Question

Arrange the following metals in which they displace each other from the solutions of their salts in decreasing order:$Al,Cu,Fe,Mg$ and $Zn$
$E_{A{l}^3+/Al}^0+-1.66V,E_{C{u}^2+/Cu}^0=+0.34V$,
$E_{F{e}^2+/Fe}^0=-0.44V,E_{M{g}^2+/Mg}^0=-1.40V$
$E_{Z{n}^2+/Zn}^0=-0.76V$

• A. $Cu,Fe,Zn,Al,Mg$
• B. $Fe,Zn,Cu,Al,Mg$
• C. $Mg,Cu,Fe,Zn,Al$
• D. $Mg,Al,Zn,Fe,Cu$

Answer 1

Answer: (D)

$Mg,Al,Zn,Fe,Cu$

Reduction potential for $Al,Cu,Fe,Mg$ and $Zn$ ions is given as:
$E_{A{l}^{3+}/Al}^0$ = -1.66 V , $E_{C{u}^{2+}/Cu}^0$ = +0.34 V,
$E_{F{e}^{2+}/Fe}^0$ = -0.44 V , $E_{M{g}^{2+}/Mg}^0$ = -1.40 V, $E_{Z{n}^{2+}/Zn}^0$ = -0.76 V

Increasing order of reduction potential is therefore:

$M{g}^{2+}<A{l}^{3+}<Z{n}^{2+}<F{e}^{2+}<C{u}^{2+}$

Thus it is the ease of gaining electron by the salt of metal ions and get reduced to respective metal.

Hence $Mg$ metal can displace all the other ions from their solutions as others have higher reduction potential than $Mg$. $Al$ can displace all metal ions except $Mg,Zn$ can displace $Fe$ and $Cu$ from their salt solutions. $Fe$ can displace $Cu$ only from its salt and copper will not displace any ion from its solution.

Therefore decreasing order of metals in which they displace other metal ions from the solutions of their salts is:

$Mg>Al>Zn>Fe>Cu$