Question

Based on the following reactions, arrange the metals in increasing order of their reduction potentials.
$Zn+C{u}^{2+}\to Z{n}^{2+}+Cu$
$Mg+Z{n}^{2+}\to M{g}^{2+}+Zn$
$Cu+2A{g}^{+}\to C{u}^{2+}+2Ag$

• A. $Mg>Zn>Cu>Ag$
• B. $Mg<Zn<Cu<Ag$
• C. $Zn<Cu<Ag<Mg$
• D. $Mg>Cu>Zn>Ag$

Answer 1

Answer: (B)

$Mg<Zn<Cu<Ag$

Given reactions are:

i) $Zn+C{u}^{2+}\to Z{n}^{2+}+Cu$ ;

Since $C{u}^{2+}$ gains electron and gets reduced in the presence of $Zn$, thus $Cu$ will have higher reduction potential than $Zn$ ($Zn<Cu$)

ii) $Mg+Z{n}^{2+}\to M{g}^{2+}+Zn$;

Since $Z{n}^{2+}$ gains electron and gets reduced in the presence of $Mg$, thus $Zn$ will have higher reduction potential than $Mg$ ($Mg<Zn$)

iii) $Cu+2A{g}^{+}\to C{u}^{2+}+2Ag$

Since $A{g}^{+}$ gains electron and gets reduced in the presence of $Cu$, thus $Ag$ will have higher reduction potential than $Cu$ ($Cu<Ag$)

Using the above order of reduction potential we get:

$Mg<Zn<Cu<Ag$ as the increasing order of their reduction potentials of given metals.