In the structure of the dichromate ion,there is a :

What is the starting material for the preparation of $KMnO_4$?

Identify the factor responsible for the colour of transition metal compounds.

Which of the following compounds is used as the starting material for the preparation of potassium dichromate?

On heating a mixture of common salt and $K_{2}Cr_{2}O_{7}$ with concentrated $H_{2}SO_{4}$, a gas is evolved. The formula of the gas evolved and the oxidation state of the central metal atom in the gas, respectively, are:

When $Cu^{2+}$ ion is treated with $KI$,a white precipitate,$X$ appears in solution. The solution is titrated with sodium thiosulphate,the compound $Y$ is formed. $X$ and $Y$ respectively are