Electrolysis: Key Concepts and Applications IGCSE

What is produced at the anode during the electrolysis of molten sodium chloride?

• Sodium

• Chlorine

• Hydrogen

• Oxygen

Answer explanation

During the electrolysis of molten sodium chloride, sodium ions migrate to the cathode and gain electrons to form sodium metal, while chloride ions lose electrons at the anode, producing chlorine gas.

During the electrolysis of copper(II) sulfate solution using copper electrodes, what happens to the mass of the anode?

• It increases

• It decreases

• It remains the same

• It doubles

Answer explanation

During electrolysis, copper ions from the anode dissolve into the solution, causing the mass of the anode to decrease. Therefore, the correct answer is that the mass of the anode decreases.

What is the main product at the cathode during the electrolysis of water?

• Oxygen

• Hydrogen

• Chlorine

• Sodium

Answer explanation

During the electrolysis of water, water molecules are split into hydrogen and oxygen. At the cathode, reduction occurs, producing hydrogen gas as the main product, while oxygen is produced at the anode.

What is the role of the anode in electrolysis?

• To supply electrons to the solution

• To collect electrons from the solution

• To provide a surface for the reaction

• To act as a catalyst

Answer explanation

In electrolysis, the anode collects electrons from the solution, facilitating oxidation reactions. This is crucial for the overall process, as it allows the flow of current and drives the chemical reactions at the electrodes.

Which of the following is an application of electrolysis?

• Distillation

• Electroplating

• Filtration

• Evaporation

Answer explanation

Electrolysis is used in electroplating, which involves depositing a layer of metal onto a surface using electric current. This process enhances appearance and prevents corrosion, making electroplating a key application of electrolysis.

What is produced at the anode during the electrolysis of copper(II) sulfate solution using inert electrodes?

• Copper

• Sulfur dioxide

• Oxygen

• Hydrogen

Answer explanation

During the electrolysis of copper(II) sulfate solution with inert electrodes, water is oxidized at the anode, producing oxygen gas. Therefore, the correct answer is oxygen.

During the electrolysis of copper(II) sulfate solution, how will the pH of the electrolyte change?

• It will become neutral

• It will increase

• It will decrease

• There will be no observable change

Answer explanation

During the electrolysis of copper(II) sulfate solution with inert electrodes, water is oxidized at the anode, producing oxygen gas and copper ions are reduced forming copper. This will leave H⁺ ions and SO₄^2- ions in solution. This is sulfuric acid, so the pH is lowered (low pH i.e. below 7 is acidic).

During the electrolysis of sodium chloride solution, which gas is produced at the cathode?

• Chlorine

• Oxygen

• Hydrogen

• Nitrogen

Answer explanation

During the electrolysis of sodium chloride solution, water is reduced at the cathode, producing hydrogen gas. Therefore, hydrogen is the gas produced at the cathode.

During the electrolysis of a sodium chloride solution, how will the pH of the electrolyte change as the current flows?

• It will become neutral

• It will increase

• It will decrease

• There will no observable change

Answer explanation

As the hydrogen and chlorine gas leave the electrolyte at the electrodes, sodium ions and hydroxide ions will remain making the solution alkaline (higher pH).

Which of the following is a common use of electrolysis in industry?

• Water purification

• Metal extraction

• Food preservation

• Textile dyeing

Answer explanation

Electrolysis is commonly used in metal extraction, such as aluminum and copper, where it helps separate metals from their ores. This process is essential for obtaining pure metals for industrial applications.