Which of the following combinations does not evolve $Cl_2$ gas?

$KMnO_4$ acts as an oxidising agent in acidic medium. $X$ is the difference between the oxidation states of $Mn$ in reactant and product. $Y$ is the number of $d$ electrons present in the brown red precipitate formed at the end of the acetate ion test with neutral ferric chloride. The value of $X+Y$ is $.........$

Which one of the following reactions does not take place?

Which of the following processes does not involve oxidation of iron?

$200 \ mL$ of $x \times 10^{-3} \ M$ potassium dichromate $(K_2Cr_2O_7)$ is required to oxidise $750 \ mL$ of $0.6 \ M$ Mohr's salt $(FeSO_4 \cdot (NH_4)_2SO_4 \cdot 6H_2O)$ solution in acidic medium. Here $x =$ ?

Consider the following redox reaction in basic medium.
$x \ Cr(OH)_3 + y(IO_3)^{-} + z(OH)^{-} \rightarrow a(CrO_4)^{2-} + b(I)^{-} + c(H_2O)$
The incorrect option about it is