question_answer

Hydrogen peroxide acts both as an oxidising agent and as reducing agent in alkaline solution towards certain first row transition metal ions. Illustrate both these properties of \[{{H}_{2}}{{O}_{2}}\] using chemical equation.

Answer:

                \[{{H}_{2}}{{O}_{2}}\] as oxidising agent in alkaline medium. It oxidises manganese sulphate to manganese dioxide in the presence of an alkali \[MnS{{O}_{4}}+{{H}_{2}}{{O}_{2}}+2NaOH\xrightarrow{{}}Mn{{O}_{2}}+N{{a}_{2}}S{{O}_{4}}+2{{H}_{2}}O\] \[M{{n}^{2+}}\,+{{H}_{2}}{{O}_{2}}\,+2O{{H}^{-}}\xrightarrow{\,}\,Mn{{O}_{2}}+2{{H}_{2}}O\]                   (Ionic equation) \[{{H}_{2}}{{O}_{2}}\] as reducing agent in alkaline medium. It reduces potassium ferricyanide to potassium ferrocyanide in the presence of an alkali \[2{{K}_{3}}[Fe{{(CN)}_{6}}]+2KOH+{{H}_{2}}{{O}_{2}}\xrightarrow{{}}2{{K}_{4}}[Fe{{(CN)}_{6}}]+2{{H}_{2}}O+{{O}_{2}}\] \[2{{[Fe{{(CN)}_{6}}]}^{3-}}+2O{{H}^{-}}+{{H}_{2}}{{O}_{2}}\xrightarrow{{}}\,2{{[Fe{{(CN)}_{6}}]}^{4-}}\,+2{{H}_{2}}O+{{O}_{2}}\]                                                      (Ionic equation)