Electrode Potentials And Cells

Question 1

How is a potential difference created in electrode cells?

Answer 1

• Redox reactions are used as the electron transfer between products creates a flow of electrons.
• Flow of charged particles is an electrical current which flows between electrodes in the cells.
• A potential difference is produced between the two electrodes which can be measured.

Question 2

What is a salt bridge?

Answer 2

A tube of unreactive ions that can move between the solutions to carry the flow of charge but will not interfere with the reaction.

Question 3

What are the conditions and potential of the S.H.E?

Answer 3

• Conc of H+ = 1 mol dm-3
• Temp = 298k
• Pressure = 100kpa
• 0.00V

Question 4

What are the rules of conventional cell representation?

Answer 4

• The half cell with the most negative potential goes in the left
• Most oxidised species from each half cell goes next to the salt bridge
• A slat bridge is shown using a double line
• Always include state symbols

Question 5

Are negative potentials oxidised or reduced?

Answer 5

• Oxidised and will lose electrons

Question 6

Are positive potentials oxidised or reduced?

Answer 6

• Reduced and will gain electrons

Question 7

How do you calculate cell EMF?

Answer 7

• Ecell = Erhs - Elhs
• Ecell = Ered - Eox
  = correct cell diagrams should give a positive value

Question 8

What is the anti-clockwise rule?

Answer 8

• Write the most negative EMF out of the pair on top
• Draw anti-clockwise arrows around the reactions
• Balance the electrons on both sides of the reaction
• Write out the cell reaction