CHEMICAL CHANGE: ELECTROCHEMICAL REACTIONS

Question 1

Galvanic cell

Answer 1

A cell in which chemical energy is converted into electrical energy. A galvanic (voltaic) cell has self-sustaining electrode reactions.

Question 2

Electrolytic cell

Answer 2

A cell in which electrical energy is converted into chemical energy.

Question 3

Redox reaction

Answer 3

A reaction in which an electron transfer takes place.

Question 4

Oxidation

Answer 4

A loss of electrons./An increase in oxidation number.

Question 5

Reduction

Answer 5

A gain of electrons./A decrease in oxidation number.

Question 6

Oxidising agent

Answer 6

A substance that is reduced/gains electrons/whose oxidation number decreases.

Question 7

Reducing agent

Answer 7

A substance that is oxidised/loses electrons/whose oxidation number increases.

Question 8

Anode

Answer 8

The electrode where oxidation takes place.

Question 9

Cathode

Answer 9

The electrode where reduction takes place.

Question 10

Electrolyte

Answer 10

A solution that conducts electricity through the movement of ions.

Question 11

Electrolysis

Answer 11

The chemical process in which electrical energy is converted to chemical energy OR the use of electrical energy to produce a chemical change.

Question 12

Salt bridge

Answer 12

The connection between two half-cells needed to ensure electrical neutrality in the cell. OR A component used in a galvanic cell to complete the circuit.

Question 13

Electrodes

Answer 13

An electrical conductor used in a galvanic cell to make contact with a nonmetallic part of the circuit e.g. the electrolyte.

Question 14

Cell notation

Answer 14

A short way to represent a galvanic cell. When writing cell notation, the following convention should be used:

*The H2|H+ half-cell is treated just like any other half-cell.

*Cell terminals (electrodes) are written on the outside of the cell notation.

*Active electrodes: reducing agent | oxidised species || oxidising agent | reduced species

*Inert electrodes (usually Pt or C):
Pt | reducing agent | oxidised species || oxidising agent | reduced species | Pt Example: Pt | Cℓ-(aq) |Cℓ2(g) || F2(g) | F-(aq) | Pt

Question 15

Overall cell reaction

Answer 15

The reaction obtained by combining two half-reactions.

Question 16

Positive value of the standard emf

Answer 16

The reaction is spontaneous under standard conditions.

Question 17

Standard conditions for a galvanic cell

Answer 17

Temperature: 25 °C / 298 K Concentration:
1 mol∙dm-3 Pressure (gases only):
101,3 kPa / 1 atmosphere

Question 18

Standard hydrogen electrode

Answer 18

The reference electrode used to compile the Table of Standard Reduction Potentials.
The hydrogen half-cell was given a standard reduction potential of 0 V.
Half-cell notation:
Pt | H2(g) | H+(aq) Half-reaction: 2H+ + 2e- ⇌ H2

Question 19

Electroplating

Answer 19

The covering of an object with a metal by making it the cathode in an electrolytic cell.

Question 20

Bauxite

Answer 20

The ore from which aluminium is recovered.

Question 21

Cryolite

Answer 21

An aluminium compound in which aluminium oxide is dissolved to reduce the cost of the extraction of aluminium. Cryolite has a lower melting point than aluminium oxide.