3.1 - Redox and Standard Electrode Potential Flashcards

1
Q

Define oxidation in terms of electron transfer

A

Loss of electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Define reduction in terms of electron transfer

A

Gain of electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is a redox reaction?

A

A redox reaction is a reaction in which oxidation and reduction occur on different species simultaneously.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is standard electrode potential?

A

Standard electrode potential is the potential across the electrodes when a redox system is connected to a hydrogen half-cell under standard conditions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What conditions are required for measuring the standard electrode potential?

A
  • 298 K temperature
  • 100 kPa pressure
  • 1.00 mol dm-3 concentration of ions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Why is a hydrogen half-cell needed as a reference?

A

The hydrogen half cell is used to allow for easy comparison between the electrode potential of different elements. The standard electrode potential for hydrogen is assumed to be zero volts at any temperature.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the experimental setup to calculate the standard electrode potential for zinc?

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Why must metal electrodes be cleaned with sandpaper before creating an electrochemical cell?

A

To remove any metal oxide that has formed on the surface and improve electrical conductivity.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe the movement of electrons in an electrochemical cell

A

Electrons flow through the wire from the positive electrode to the negative electrode.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Why is a salt bridge used in an electrochemical cell?

A
  • To maintain the charge balance and complete the circuit.
  • Negative electrons are moving from one half cell to another. Without the salt bridge, positive charge would build up in the half cell containing the anode and negative charge would build up in the half cell containing the cathode. This would cause the reaction to stop.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Why must an inert salt be used in the salt bridge?

A

The salt must be inert so that it doesn’t react with the solutions and alter the ion concentrations. If a reactive salt was used, the cell potential would change.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What moves across the salt bridge?

A

Ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

For what range of cell potential values is a process feasible?

A

Cell potential must be greater than 0.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How can cell potential be calculated?

A

Eθcell =
Eθ(positive terminal) - Eθ(negative terminal)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Why might theoretical cell potential values be different to values obtained experimentally?

A

Conditions may be non-standard.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Draw a diagram showing a standard Fe2+/Fe3+ cell

A
17
Q

A cell is made up of the following half cells: Ag+(aq) + e- ⇌ Ag(s) Eθ = +0.80V Cu2+(aq) + 2e- ⇌ Cu(s) Eθ = +0.34V Write the overall cell equation and calculate the standard cell potential

A

Write the overall cell equation and calculate the standard cell potential
2Ag+(aq) + Cu(s) → Ag(s) + Cu2+(aq) Eθcell = +0.80 - (+0.34) = 0.46V

18
Q

In an electrochemical cell, is the more negative half cell oxidised or reduced?

A

Oxidised

19
Q

What is a fuel cell?

A

A cell that continually produces a voltage as long as it is supplied with oxygen and a fuel (like hydrogen).

20
Q

What is the only product of a hydrogen-oxygen fuel cell?

A

Water

21
Q

How does a hydrogen-oxygen fuel cell work?

A

Hydrogen and oxygen are pumped through porous electrodes. The electrolyte is often an acid such as phosphoric acid.
Hydrogen and oxygen react, producing energy and water.

22
Q

What are the two half equations taking place in a hydrogen-oxygen fuel cell?

A

2H2+ 4OH- ⇌ 4H2O + 4e- O2 + 2H2O + 4e- ⇌ 4OH-

23
Q

Write an equation for the overall reaction that takes place in a hydrogen-oxygen fuel cell

A

2H2 + O2 → 2H2O

24
Q

What are the advantages of using fuel cells?

A
  • No pollution.
  • They produce more energy than an
    alternative fuel like petrol.
  • The process is continuous as long as the fuel is supplied.
25
Q

What are the disadvantages of using fuel cells?

A
  • Materials used to make them are expensive.
  • High pressure tanks are required to store oxygen and fuels like hydrogen.
  • Hydrogen is expensive and hard to store.
  • Efficiency is affected by temperature.