Topic 4: Electrochemistry

Question 1

What is electrolysis?

Answer 1

The decomposition of an ionic compound, when molten or in aqueous solution, by passing an electric current.

Question 2

What is needed for electrolysis to happen?

Answer 2

Free-moving ions or mobile electrons.

Question 3

What is an electrolyte?

Answer 3

A molten or aqueous substance that undergoes electrolysis.

Question 4

What are electrodes?

Answer 4

Metal or graphite rods that conduct electricity into or out of the electrolyte.

Question 5

What is the anode?

Answer 5

The positive electrode.

Question 6

What is the cathode?

Answer 6

The negative electrode.

Question 7

What is an anion?

Answer 7

A negatively charged ion moving to the anode.

Question 8

What is a cation?

Answer 8

A positively charged ion moving to the cathode.

Question 9

What are inert electrodes?

Answer 9

Electrodes like graphite, carbon, or platinum that do not react during electrolysis.

Question 10

What happens at the cathode?

Answer 10

Reduction — cations gain electrons.

Question 11

What happens at the anode?

Answer 11

Oxidation — anions lose electrons.

Question 12

What does OIL RIG mean?

Answer 12

Oxidation Is Loss, Reduction Is Gain (of electrons).

Question 13

Electrolysis of molten lead(II) bromide: What forms?

Answer 13

Lead at cathode; Bromine at anode.

Question 14

Electrolysis of concentrated aqueous sodium chloride: What forms?

Answer 14

Hydrogen at cathode; Chlorine at anode.

Question 15

Electrolysis of dilute sulfuric acid: What forms?

Answer 15

Hydrogen at cathode; Oxygen at anode.

Question 16

Electrolysis of aqueous copper(II) sulfate with graphite electrodes: What forms?

Answer 16

Copper at cathode; Oxygen at anode.

Question 17

Electrolysis of aqueous copper(II) sulfate with copper electrodes: What happens?

Answer 17

Copper forms at both electrodes; Blue color stays the same.

Question 18

How do electrons move during electrolysis?

Answer 18

Through the external circuit from anode to cathode.

Question 19

How do ions move during electrolysis?

Answer 19

Cations move to the cathode; anions move to the anode.

Question 20

What forms at the cathode in molten electrolysis?

Answer 20

Metals or hydrogen.

Question 21

What forms at the anode in molten electrolysis?

Answer 21

Non-metals (other than hydrogen).

Question 22

Example half-equation at anode (oxidation)?

Answer 22

2Cl⁻ → Cl₂ + 2e⁻

Question 23

Example half-equation at cathode (reduction)?

Answer 23

2H⁺ + 2e⁻ → H₂

Question 24

What is electroplating?

Answer 24

Coating an object with a layer of another metal using electrolysis.

Question 25

In electroplating, what is the anode and cathode?

Answer 25

Anode = pure metal; Cathode = object being plated.

Question 26

What is refining metals by electrolysis?

Answer 26

Using electrolysis to purify metals (e.g., copper).

Question 27

What happens at the anode during copper refining?

Answer 27

Impure copper loses mass (Cu → Cu²⁺ + 2e⁻).

Question 28

What happens at the cathode during copper refining?

Answer 28

Pure copper gains mass (Cu²⁺ + 2e⁻ → Cu).

Question 29

What does a hydrogen–oxygen fuel cell produce?

Answer 29

Electricity and water.

Question 30

What is the main equation in a hydrogen–oxygen fuel cell?

Answer 30

2H₂ + O₂ → 2H₂O

Question 31

Two advantages of hydrogen–oxygen fuel cells?

Answer 31

Renewable source, emission-free (no carbon pollution).

Question 32

Two disadvantages of hydrogen–oxygen fuel cells?

Answer 32

Need for large fuel tanks, expensive and fewer hydrogen filling stations.