In neutral or faintly alkaline medium, KMnO4 being a powerful oxidant can oxidize, thiosulphate almost quantitatively, to sulphate. In this reaction overall change in oxidation state of manganese will be
The question involves determining the change in the oxidation state of manganese in the reaction of potassium permanganate (KMnO4) with thiosulfate in a neutral or faintly alkaline medium. This can be solved by understanding the oxidation-reduction behavior of manganese in this chemical reaction.
In a neutral or faintly alkaline medium, potassium permanganate (KMnO4) acts as a strong oxidizing agent. The oxidation state of manganese in KMnO4 is +7. During the reaction with thiosulfate, manganese is reduced. We need to determine the oxidation state to which it is reduced.
The overall balanced reaction in a neutral or faintly alkaline medium is: \(\text{2 KMnO}_4 + \text{3 Na}_2\text{S}_2\text{O}_3 + \text{2 H}_2\text{O} \rightarrow \text{2 MnO}_2 + \text{3 Na}_2\text{SO}_4 + \text{2 KOH}\)
In the above reaction, manganese goes from an oxidation state of +7 in KMnO4 to an oxidation state of +4 in MnO2. Thus, the change in oxidation state of manganese is: \(+7 - (+4) = +3\).
The overall change in the oxidation state of manganese in this reaction is 3.
Hence, the correct answer is 3.
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Under neutral or slightly alkaline conditions, thiosulfate undergoes nearly complete oxidation to form sulfate ions, as indicated by the following reaction: \(8MnO_{4}^−+3S_2O_{3}^{2−}+H_2O→8MnO_2+6SO_{4}^{2−}+2OH^−\) Here the Mn changes from Mn+7 to Mn+4 Thus, overall change in its oxidation number would be of 3. So, the correct option is (D): 3
Redox reactions are chemical reactions where oxidation and reduction take place simultaneously. In this type of reaction, there is a gain of electrons for one chemical species while the other loses electrons or simply involves transfer of electrons. The species that loses electrons is oxidized while the one that gains electrons is reduced.
Types of Redox Reactions:
Redox reactions can be differentiated into 4 categories namely combination reactions, decomposition reactions, displacement reactions, and disproportionation reactions. Each is explained separately below:
Combination Reaction:
In this, the molecules combine to form new compounds. For example, when magnesium reacts to nitrogen.
Decomposition Reaction:
Opposite to the combination reaction, here there is a breakdown of compounds to simpler substances. For example, electrolysis of water.
Displacement Reaction:
In this, the more reactive metal will displace the less reactive one in a chemical reaction. The reactivity of an element is represented in a series called the reactivity series (arranged in decreasing order of reactivity) which makes it easier to determine the chemical reaction and its products.
Disproportionation Reaction:
This is a peculiar type of reaction where an element showing a particular oxidation state will be oxidized and reduced simultaneously. Another thing to note is that these reactions will always have an element that can exhibit three oxidation states.
