4C - Electrode potentials and cells

Whats an electrochemical cell made of?

Two different metals dipped in salt solutions of their own ions and connected by a wire and salt bridge (redox process)

How do electrons flow in an electrochemical cell?

From the most reactive metal to the least

What is the cell potential?

The voltage between the two half cells

What is need if the half cell only contains two aqueous ions?

Platinum electrode

What do electrochemical cells look like?

What electrode potential do you always put on the left?

Lowest (left lowest)

What is the equation for calculating the cell potential?

E0 cell = right hand side - left hand cell (more negative - more positive) (reduced - oxidised)

What is the anode?

Where oxidation occurs (gains electrons)

What is the cathode?

Where reduction occurs (loses electrons)

What format are electrode potentials always in?

Reduction reactions

What is the standard hydrogen electrode?

The electrode potential that all the others are compared to

What are the standard conditions for a hydrogen electrode?

• Concentration of 1moldm-3

• Temperature of 298K

• Pressure of 100kPa

What is the electrochemical series?

List of electrode potential for different electrochemical half-cells

What does it mean if a reaction is not feasible?

It will not occur

When are some cells non-rechargeable?

Irreversible reactions used

What makes a cell rechargeable?

Reversible reactions

What is the overall reaction in a alkaline fuel cell?

2H+ + O2 → 2H2O

What is the reaction at the negative electrode of the alkaline fuel cell?

H2 + 2OH- → 2H20 + 2e-

What is the reaction at the positive electrode of the alkaline fuel cell?

O2 + 2H2O + 4e- → 4OH-

What are the pros of a fuel cell?

• More efficient

• Only waste product is water

• Don’t need to be reacharged

What are the cons of a fuel cell?

• Energy needed to supply hydrogen

• Hydrogen is highly flammable

• Infrastructure for hydrogen fuel cars doesn’t exist