Electrochemistry

Question 1

redox reaction

Question 2

oxidation

Question 3

reduction

Question 4

oxidising agent

Question 5

reducing agent

Question 6

anode

Question 7

cathode

Question 8

electrolyte

Question 9

Use the table of standard electrode potentials (SEP table) to:
- Predict the chemical species which is oxidised in a redox
reaction and write an equation for the oxidation half-reaction
- Predict the chemical species which is reduced in a redox
reaction and write an equation for the reduction half-reaction
- Write the overall balanced ionic reaction equation by combining
the two half-reactions
- Identify the oxidising agent and the reducing agent for a redox
reaction
- Determine the spontaneity of a redox reaction under standard
conditions

Question 10

Identify the spectator ion in a redox process and know that the
spectator ion does not take part in the electron transfer

Question 11

Describe the galvanic cell in terms of:
- self-sustaining electrode reactions
- conversion of chemical energy to electrical energy

Question 12

Describe:
- the movement of ions through the solutions
- the electron flow in the external circuit of the cell
- the observations in the half-cells

Question 13

State the functions of the salt bridge as
- completing the circuit
- maintaining electrical neutrality in the half-cells

Question 14

Describe how the salt bridge maintains electrical neutrality
in the half-cells by referring to the movement of ions in and
out of the salt bridge

Question 15

State the standard conditions under which standard
electrode potentials are determined

Question 16

Describe the standard hydrogen electrode and explain its
role as the reference electrode

Know that when used as a reference electrode the standard
hydrogen electrode is connected as the anode (to the
negative terminal of a voltmeter) even though it may not
spontaneously act as the anode

Question 17

Explain how standard electrode potentials can be
determined using the reference electrode and state the
convention regarding positive and negative values

Question 18

Galvanic cell theory

Answer 18

State that the galvanic cell has the capacity to deliver
current until the reaction reaches chemical equilibrium or
has run to completion

State that once a galvanic cell reaches chemical equilibrium
or has run to completion the voltage of the cell equals zero

Question 19

Qualitatively, using Le Châtelier’s principle, predict the
effect of changing concentration on the voltage of a
galvanic cell.

Question 20

State that increased surface area of the terminals increases
the rate of the reaction which therefore increases the
maximum current that the cell can deliver but does not
affect the emf of the cell

Question 21

State that the wider, shorter and/or more conductive salt
bridge lowers internal resistance thereby increasing the
maximum current that the cell can deliver but does not
affect the emf of the cell

Question 22

Describe the electrolytic cell in terms of:
- electrode reactions that are sustained by a supply of electrical
energy
- conversion of electrical energy into chemical energy

Question 23

Identify or suggest suitable inert electrodes for use in
electrolysis and give reasons for their suitability

Question 24

Identify the predominant half-reaction taking place at the
anode and cathode during electrolysis of an AQUEOUS
solution

Question 25

Explain the role of concentration when predicting the
predominant anode half-reaction during electrolysis

Question 26

Explain under what circumstances the anode itself will
be oxidised in preference to the ions in the solution

Question 27

Explain that the inherent reactivity (electrode potentials/
strength of agents) will determine which half-reaction
will be predominant at the cathode

Question 28

**When given a diagram of a cell or other relevant
information, predict and explain features of the following
electrolytic processes:
- The electrolysis of a solution of copper(II) chloride
- Simple electroplating of objects in aqueous solutions of
metal ions, demonstrating an understanding of why it is
not possible to electroplate using metals ions which are
weaker oxidising agents than water (H2O) under
standard conditions
- The electrorefining of copper, including the possible
competitive reactions that can take place at the
electrodes due to the presence of impurities
- The electrolysis of a concentrated solution of sodium
chloride (brine) and its use in the chlor-alkali industry
using either the mercury cell, the diaphragm cell or the
membrane cell including:
o the potential risks to the environment posed by
using these cells
o the relative purity of the products obtained in each of
these cells
o the relative cost of running each of these cells
- Know that in the mercury cell, the nature of the mercury
cathode adjusts the electrode potentials of the Na+ ions
and water, so that the reduction of Na+ is now more
likely than that of water
- The recovery of aluminium from bauxite, including:
o the use of cryolite and its effect on the cost of
running this cell
o the corrosion of the graphite anodes
o the potential risks to the environment posed by
using this cell