The change in colour of the moist litmus paper in the given set up is due toi. presence of acidii. presence of baseiii. presence of H⁺(aq) in the solutioniv. presence of Litmus which acts as an indicator(a) i and ii(b) Only ii(c) Only iii(d) Only iv.12 In the redox reactionMnO2 + 4HCl → MnCl2 + 2H2O + Cl2(a) MnO2 is reduced to MnCl2& HCl is oxidized to H2O(b) MnO2 is reduced to MnCl2& HCl is oxidized to Cl21

The change in color of the moist litmus paper in the given setup is due to the presence of an acid or a base. Litmus paper is a pH indicator used to test materials for acidity. Blue litmus paper turns red under acidic conditions and red litmus paper turns blue under basic or alkaline conditions. Therefore, the correct answer is (a) i and ii.

In the redox reaction MnO2 + 4HCl → MnCl2 + 2H2O + Cl2, MnO2 is reduced to MnCl2 and HCl is oxidized to Cl2. In a redox reaction, one reactant is reduced (gains electrons) and another is oxidized (loses electrons). Here, MnO2 is reduced (its oxidation state decreases from +4 in MnO2 to +2 in MnCl2) and HCl is oxidized (its oxidation state increases from -1 in HCl to 0 in Cl2). Therefore, the correct answer is (b) MnO2 is reduced to MnCl2 & HCl is oxidized to Cl2.