Question

Which of the following is not an example of redox reaction?

• A. $CuO+H_2\to Cu+H_{2}O$
• B. $F{e}_2{O}_3+3CO\to 2Fe+3C{O}_2$
• C. $2K+F_2\to 2KF$
• D. $BaC{l}_2+H_{2}S{O}_4\to BaS{O}_4+2HCl$

Answer 1

The correct option is D $BaC{l}_2+H_{2}S{O}_4\to BaS{O}_4+2HCl$

(a) $\stackrel{+2}{C}uO+{\stackrel{0}{H}}_2\to \stackrel{0}{C}u+{\stackrel{+1}{H}}_{2}O$
As oxidation number of $Cu$ is changed from $+2$ to $0$ and that of $H$ is changed from $0$ to $+1$, this is an example of redox reaction.
(b) $\stackrel{+3}{F}{e}_2{O}_3+3\stackrel{+2}{C}O\to 2\stackrel{0}{F}e+3\stackrel{+4}{C}{O}_2$
As oxidation number of $Fe$ changes from $+3$ to $0$ and that of $C$ changes from $+2$ to $+4$, this is an example of redox reaction.
(c) $2\stackrel{0}{K}+{\stackrel{0}{F}}_2\to 2\stackrel{+1}{K}\stackrel{-1}{F}$
As oxidation number of $K$ changes from $0$ to $+1$ and that of $F$ changes from $0$ to $-1$, this is an example of redox reaction.
(d) $\stackrel{+2}{B}aC{l}_2+H_2\stackrel{+6}{S}{O}_4\to \stackrel{+2}{B}a\stackrel{+6}{S}{O}_4+2\stackrel{+1}{H}Cl$
Oxidation number of all the elements remains unchanged. Hence, this is not an example of redox reaction.