Which of the following is not a redox reaction? (a) CaCO CaO CO → (b) O 2H 2H O → (c) Na H O NaOH H → (d) MnCl MnCl Cl → REDOX REACTIONS Ans (a) Sol. a. Oxidation states of Ca and C are +2 and +4, respectively, in both reactant and product; hence, not redox. b. 4e O 2O → (Reduction) H 2H 2e → (Oxidation) Hence, redox c. Na Na e → (Reduction) d. Mn Cl Mn Cl Cl → Mn is getting reduced from +3 to +2. Cl is getting oxidised from 1 to 0.