Electrolysis of Aqueous Solutions

Question 1

What ions are present in aqueous solutions besides the ions from the ionic compound?

Answer 1

Hydrogen ions (H’) and hydroxide ions (OH-)

These ions are derived from the dissociation of water.

Question 2

What is produced at the cathode if hydrogen ions and metal ions are present, and the metal is more reactive than hydrogen?

Answer 2

Hydrogen gas

Example: Sodium ions produce hydrogen gas.

Question 3

What happens at the cathode if the metal ions are less reactive than hydrogen?

Answer 3

A solid layer of the pure metal is produced

Example: Copper ions produce copper metal.

Question 4

What is produced at the anode if hydroxide and halide ions are present?

Answer 4

Molecules of chlorine, bromine, or iodine

The specific halogen produced depends on the halide present.

Question 5

What is formed at the anode if no halide ions are present?

Answer 5

Oxygen

The hydroxide ions are discharged to produce oxygen.

Question 6

In a solution of copper(II) sulfate (CuSO4), which ions are present?

Answer 6

• Cu2+
• SO4^2-
• H’
• OH-

These ions contribute to the electrolysis process.

Question 7

What is produced at the cathode when electrolysis occurs in a copper(II) sulfate solution?

Answer 7

Copper metal

Copper is less reactive than hydrogen.

Question 8

What is produced at the anode during the electrolysis of copper(II) sulfate?

Answer 8

Oxygen and water

Oxygen can be observed as bubbles.

Question 9

In a sodium chloride (NaCl) solution, what happens at the cathode?

Answer 9

Hydrogen gas is produced

Sodium metal is more reactive than hydrogen.

Question 10

What is produced at the anode in a sodium chloride solution?

Answer 10

Chlorine gas

Chloride ions are present in the solution.

Question 11

What is the half equation for the negative electrode during the electrolysis of sodium chloride?

Answer 11

2H+ + 2e- -> H2

This represents the reduction of hydrogen ions.

Question 12

What is the half equation for the positive electrode during the electrolysis of sodium chloride?

Answer 12

2Cl- -> Cl2 + 2e-

This represents the oxidation of chloride ions.

Question 13

What is the ionic equation for the electrolysis of aqueous sodium chloride?

Answer 13

2H+ + 2Cl- -> H2 + Cl2

This combines the half equations.

Question 14

What occurs when a halide isn’t present in the aqueous solution during electrolysis?

Answer 14

The half equation for the anode is: 4OH- -> O2 + 2H2O + 4e-

This indicates oxygen production instead of a halogen.