Question 5 of 31advanced🔍 AnalyzeLong Answer5 marks

Which of the following species, do not show disproportionation reaction and why? ClO⁻, ClO₂⁻, ClO₃⁻ and ClO₄⁻. Also write reaction for each of the species that disproportionates.

Correct Answer

Among the given oxoanions of chlorine, ClO4−ClO_4^- does not show a disproportionation reaction. This is because, in this oxoanion, chlorine is present in its highest oxidation state of +7. Since chlorine cannot be oxidized to any higher state, it cannot undergo disproportionation.

The other three species, ClO−ClO^-, ClO2−ClO_2^-, and ClO3−ClO_3^-, undergo disproportionation because the oxidation state of chlorine in these species is intermediate and can simultaneously increase and decrease.

For ClO−ClO^-, the oxidation state of chlorine changes from +1 to -1 and +5. The reaction is:

3ClO−→2Cl−+ClO3−3ClO^- \rightarrow 2Cl^- + ClO_3^-

For ClO2−ClO_2^-, the oxidation state of chlorine changes from +3 to +5 and -1. The reaction is:

6ClO2−→hv4ClO3−+2Cl−6ClO_2^- \xrightarrow{hv} 4ClO_3^- + 2Cl^-

For ClO3−ClO_3^-, the oxidation state of chlorine changes from +5 to -1 and +7. The reaction is:

4ClO3−→Cl−+3ClO4−4ClO_3^- \rightarrow Cl^- + 3ClO_4^-
Exercise: Problem 7.5 | Q: Problem 7.5 | (Page Page 10)
For More Understanding

Explanation

Disproportionation requires an element to be in an intermediate oxidation state so it can be both oxidized and reduced simultaneously. In ClO4−ClO_4^-, chlorine is in its maximum oxidation state of +7, preventing further oxidation. The other oxoanions have chlorine in intermediate states (+1, +3, +5) and thus disproportionate into a higher and a lower oxidation state of chlorine.

Solution Steps

  1. Step 1: Identify the species that does not disproportionate. ClO4−ClO_4^- does not disproportionate because chlorine is in its highest oxidation state of +7.

  2. Step 2: Write the disproportionation reaction for ClO−ClO^-: 3ClO−→2Cl−+ClO3−3ClO^- \rightarrow 2Cl^- + ClO_3^-

  3. Step 3: Write the disproportionation reaction for ClO2−ClO_2^-: 6ClO2−→hv4ClO3−+2Cl−6ClO_2^- \xrightarrow{hv} 4ClO_3^- + 2Cl^-

  4. Step 4: Write the disproportionation reaction for ClO3−ClO_3^-: 4ClO3−→Cl−+3ClO4−4ClO_3^- \rightarrow Cl^- + 3ClO_4^-

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