Question

Which of the following reactions is a redox reaction

• A. $CaCO _{3}+2 HCl \longrightarrow CaCl _{2}+ H _{2} O + CO _{2}$
• B. $AgNO _{3}+ KI \longrightarrow Agl + KNO _{3}$
• C. $Cl _{2}+2 Br ^{-} \longrightarrow Br _{2}+2 Cl ^{-}$
• D. $BaCl _{2}+ SO _{4}^{2-} \longrightarrow BaSO _{4}+2 Cl ^{-}$

Answer 1

The Correct Option is C

$Cl _{2}+2 Br ^{-} \longrightarrow Br _{2}+ Cl ^{-}$ is a redox reaction as it involves both oxidation and reduction reactions simultaneously.



In the other options (a), (b) and (d) there is no change in oxidation state of any atom, hence these are not redox reaction.

(A) $\overset{+1}{Ag}\overset{+5}{N}\overset{-2}{O_3} + \overset{+1}{K} \overset{-1}{I} \longrightarrow \overset{+1}{Ag} \overset{-1}{I} + \overset{+1}{K} \overset{+5}{N} \overset{-2}{O_3}$

(B) $\overset{+2}{Ba}\overset{-2}{Cl_2} + SO^{2-}{4} \longrightarrow \overset{+2}{Ba} S \overset{-2}{O_4} + 2\,Cl^-$

(C) $\overset{+2}{Ca}\overset{+4}{C}\overset{-2}{O_3} + 2 \overset{+1}{H} \,C\overset{-1}{I} \longrightarrow \overset{+2}{Ca} C \overset{-1}{I_2} + \overset{-1}{Ca} C \overset{-1}{l_2} + \overset{-1}{H_2}\overset{-2}{O} + \overset{+4}{C} \overset{-2}{O_2}$