Electrode Potentials

Question 1

What is an oxidising agent?

Answer 1

Something that oxidises another species, therefore it is reduced itself

Question 2

What is a reducing agent?

Answer 2

Something that reduces another species, therefore it is oxidised itself

Question 3

What are the different types of half cell?

Answer 3

Metal / Metal ion

Ion / Ion

Gas / Ion

Question 4

Describe the structure of a Metal/ Metal ion half cell

Answer 4

A metal rod is dipped in a beaker containing its aqueous metal ions

e.g Cu metal rod dipped in a solution of Cu2+ ions

Question 5

Describe the structure of an ion / ion half cell

Answer 5

An inert Platinum electrode is dipped in a solution containing 2 different oxidation states of a metal

e.g a solution of Fe2+ and Fe3+ aqueous ions

Question 6

Which electrode is oxidised, the most or least reactive?

Answer 6

Most reactive is oxidised

so the least reactive is reduced

Question 7

How would you measure the Standard Electrode Potential of a half cell?

Answer 7

Compare it to a standard Hydrogen Half cell

A hydrogen cell is 0V,
The difference is the standard electrode potential of the half cell you want to measure

Question 8

What conditions must you measure standard electrode potentials under?

Answer 8

1 moldm-3 solutions

298K

100 kPa (1 bar)

Question 9

Describe the structure of a standard hydrogen half cell?

Answer 9

Gas tube with holes in the bottom to let H2 bubble out

An inert Platinum electrode

A solution of 1 moldm-3 H+ ions (acid)

Question 10

In terms of electrons, what will happen to a half cell with a more -ve E value?

Answer 10

Greater tendency to LOSE electrons and undergo oxidation

Question 11

In terms of electrons, what will happen to a half cell with a more +ve E value?

Answer 11

Greater tendency to GAIN electrons and be reduced

Question 12

How do you work out the cell potential from 2 half cell potential values?

Answer 12

You minus the more -ve value from the more +ve value