Chapter 19, Problem 19.37CP

Interpretation Introduction

(a)

Interpretation:

Balanced equation for each cell reaction should be written.

Concept introduction:

A galvanic cell can be represented using a shorthand notation. For example, a redox reaction and its cell notation is given below.

${\text{Zn(s) + Cu}}^{2+}\text{(aq) }\to {\text{ Zn}}^{2+}\text{(aq) + Cu(s)}$

${\text{Zn(s) | Zn}}^{2+}{\text{(aq) || Cu}}^{2+}\text{(aq) | Cu(s)}$

The single vertical line (|) indicates the phase boundary. The double vertical line (||) indicates the salt bridge. The shorthand notation for anode half-cell is written on left side of the double vertical line and notation for cathode half-cell is written on the right side of the double vertical line. The electrodes are indicated in the two extreme ends of the cell notation. Always reactants in each half-cell is written first and followed by products. The electrons move through the external circuit from left to right (from anode to cathode).

Interpretation Introduction

(b)

Interpretation:

Each cell should be sketched and anode and cathode should be labeled. The direction of electron and ion flow should be indicated.

Concept introduction:

Anode is the electrode where oxidation takes place and electrons are produced. Anode has a negative sign in galvanic cell. Cathode is the electrode where reduction takes place and electrons are consumed. Cathode has a positive sign.

Anions move form cathode compartment towards anode compartment while cations migrate from the anode compartment towards the cathode compartment.

Interpretation Introduction

(c)

Interpretation:

Which cell has the largest and which has the smallest cell potential should be deduced.

Concept introduction:

The Nernst equation allows to calculate cell potential at non-standard conditions.

$E=E^0-\frac{0.0592\text{ V}}{n}\log Q$

E − non-standard cell potential

E⁰ − standard cell potential

n − number of electrons passed through the cell

Q − reaction quotient

The standard cell potential of overall reaction is given by the sum of the standard half-cell potentials for oxidation and reduction.

${\text{E}}_{overall}^0={\text{E}}_{ox}^0+{\text{ E}}_{red}^0$