In which of the following reactions does the oxidation number not change?

In the following reaction,$\text{SO}_2 + 2\text{H}_2\text{S} \to 3\text{S} + 2\text{H}_2\text{O}$,which choice has a value twice that of the equivalent mass of the oxidising agent?

$A$ 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?

When hypo solution is added to cupric sulphate solution,the blue colour of the latter is discharged,due to the formation of:

$KMnO_4$ (acidified) $+ HCl \rightarrow H_2O + X_{(g)},$ $X$ is a

Explain the uses of indicators in the analysis of redox reactions.