Electrode potentials and cells (KEY MEMORY)

Question 1

What are the standard conditions of the SHE

Answer 1

H2(g) in at 298K, 100kPa
1moldm-3 of H+ ions
Pt electrode

Question 2

What is the electrochemical series

Answer 2

A list of half cell reactions and their E°

Question 3

In an electrochemical series, which species is the strongest oxidising agent

Answer 3

The most POSITIVE species on the LEFT hand side
OAPL (Opal - this acronym is a gem)

Question 4

In an electrochemical series, which species is the strongest reducing agent

Answer 4

The most NEGATIVE species on the RIGHT hand side
RANR

Question 5

What does a negative E°cell mean in terms of feasibility

Answer 5

Reaction not feasible (requires energy)

Question 6

What are the components of a lithium ion battery

Answer 6

Electrode A - Lithium cobalt oxide (LiCoO2)
Electrode B - Graphite (C)
Electrolyte - Lithium salt dissolved in an organic solvent

Question 7

What is the purpose of the electrolyte in a battery

Answer 7

Acts as a conductive pathway for ions to move from one electrode to another

Question 8

What is the equation for the reaction occurring at the anode in a lithium ion battery

Answer 8

Li → Li+ + e–

Question 9

What is the equation for the reaction occurring at the cathode in a lithium ion battery

Answer 9

Li+ + CoO2 + e– → Li+ [CoO2]–

Question 10

What is the overall equation of discharge of a lithium ion battery

Answer 10

(Combining two half equation)
Li + CoO2 <—> Li+[CoO2]-

Question 11

What is the equation of recharge of a battery

Answer 11

The opposite of discharge equation

Question 12

Why are lithium ion battery good at powering electronics

Answer 12

Significant potential difference
Need a lot of power for phones laptops etc

Question 13

What is the main difference between a fuel cell and a battery

Answer 13

Electricity is generated by a continuous external supply of chemicals rather than a ready store like in batteries

Question 14

What is the middle part of a hydrogen oxygen fuel cell

Answer 14

The electrolyte

Question 15

What is the electrolyte in a hydrogen oxygen fuel cell

Answer 15

KOH solution

Question 16

What is the purpose of the electrolyte in a hydrogen oxygen fuel cell

Answer 16

Carries OH- ions from the cathode to the anode

Question 17

Which way do electrons flow in a hydrogen oxygen fuel cell

Answer 17

From the anode to the cathode

Question 18

What is the only product in a hydrogen oxygen fuel cell

Answer 18

Water

Question 19

What are platinum electrodes lined with in a hydrogen oxygen fuel cell

Answer 19

Ion exchange membrane

Question 20

What is the purpose of the ion exchange membrane on the platinum electrode in a hydrogen oxygen fuel cell

Answer 20

Allow OH- ions to pass through but not hydrogen and oxygen gas

Question 21

What is the equation for the reaction at the anode in a hydrogen oxygen fuel cell in basic conditions

Answer 21

H2(g) + 2OH-(aq) –> 2H2O(l) + 2e-

Question 22

What is the equation for the reaction at the cathode in a hydrogen oxygen fuel cell in basic conditions

Answer 22

02(g) + 2H2O(l) + 4e- —-> 4OH-(aq)

Question 23

What is the overall reaction occurring in a hydrogen oxygen fuel cell (either acidic or basic)

Answer 23

2H2(g) + O2(g) —> 2H2O(g)

Question 24

What is the equation for the reaction at the cathode in a hydrogen oxygen fuel cell in acidic conditions

Answer 24

1/2O2 + 2H+ + 2e- —> H2O

Question 25

What is the equation for the reaction at the anode in a hydrogen oxygen fuel cell in acidic conditions

Answer 25

H2 —> 2H+ +2e-

Question 26

Sketch a hydrogen oxygen fuel cell stating what occurs at each stage

Answer 26

1. Hydrogen feed: Hydrogen is fed in here. It reacts with OH- ions in solution in 9 (more on this later). The reaction that occurs is- 2H2(g) + 4OH (aq) → 4H2O(l) + 4e- 2. Flow of electrons: Electrons produced in reaction 1 travel through a platinum electrode. Platinum is a good conductor of electricity but inert. 3. Component: The flow of electrons is used to power something. E.g. a car 4. Oxygen Feed: Oxygen is fed in here. It reacts with water and the 4 electrons made from step 1 to make OH ions. The reaction that occurs is- 02(g) + 2H2O(l) + 4e- → 40H- (aq) 5. Negative electrode (cathode): Electrons flow to the negative electrode which is made from platinum. 6. Electrolyte: The electrolyte is made from KOH solution. It carries the OH ions from the cathode to the anode. 7. Positive electrode (anode): Electrons flow from the positive electrode which is made from platinum. 8. Water emitted: The product of the reaction in step 1 is released into the surroundings 9. Movement of OH ions: OH ions produced from reaction 4 are carried towards the anode via the electrolyte.

Question 27

What is the equation of the reaction occurring at the anode when measuring electrode potentials using the SHE

Answer 27

H2 ---> 2H+ + 2e-

Question 28

What is an electrochemical series

Answer 28

A list of half cell reactions and their Eᵒ values in numerical order

Question 29

Why is the Ecell of an acidic and basic hydrogen oxygen fuel cell the same

Answer 29

Same overall reaction

Question 30

Why do fuel cells not need to be recharged

Answer 30

CONTINUOUS supply of fuel