$50 \ cm^{3}$ of $0.04 \ M \ K_{2}Cr_{2}O_{7}$ in acidic medium oxidizes a sample of $H_{2}S$ gas to sulphur. The volume of $0.03 \ M \ KMnO_{4}$ required to oxidize the same amount of $H_{2}S$ gas to sulphur in acidic medium is: (in $cm^{3}$)

In the following reaction mixtures,
$I$. $Cu / CuSO_4 + Ag / Ag_2SO_4$
$II$. $Zn / ZnSO_4 + Cu / CuSO_4$
copper respectively undergoes

Which of the following act as an oxidising as well as a reducing agent?

Which reaction is $NOT$ a redox reaction?

$20 \ mL$ of $Fe^{2+}$ solution of certain concentration has completely reacted with $20 \ mL$ of $0.01 \ M \ K_2Cr_2O_7$ in acidic medium. If $20 \ mL$ of same $Fe^{2+}$ solution has reacted completely with $20 \ mL$ of $KMnO_4$ solution in acidic medium,the molarity of $KMnO_4$ solution is: (in $M$)

$A$ solution of $KMnO_4$ on reduction yields either a colourless solution,a brown precipitate,or a green solution depending on the $pH$ of the solution. What different stages of the reduction do these represent and how are they carried out?