When $MnO_2$ is fused with $KOH$,a coloured compound is formed. The product and its colour are:

The starting material for the manufacture of $KMnO_4$ is

The amphoteric oxide of Vanadium $(V)$ is $V_2O_5$. It reacts with alkali to form an oxoion '$X$' and with acid to form an oxoion '$Y$'. The oxidation states of '$V$' in '$X$' and '$Y$' are respectively:

In making gun-barrel,the steel used is

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

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