When copper is heated with concentrated $HNO_3$,it produces:

For the decolourization of $1 \ mole$ of $KMnO_4$,the moles of $H_2O_2$ required is: (in $.5$)

Explain why the colour of $KMnO_4$ disappears when oxalic acid is added to its solution in acidic medium.

The heating of $(NH_4)_2Cr_2O_7$ produces another chromium compound along with $N_2$ gas. The change of the oxidation state of $Cr$ in the reaction is

In the reaction $2CuSO_4 + 4KI \rightarrow Cu_2I_2 + 2K_2SO_4 + I_2$,what is the ratio of the equivalent weight of $CuSO_4$ to its molecular weight?

Balance the following redox reactions by the ion-electron method:
$(a)$ $MnO_4^-(aq) + I^{-}(aq) \rightarrow MnO_2(s) + I_2(s)$ (in basic medium)
$(b)$ $MnO_4^-(aq) + SO_2(g) \rightarrow Mn^{2+}(aq) + HSO_4^-(aq)$ (in acidic solution)
$(c)$ $H_2O_2(aq) + Fe^{2+}(aq) \rightarrow Fe^{3+}(aq) + H_2O(l)$ (in acidic solution)
$(d)$ $Cr_2O_7^{2-} + SO_2(g) \rightarrow Cr^{3+}(aq) + SO_4^{2-}(aq)$ (in acidic solution)