SSC GD 2023 PYQ — Question 27

The correct answer is option 3 i.e. $MnO_2+ 4HCl → MnCl_2 + 2H_2O + Cl_2$.

A redox reaction involves the transfer of electrons, where one species is oxidized (loses electrons) and another is reduced (gains electrons). Let's identify the redox reaction from the options:

2Pb(NO₃)₂ (s) → Heat → 2PbO(s) + 4NO₂ (g) + O₂ (g): This is a thermal decomposition reaction, not a redox reaction.

CaCO₃(s) → Heat → CaO(s) + CO₂(g): This is a decomposition reaction, not a redox reaction.

MnO₂ + 4HCl → MnCl₂ + 2H₂O + Cl₂: This is a redox reaction. Manganese (Mn) is reduced from +4 in MnO₂ to +2 in MnCl₂, while chlorine (Cl) is oxidized from -1 in HCl to 0 in Cl₂.

Pb(s) + CuCl₂(aq) → PbCl₂(aq) + Cu(s): This is also a redox reaction. Lead (Pb) is oxidized from 0 to +2, and copper (Cu) is reduced from +2 to 0.

So, the correct redox reactions are MnO₂ + 4HCl → MnCl₂ + 2H₂O + Cl₂ and Pb(s) + CuCl₂(aq) → PbCl₂(aq) + Cu(s).