electrode potentials exam q's

Question 1

State why the electrode potential for the standard hydrogen electrode is equal to 0.00V.

Answer 1

• by definition (it’s the standard)

Question 2

Give one reason, other than cost, why the platinum electrodes are made by coating a porous ceramic material with platinum rather than by using platinum rods

Answer 2

• surface area is increased
• rate of reaction is increased

Question 3

Suggest why the e.m.f. of a hydrogen–oxygen fuel cell, operating in acidic conditions, is exactly the same as that of an alkaline fuel cell

Answer 3

the overall reactions are the same

Question 4

Other than its lack of pollution, state briefly the main advantage of a fuel cell over a re-chargeable cell such as the nickel–cadmium cell when used to provide power for an electric motor that propels a vehicle.

Answer 4

hydrogen and oxygen are supplied continuously

Question 5

Hydrogen–oxygen fuel cells are sometimes regarded as a source of energy that is carbon neutral. Give one reason why this may not be true.

Answer 5

the source of hydrogen may not be carbon neutral

Question 6

tip: when it says “when the cell is used”, what equation is it referencing?

Answer 6

the DISCHARGE equation

Question 7

tip: where are oxidising agents found?

Answer 7

on the LEFT

reducing agents = on the right

Question 8

Suggest one reason why water is not used as a solvent in this cell (lithium cobalt cell)

Answer 8

lithium would react with the water to form lithium hydroxide

Question 9

½O2(g) + 2H+ (aq) + 2e– → H2O(l) +1.23
Au+(aq) + e– → Au(s) +1.68

Answer 9

electrode potential for water is more negative than electrode potential of gold
oxygen is unable to oxidise gold