[3.1.11] Electrode Potentials & Electrochemical Cells

Question 1

What is an electrochemical cell?

Answer 1

Question 2

Using the image below, describe why a voltage forms in this cell.

Answer 2

Question 3

Why do we use a high-resistance voltmeter to measure potential differences?

Answer 3

Question 4

What is a salt bridge?

What is it made of and what is one of its key properties?

Why isn’t a wire used instead of a salt bridge?

Answer 4

Question 5

If in the image below the voltmeter were to be removed, what would happen?

Answer 5

Question 6

Use a cell diagram to represent the electrochemical cell shown in the image below.

Answer 6

Question 7

If a system does not include a metal that can act as an electrode, what is used instead? How does it work and why is it used?

Answer 7

Question 8

Use a cell diagram to represent the reaction occurring at a half-cell below:

Answer 8

Question 9

Use a cell diagram to represent the reaction occurring at a half-cell below:

Answer 9

Question 10

Use a cell diagram to represent the reaction occurring at a half-cell below:

Answer 10

Question 11

Use a cell diagram to represent the reaction occurring at a half-cell below:

Answer 11

Question 12

How do we measure the electrode potential of a cell?

Answer 12

Question 13

The potential of all electrodes is measured by comparing
their potential to that of the standard hydrogen electrode.

What are the conditions of the SHE, and why are these conditions needed?

Answer 13

Question 14

How is the SHE represented in a cell diagram?

Answer 14

Question 15

What is the hydrogen electrode equilibrium?

Answer 15

Question 16

When an electrode system is connected to the SHE and standard conditions apply, what is the potential difference measured called?

Answer 16

• The standard electrode potential.

Question 17

How do you calculate the EMF of a cell?

Answer 17

Question 18

Calculate the EMF of the cell below:

Answer 18

Question 19

What will the more negative half-cell always do?

What will the more positive half-cell always do?

Knowing this, what equation can you use to calculate the EMF?

Answer 19

• The more negative half cell will always oxidise.
• The more positive half cell will always reduce.

Question 20

Using the E° values of the equations below, predict the direction of the redox reactions.

Answer 20

Question 21

Using the E° values of the equations below, predict the direction of the redox reactions.

Answer 21

Question 22

Where will the most powerful reducing agents and most powerful oxidising agents be found on an electrochemical series?

Answer 22

Question 23

Using electrode data below explain why fluorine reacts with water.

Write an equation for the reaction that occurs and a conventional cell diagram too.

Answer 23

Question 24

Use data from the table below to explain why chlorine should undergo a redox reaction with water.

Write an equation for this reaction.

Answer 24

Question 25

Answer 25

Question 26

Use the half equations below to explain in terms of oxidation state what happens to hydrogen peroxide when it is reduced.

Answer 26

Question 27

What is the effect of concentration on Ecell?

Answer 27

Question 28

What is the effect of temperature on Ecell?

Answer 28

Question 29

What makes a cell non-rechargeable?

Answer 29

- When the reactions that occur within them are **non-reversible**.

Question 30

Using the E° values below and the half-equations, write the overall reaction, calculate the EMF and show the conventional cell diagram of the lithium-manganese dioxide cell.

Answer 30

Question 31

Using the E° values below and the half-equations, write the overall reaction that occurs when the lead acid cell discharges. Calculate its EMF too.

Answer 31

Question 32

Using the E° values below and the half-equations, write the overall reaction when the nickel-cadmium cell discharges and recharges. Calculate its EMF too.

Answer 32

Question 33

What are the simplified electrode reactions in a lithium cell?

Answer 33

Question 34

In a lithium cell, at the positive electrode, there is an E° value of +0.6V and at the negative electrode, there is an E° value of -3.0V. With the aid of these E° values, write the overall reaction that occurs when the lithium cell discharges and recharges. Calculate its EMF and show the conventional cell diagram.

Answer 34

Question 35

What is a fuel cell?

Answer 35

Question 36

Why don't fuel cells need to be recharged?

Answer 36

Question 37

What are the electrode reactions in an alkaline hydrogen-oxygen fuel cell?

Answer 37

Question 38

What are the advantages of fuel cells?

Answer 38

Question 39

What are the limitations of fuel cells?

Answer 39

Question 40

What is an electrochemical series?

Answer 40

Question 41

Using the half-equations below, which reactants would you have to increase to increase Ecell?

Answer 41

Question 42

What is Ecell a measure of?

Answer 42

Question 43

What can electrochemical cells be used for? What types are there?

Answer 43

Question 44

Using the half-equations below and their E values, write the overall equation for the reaction that occurs and calculate the EMF value, too.

Answer 44