Question

Which balanced equation represents an oxidation-reduction reaction?

(1) BaCl2 + Na2SO4==>BaSO4 + 2NaCl
(2) C+H2O ==>CO + H2
(3) CaCO3==>CaO + CO2
(4) Mg(OH)2 + 2HNO3==>Mg(NO3)2 + 2H2O

Answer 1

The answer is (2). The oxidation-reduction reaction means that there is electrons transfer in the reaction. So there is valence change of at least two elements evolving in the reaction.

Answer 2

Correct Answer: option 2 i.e. (2) C+H2O ==>CO + H2

Reason:
Reaction is said to be oxidation-reduction (redox) type, when one species undergoes oxidation, while other species undergoes reduction. In present case, during the course of reaction, carbon is oxidized from '0' to '+2'. On other hand, hydrogen is reduced from '+1' to '0'.