Animated Solution for Chemistry - Redox Reactions: ${\text{MnO}}_4^{-}$ is a good oxidising agent in different medium changing to ${\text{MnO}}_4^{-}⟶{\text{Mn}}^{2+}$ $⟶{\text{MnO}}_4^{2-}$ $⟶{\text{MnO}}_2$ $⟶{\text{Mn}}_2{\text{O}}_3$ Changes in oxidation number respectively, are

Manganese is a fascinating transition metal. It can exhibit a wide range of oxidation states, from $+2$ all the way up to $+7$. This incredible versatility makes the permanganate ion (${\text{MnO}}_4^{-}$) one of the most powerful and widely used oxidizing agents in chemistry.

Depending on the pH of the medium—whether it is strongly acidic, faintly basic, or neutral—${\text{MnO}}_4^{-}$ can get reduced to different products. In this problem, we are given four different reduction products and we need to find the change in the oxidation number of Manganese for each case.

Before we dive into the calculations, let's recall the fundamental rule for finding oxidation states.

For oxygen, unless it is in a peroxide or superoxide, we can safely assume its oxidation state is $-2$. With this tool in our arsenal, we can unlock the oxidation state of Manganese in any compound.

Let's start with our reactant, the permanganate ion, ${\text{MnO}}_4^{-}$.

Let the oxidation state of Manganese be $x$. There are four oxygen atoms, each contributing $-2$, and the overall charge of the ion is $-1$.

Setting up the equation:

So, Manganese starts its journey from a highly oxidized state of $+7$.

Now, let's evaluate each product one by one and find the change in oxidation number.

Here, Manganese is present as a simple monoatomic ion. The oxidation state is simply the charge on the ion, which is $+2$.

The change in oxidation state is the absolute difference between the initial and final states:

This is the manganate ion. Let's set up our equation again.

The change here is:

Manganese dioxide is a neutral molecule, so the sum of oxidation states is zero.

The change is:

In this compound, we have two Manganese atoms. We must account for both in our equation.

The change is:

We have successfully calculated the change in oxidation number for all four reactions.

The sequence of changes is 5, 1, 3, 4.

Looking at our options, this perfectly matches option (c). The beauty of redox reactions lies in this simple electron accounting. By keeping track of the oxidation states, we can easily determine how many electrons are transferred in any chemical process.