When $SO_2$ gas is passed through an acidic solution of $K_2Cr_2O_7$,what is the change in the oxidation state of chromium?

In the equation,$BiO_3^{-} + 6H^{+} + xe^{-} \rightarrow Bi^{3+} + 3H_2O$. What is the value of $x$?

In the following balanced chemical reaction,$IO_3^- + aI^- + bH^+ \to cH_2O + dI_2$,what are the values of $a, b, c$ and $d$ respectively?

Assign $A$,$B$,$C$,$D$ from the given type of reaction.
$PbO_2 + 4HNO_3 (Conc.) \longrightarrow Pb(NO_3)_2 + 2H_2O + O_2$

Write the balanced chemical equations for the following reactions:
$(1)$ Reaction of $Cr_2O_7^{2-}$ with $Fe^{2+}$ in acidic medium.
$(2)$ Reaction of $MnO_4^-$ with $Fe^{2+}$ in acidic medium.

In neutral or faintly alkaline medium,$KMnO_4$ being a powerful oxidant can oxidize thiosulphate almost quantitatively to sulphate. In this reaction,the overall change in the oxidation state of manganese will be: