Though alkaline potassium permanganate and acidic potassium permanganate both are used as oxidants, yet in the manufacture of benzoic acid from toluene we use alcoholic potassium permanganate as an oxidant. Why? Write a balanced redox equation for the reaction.
When concentrated sulphuric acid is added to an inorganic mixture containing chloride, we get colourless pungent smelling gas HCl, but if the mixture contains bromide then we get red vapour of bromine. Why?
(a) In the manufacture of benzoic acid from toluene, alcoholic potassium permanganate is used as an oxidant because of the following reasons. (i) In a neutral medium, \(OH ^-\) ions are produced in the reaction itself. As a result, the cost of adding an acid or a base can be reduced.
(ii) \(KMnO_4\) and alcohol are homogeneous to each other since both are polar. Toluene and alcohol are also homogeneous to each other because both are organic compounds. Reactions can proceed at a faster rate in a homogeneous medium than in a heterogeneous medium. Hence, in alcohol, \(KMnO_4\) and toluene can react at a faster rate. The balanced redox equation for the reaction in a neutral medium is give as below:
(b) When conc. \(H_2SO_4\) is added to an inorganic mixture containing bromide, initially \(HBr\) is produced. \(HBr\), being a strong reducing agent reduces \(H_2SO_4\) to \(SO_2\) with the evolution of red vapour of bromine.
But, when conc. \(H_2SO_4\) is added to an inorganic mixture containing chloride, a pungent smelling gas \((HCl)\) is evolved. \(HCl\), being a weak reducing agent, cannot reduce \(H_2SO_4\) to \(SO_2\). \(2NaCl+2H_2SO_4\rightarrow2NaHSO_4+2HCl\)
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Top Questions on Classical Idea Of Redox Reactions – Oxidation And Reduction Reactions
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.
