Question

Normality of a solution that contains 12.64g of ${KMn{O_4}}$ in 500ml of solution, to be used in a reaction that produces $ MnO_4^{2 - } $ ions as reduced product, is:
(A) 0.16N
(B) 0.32N
(C) 0.80N
(D) 0.08N

Answer 1

Hint: In some chemical solutions, NORMALITY and MOLARITY are equivalent or N=M. This situation typically occurs when N=1 and converting molarity to normality matters only when the number of equivalent changes by ionization. Here, the basicity refers to the number of H+ ions that can be given by an acid molecule.

Complete step by step solution:
$ MnO_4^ - ( + 7) \to MnO_4^{2 - }( + 6) $
Change in oxidation number=1 unit.
Therefore, normality=molarity.
$12.64gKMn{O_4} = 0.0.8mol{\text{ in 0}}{\text{.5L = 0}}{\text{.016M}} \\
  {\text{ = 0}}{\text{.16N}}{\text{.}} \\$
Therefore, option (A) is the right answer.
- Molarity = it is defined as the moles of complete substance per litre of solution.
- Normality = It is defined as the only moles of reactive species per litre of solution.
> The only difference lies in between normality and molarity is that normality describes the amount of gram equivalent of compound that is present in the solution while molarity describes the number of moles present in the solution.
> In short we can also say that for all solutions which have gram equivalent value of 1, the normality of the solution is always equal to the molarity of the solution.

Note: Molarity is more convenient to use in experiments with significant temperature changes because the volume of solution increases with temperature, and heating causes molarity to decrease. However, since molarity is based on masses rather than the volumes, thus molarity remains unchanged.