Electrode potentials

Question 1

What are electrochemical cells made from?

Answer 1

Two different metals dipped in salt solutions of their own ions and connected by a wire

Question 2

What two reactions take place within an electrochemical cell?

Answer 2

Oxidation

Reduction

Question 3

What would a copper electrode be dipped in?

Answer 3

solution of Cu2+ ions

Question 4

What would a zinc electrode be dipped in?

Answer 4

solution of Zn2+ ions

Question 5

Which electrode is oxidised?

Answer 5

The metal which loses electrons easiest

Question 6

What is a half cell?

Answer 6

One electrode dipped in a solution of its own ions

Question 7

What flows through between the two electrodes?

Answer 7

Electrons through a wire on the external circuit

Question 8

What is the cell potential or EMF? What is it measured by?

Answer 8

The voltage between the two-half cells

Voltmeter

Question 9

What is a salt bridge?

Answer 9

Connects the two solutions

Allows ions to flow between the two half cells, balances out the charges and completes the circuit

Question 10

What is an example of a salt bridge?

Answer 10

Strip of paper soaked in KNO3 (aq)

Question 11

Why is platinum used when you have two half cells involving two solutions of the same element eg. Fe 2+ and Fe3+?

Answer 11

It is inert and conducts electricity

Question 12

What type of reactions occur at each electrode?

Answer 12

Reversible

Question 13

What are electrode potentials used for?

Answer 13

To measure how easily a metal is oxidised

Question 14

What type of electrode potential will a metal thats easily oxidised have?

Answer 14

Very negative electrode potential

Question 15

What type of electrode potential will a metal that is harder to oxidise have?

Answer 15

less negative or positive electrode potential

Question 16

What are the stages in drawing electrochemical cells?

Answer 16

1) The left hand equation is the oxidation reaction and the right hand equation is the reduction reaction
2) Write out the reactants and products of the oxidation reaction and then the reactants and products of the reduction reaction.
3) the reduced forms go on the outside of the cell diagram and the oxidised forms go on the inside
4) Draw two vertical lines in the middle of the two half cells to represent the salt bridge
5) Draw one vertical line between any reagents the are in different phases and a comma between any that are the same
6) If you have any half cells with a separate electrode eg. Pt, put that on the outside and separate from the half cell with a vertical line

Question 17

How do you calculate the electrode potential of a cell?

Answer 17

Electrode potential of the right hand side - electrode potential on the left hand side

Question 18

Why will the cell potential always be positive?

Answer 18

You are taking away the more negative from the more positive value