The amphoteric oxide among $V_2O_3$,$V_2O_4$,and $V_2O_5$ upon reaction with alkali leads to the formation of an oxide anion. The oxidation state of $V$ in the oxide anion is:

Which of the following statements is incorrect?

What is the use of potassium permanganate $(KMnO_4)$?

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

The colour of $K_2Cr_2O_7$ changes from red-orange to lemon-yellow on treatment with aqueous $KOH$ because of:

State the uses of zinc and iron.