Electrochemical Reactions

Question 1

Oxidation

Answer 1

A loss of electrons, an increase in ON

Question 2

Reduction

Answer 2

A gain of electrons, a decrease in ON

Question 3

Galvanic cell (voltaic cell)

Answer 3

An electrochemical cell in which chemical energy is converted into electrical energy.
This is as a result of a self-sustaining spontaneous reaction.

Question 4

Electrolytic cell

Answer 4

An electrochemical cell in which electrical energy is converted into chemical energy.
This occurs by means of a non-spontaneous redox reaction using a supply of electrical energy.

Question 5

Oxidising agent

Answer 5

A substance that is reduced/gains electrons in a redox reaction

Question 6

Reducing agent

Answer 6

A substance that is oxidised/loses electrons in a redox reaction

Question 7

Electrode

Answer 7

A solid electric conductor through which an electric current enters of leaves an electrolytic cell or other medium

Question 8

Anode

Answer 8

The electrode where oxidation takes places

ANOX

Question 9

Cathode

Answer 9

The electrode where reduction takes place

REDCAT

Question 10

Electrolyte

Answer 10

A solution/liquid dissolved substance that conducts electricity through the movement of ions

A solution which is able to conduct electrical charge due to the movement of free ions through the solution

Question 11

Electrolysis

Answer 11

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

Question 12

Spectator ion

Answer 12

An ion which does not chemically participate in the reaction, so can be ignored when considering the electrochemistry taking place in a cell

Question 13

Standard electrode potential

Answer 13

The voltage measure for a half cell under standard conditions when the half cell is connected to a standard hydrogen electrode to form a galvanic cell

Question 14

What is the direction of current flow in a galvanic cell

Answer 14

Always from anode (-) to cathode (+)

Negative electrode to positive electrode

Question 15

What is the direction of current flow in an electrolytic cell
and WHY

Answer 15

From positive to negative.
The anode is now the positive electrode, the cathode is now the negative electrode

WHY?
due to the fact that this is how the electrodes are connected to the external power supply that supplies the electrical energy to t sustain the electrochemical reaction.

Question 16

Salt bridge

Answer 16

a tube containing an electrolyte/ filled with a saturated soution of salts (4) providing electrical contact between two solutions.

Question 17

What is inside a salt bridge and why those specific electrolyte solutions

Answer 17

A saturated solution of:

• potassium chloride (KCl)
• sodium chloride (NaCl)
• potassium nitrate (KNO3)
• sodium sulphate (Na2SO4)

These electrolytes used because they are generally unreactive towards the chemical substances in the individual beakers.

Question 18

2 functions of a salt bridge (in a galvanic cell)

Answer 18

1. To connect the two half cells together to complete the circuit
2. To maintain ionic neutrality in each of the half cells

Question 19

Do galvanic cells use direct redox reactions and why?

Answer 19

No, Galvanic cells use indirect redox reaction because chemical contents in each cell do not mix directly.

Question 20

Half-cell

Answer 20

A half-cell is a structure that contains a conductive electrode and a surrounding conductive electrolyte

Question 21

Corrosion (in galvanic cell process)

Answer 21

Process whereby ions are introduced onto the electrolyte form the metal electrode and thus causing that metal electrode to decrease in mass

Question 22

Plating (in galvanic cell process)

Answer 22

When metal ions form and coat he metal electrode. These ions are removed from the electrolyte solution and are transported to the metal electrode thus increasing its mass.

Question 23

on table 4B which direction is oxidation and which reduction (horizontally)

Answer 23

Reduction –> left to right

Oxidation –> right to left

Question 24

In an electrolytic cell electrodes are generally made of… why?

Answer 24

Carbon (graphite)
WHY?
Metals like platinum can be used as electrodes but they are quite expensive. A cheaper alternative that is resistant to corrosion is graphite. As graphite conducts electricity and is resistant to corrosion it is used to make electrodes for electrolysis.

Question 25

Energy conversion in galvanic cell

Answer 25

Chemical energy to electrical energy

Question 26

Energy conversion in electrolytic cell

Answer 26

Electrical energy to chemical energy

Question 27

Direct flow of electric flow of current

Answer 27

Electrons flow through the external circuit from anode to cathode / from negative to positive

Electron current

Question 28

Conventional current

Answer 28

From positive to negative in though a circuit, in the opposite of the flow of electrons

Question 29

What is cell notation

Answer 29

Cell notation is the simplest and most convenient way and is an abbreviated representation of the reactions taking place in a galvanic cell.

Question 30

What are the standard conditions for the measurement of standard electrode potentials

Answer 30

• Temperature 298 K or 25 °C
• Concentration of solutions must be 1 mol.dm-3
• Pressure of 101,3 kPa (atmospheric pressure) is a gaseous half cell is used