Chlorine is used to purify drinking water. Excess of chlorine is harmful. The excess of chlorine is removed by treating with sulphur dioxide. Present a balanced equation for this redox change taking place in water.
The given redox reaction can be represented as: \(Cl_2(s)+SO_2(aq)+H_2O\rightarrow Cl^−(aq)+SO^{2−}_4(aq)\)
The oxidation half reaction is: \(\overset{+4}SO_2(aq)\rightarrow \overset{+6}SO_4^{2−}(aq)\)
The oxidation number is balanced by adding two electrons as: \(SO_2(aq)\rightarrow SO_4^{2−}(aq)+2e^−\)
The charge is balanced by adding \(4H ^+\) ions as: \(SO_2(aq)\rightarrow SO_4^{2−}(aq)+4H^+(aq)+2e^−\)
The \(O\) atoms and \(H ^+\) ions are balanced by adding \(2H_2O\) molecules as: \(SO_2(aq)+2H_2O(l)\rightarrow SO_4^{2−}(aq)+4H^+(aq)+2e^−\) ………(i)
The reduction half reaction is: \(Cl_2(s)\rightarrow Cl^−(aq)\)
The chlorine atoms are balanced as: \(\overset{0}Cl_2(s)\rightarrow \overset{-1}Cl^−(aq)\)
The oxidation number is balanced by adding electrons \(Cl_2(s)+2e^−\rightarrow 2Cl^ -(aq)\)… (ii) The balanced chemical equation can be obtained by adding equation (i) and (ii) as: \(Cl_2(s)+SO_2(aq)+2H_2O(l)\rightarrow2Cl^−(aq)+SO_4^{2−}(aq)+4H^+(aq)\)
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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.
