Electrochemistry Part 2

Question 1

Name the application of redox reactions.

Answer 1

Batteries

Question 2

Define REDOX reaction

Answer 2

Reactions involving the transfer of electrons

Question 3

Define oxidation and reduction

Answer 3

Oxidation - Atom loses electrons, thus oxidation number increases
Reduction - Atom gains electrons, thus oxidation number decreases

Question 4

Define oxidising and reducing agents

Answer 4

Oxidising agent - Substance that gets reduced (other atom gets oxidised), e.g. Oxygen, causes Hydrogen to get oxidised
Reducing agent - Substance that gets oxidised (other atom gets reduced), e.g. Hydrogen, causes Oxygen to get reduced

Question 5

What are the 3 applications of electrolysis?

Answer 5

Electroplating
Purification of copper/ refining copper
Electrolysis of concentrated sodium chloride

Question 6

Define electrolysis

Answer 6

Decomposition of an ionic compound, either molten or aqueous, by using an electric current. Carried out in an electrolytic cell.

Question 7

What does an electrolytic cell consist of?

Answer 7

Battery
Positive electrode (Anode)
Negative electrode (Cathode)
Electrolyte (aqueous or molten substance that contains electricity)

Question 8

Define electrode

Answer 8

Electrical conductors that allow the flow of charge
Must be inert (no reaction)
E.g. Platinum or graphite

Question 9

Define electrolyte

Answer 9

Substance being broken down
Liquid or aqueous - conducts electric current
Must be aqueous or molten - ions can move to their oppositely charged electrodes
Can be used up, become more dilute or become more concetrated

Question 10

What are the 3 steps for electrolysis in molten compounds?

Answer 10

1. Write down all the ions present
2. Write down ions that with move to the anode (+ electrode)
3. Write down ions that with move to the cathode (- electrode)

Question 11

What are other names for aqueous compounds?

Answer 11

Solution
Dilute solution
Concentrated solution

Question 12

What are the 4 ions present in an aqueous compound?

Answer 12

Positive metal ion
Negative non-metal ion
H+
OH-

Question 13

What is the rule for aqueous compounds?

Answer 13

The ion lowest down on the reactivity series gets discharged

Question 14

What are the 3 steps for electrolysis of aqueous compounds?

Answer 14

1. Write down all the ions present
2. Write down ions that with move to the anode (+ electrode)
3. Write down ions that with move to the cathode (- electrode)

The leftovers join to form the electrolyte

Question 15

What happens when OH- is discharged (i.e. lower down than other negative ions)?

Answer 15

The reaction at the anode is:

4OH- —> 2H20 + O2 + 4e