the formation of:

Fill in the blanks:
$(1)$ In the dichromate ion,the $O-Cr-O$ bond angle is ....... $^o$.
$(2)$ The reaction $3Sn^{2+} \to 3Sn^{4+} + 6e^-$ occurs via .........,in which $Sn^{2+}$ is ......... .
$(3)$ The symbols for stannous and stannic are ......... and ......... respectively.
$(4)$ $V_2O_4$ dissolves in acidic compounds to give ......... salts.

Which product is formed by the reaction of an acidic solution of chromic acid with hydrogen peroxide?

$MnO^{-}_4$ is of intense pink colour,though $Mn$ is in $(+7)$ oxidation state,it is due to

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

The oxoanion in which the oxidation state of the central atom is same as its group number in the periodic table is