Question

$KMn{O_4}$​can be prepared from ${K_2}Mn{O_4}$ ​ as per the reaction
$3Mn{O_4}^{2 - } + 2{H_2}O \rightleftharpoons 2Mn{O_4} + Mn{O_2} + 4O{H^ - }$
The reaction can go to completion by removing OH− ions by adding:

$${A.{\text{ }}HCl} \\\ {B.{\text{ }}KOH} \\\ {C.{\text{ }}CO2} \\\ {D.{\text{ }}SO2}$$

Answer 1

Hint : We must understand that fuels with a higher octane rating are used in high-performance gasoline engines that run with higher compression ratios. Fuels with lower octane numbers are best suited for diesel engines, because diesel engines do not compress the fuel.

Complete step by step solution :
The oxidation of manganate ions to permanganate ions will go to completion by removing hydroxide ions.
Hydroxide ion removal can be accomplished by adding$C{O_2}$. This is because the addition of carbon dioxide to hydroxide ions will generate carbonate ions and water molecules.
$C{O_2} + 2OH - \to CO{3^{2 - }}{\text{ }} + {H_2}O.$
As we know that a weak acid is required to remove $O{H^ - }$ions as a strong acid will reverse the reaction. So, $HCl$is a strong acid so it will reverse the reaction whereas sulphur dioxide, $S{O_2}$will react with water to form a strong sulphuric acid,${H_2}S{O_4}$.
Potassium hydroxide, $KOH$, is a strong base which will ultimately elevate the $O{H^ - }$ion concentration in solution and reaction may move more backward side direction.
Removal carbonate ions formed after reacting carbon dioxide to hydroxide ions are easy to remove from the system.
Hence, we can conclude that the reaction can go to completion by removing $O{H^ - }$ ions by adding$C{O_2}$.
Therefore, the correct option is C. $C{O_2}$

Note : We must remember that the$HCl$ and $S{O_2}$are reducing agents and thus they can reduce$Mn{O^{4 - }}$. Also $C{O_2}$ is colorless gas which neither oxidising nor reducing agent, and by forming carbonate ions it will provide acidic medium only. Therefore, the climate change is major problem of too much carbon dioxide in the atmosphere which causes acid rain.