Question

Which metal(s) can be oxidized with a Pb2+ solution but not with a Cd2+ solution? (Hint: The reactions are occurring under standard conditions.)
A. Cr
B. Ni
C. Zn
D. Sn

Answer 1

Answer:

B. Ni

D. Sn

Explanation:

Electrode Potential is the potential difference set up between an element and a solution of its ion. It is a measure of the tendency of an element to form ions.

The electrode potentials vary from one metal ion or metal system to another and the value depends on:

concentration of ions in the solution

the temperature at which the measurement is made , and

the overall energy change.

When two half-cells are joined together through a salt bridge, the e.m.f (electromotive force) of the cell formed is the algebraic difference between the two electrode potentials.

However, the set up in which chemical energy is converted to electrical energy is known as an Electrochemical cell. It consists of two half cells ;

an oxidation half-cell reaction  

a reduction  half cell reaction.

From the information given:

the standard reduction potential for each metal under standard conditions in the electrochemical series is as follows :

$E^0 _{Pb} = -0.126 \ V$

$E^0 _{Cr} = - 0.74 \ V$

$E^0 _{Ni} =- 0.23 \ V$

$E^0 _{Zn} =- 0.76 \ V$

$E^0 _{Sn} = -0.13 \ V$

$E^0 _{Cd} = - 0.40 \ V$

We will realize that  Ni and Sn have reduction values in between Pb and Cd.

Thus , Ni can be oxidized by Pb2+  solution  but not with a Cd2+ solution