Circle only those of the following reactions that are redox reactions:

K2CrO4 + BaCl2? BaCrO4 + 2 KCl

Cu+S? CuS

AgNO3 + HCl? HNO3 + AgCl

2 Na + 2 H2O? 2 NaOH + H2

MgBr2 + 2 NaF? MgF2 + 2 NaBr

2 CO + O2? 2 CO2

SO2 + H2O? H2SO3

Answer: options B, D and F

Explanation:

Since redox reactions are those which involves both oxidation and reduction

In B, Cu is oxidized and S gets reduced

D, Na gets oxidized and hydrogen gets reduced

F, carbon gets oxidized and Oxygen gets reduced

In g, there is no change in oxidation no of s in both product and Reactants is same + 4

Similarly in the case of Ag and Mg.