Electrode Potentials

Question 1

If it is more reactive where with it go

Answer 1

To the anode
The more negative the E value is the more reactive, so more easily it goes under oxidation, so it gives up its electrons
AO let’s go
Anode is oxidisation

Question 2

More positive E value will go to anode/cathode?

Answer 2

Cathode
More positive E value the more it gains electrons, so the more reductive.
CR
Christiano Renaldo
Cathode is reduction

Question 3

Calculate emf value

Answer 3

Right - left
More positive - more negative

Question 4

Units of emf value

Answer 4

Volts

Question 5

What is the salt bridge for

Answer 5

Allows ions to move across

Question 6

Standard condition of Electrochemical cell

Answer 6

Conc - 1 mol dm-3 but be careful if H2SO4 used as this needs 0.5 mol em-3 as there are 2H+ this equals to 1 Mol dm-3
Temp - 298K
Pressure - 100kPa

Question 7

Why is Hydrogen 0V

Answer 7

By definition

Everything is relative to hydrogen

Question 8

Why is Pt used sometimes

Answer 8

Inert metal that can conduct electricity for electrons to move
I think usually used when reactions only contain aqueous substances - double check

Question 9

Electrode potential equation

Answer 9

R O || O R
Only compounds going through redox is put into this
Solid, aqueous || aqueous, solid
Left - anode
Right - cathode
This is because you have to lose electrons before you gain electrons so oxidation comes before reduction

Question 10

How does changing the concentration of Zn2+ affect E value
Zn2+ + 2e- <—-> Zn
-0.76V

Answer 10

Increasing Zn2+ will shift equilibrium to the right towards Zn
This will increase the Zn E value making it less negative so the overall E value will decrease (between Zn and another ion)
- _________+
-0.76 —— -0.50 - this makes Zn E value less negative

Looking at Zn and another ion eg Cu which has E value +0.34V
Original E value = 0.34 + 0.76 = 1.1V
New E value = 0.34 + 0.50 = 0.84V so overall E value decreases.

Vice versa
Increase Zn equilibrium shifts to the left towards Zn2+
Makes Zn E value more negative to overall E value will Increase.

Question 11

Which is at the anode/cathode
What is the emf value
What is the sentence used at the end of this
Reduction equations:
Zn2+ + 2e- <—-> Zn / E value = -0.76V
Cu2+ + 2e- <—-> Cu / E value = +0.34V

Answer 11

1. Anode
   - Zn <—> Zn2+ + 2e- the equation flips as oxidation occurs here AO

Cathode
- Cu2+ +2e- <—> Cu the equation remains as reduction occurs here CR

2. emf = 1.1V
3. E value (Cu2+/Cu) > E value (Zn2+/Zn) so Cu2+ gains electrons from Zn

Question 12

Different type of cells

Answer 12

1. Non-rechargeable
2. Rechargeable
3. Fuel cells

Question 13

Lithium cell equation

Answer 13

Question 14

What type of cell is a lithium cell

Answer 14

Rechargeable

Question 15

Fuel cells: Hydrogen-Oxygen fuel cell
The equations involved

Answer 15

Question 16

Pros and cons of cells

Answer 16