Which of the following is not a disproportionation reaction?

• A

  $\mathrm{Hg}_2 \mathrm{Cl}_2 \longrightarrow \mathrm{Hg}+\mathrm{HgCl}_2$
• B

  $4 \mathrm{H}_3 \mathrm{PO}_3 \longrightarrow 3 \mathrm{H}_3 \mathrm{PO}_4+\mathrm{PH}_3$
• C

  $\mathrm{Cl}_2+2 \mathrm{NaOH} \longrightarrow \mathrm{NaCl}+\mathrm{NaOCl}+\mathrm{H}_2 \mathrm{O}$
• Correct answer
  D

  $\mathrm{BaO}_2+\mathrm{H}_2 \mathrm{SP}_4 \longrightarrow \mathrm{BaSO}_4+\mathrm{H}_2 \mathrm{O}_2$

Solution

(iv) $\mathrm{BaO}_2+\mathrm{H}_2 \mathrm{SO}_4 \rightarrow \mathrm{BaSO}_4+\mathrm{H}_2 \mathrm{O}_2$; Displacement reaction.

Hence, the correct answer is option: 'D'.