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# Which of the following reactions are not possible ?

$\begin{array}{1 1}(a)\;Cl_2+KBr\rightarrow KCl+Br_2\\(b)\;Br_2+KI\rightarrow KBr+I_2\\(c)\;Zn+H^+\rightarrow Zn^{+2}+H_2\\(d)\;Cu+H^+\rightarrow Cu^{+2}+H_2\end{array}$

By electro chemical series $E^o_{Cl_2/Cl^-} > E^o_{Br_2/Br^-} > E^o_{I_2/I^-}$
So (a) & (b) are possible.
$E^o_{Cu^{+2}/Cu} > E^o_{H^+/H_2} > E^o_{Zn^{+2}/Zn}$
So (c) is possible and (d) is not possible.
Hence (d) is the correct answer.