Electrolysis (C4.1)

What is the electrolyte in electrolysis?

• A non-ionic compound

• An ionic compound in molten or dissolved solution

• A gas

• A solid ionic compound

Answer explanation

The electrolyte in electrolysis must be an ionic compound that can conduct electricity when molten or dissolved in a solution, allowing ions to move freely and facilitate the electrochemical reactions.

What is produced at the cathode during the electrolysis of molten lead(II) bromide?

• Bromine gas

• Hydrogen gas

• Lead metal

• Chlorine gas

Answer explanation

During the electrolysis of molten lead(II) bromide, lead ions are reduced at the cathode, producing lead metal. Bromine gas is produced at the anode, not at the cathode.

What type of electrodes are typically used in the electrolysis of molten compounds?

• Copper electrodes

• Aluminum electrodes

• Graphite or platinum electrodes

• Iron electrodes

Answer explanation

In the electrolysis of molten compounds, graphite or platinum electrodes are preferred due to their high conductivity and resistance to corrosion. Other materials like copper or aluminum may react with the molten substance.

What gas is produced at the anode during the electrolysis of brine?

• Nitrogen gas

• Oxygen gas

• Chlorine gas

• Hydrogen gas

Answer explanation

During the electrolysis of brine (saltwater), chlorine gas is produced at the anode. This occurs as chloride ions are oxidized, releasing chlorine gas, while hydrogen gas is produced at the cathode.

What is the test for hydrogen gas?

• A lit splint produces a squeaky pop

• It produces a color change in water

• Damp litmus paper turns blue

• A glowing splint relights

Answer explanation

The test for hydrogen gas is that a lit splint produces a squeaky pop sound. This occurs due to the rapid combustion of hydrogen when it reacts with oxygen, confirming its presence.

What is brine?

• A solid ionic compound

• A concentrated solution of aqueous sodium chloride

• A type of gas

• A non-ionic solution

Answer explanation

Brine is specifically defined as a concentrated solution of sodium chloride (salt) in water. It is not a solid ionic compound, gas, or non-ionic solution, making the correct choice 'A concentrated solution of aqueous sodium chloride'.

What is produced at the anode during the electrolysis of dilute sulfuric acid?

• Hydrogen gas

• Lead metal

• Oxygen gas

• Chlorine gas

Answer explanation

During the electrolysis of dilute sulfuric acid, water is oxidized at the anode, producing oxygen gas. Therefore, the correct answer is oxygen gas.

What determines which ions are discharged at the electrodes during electrolysis of aqueous solutions?

• The volume of the solution

• The concentration of the solution

• The relative reactivity of the elements involved

• The temperature of the solution

Answer explanation

The ions discharged during electrolysis depend on their relative reactivity. More reactive ions are less likely to be discharged compared to less reactive ones, which is why this factor is crucial in determining the outcome.

What is oxidation in terms of electron transfer?

• Transfer of neutrons

• Transfer of protons

• Loss of electrons

• Gain of electrons

Answer explanation

Oxidation refers to the loss of electrons from an atom or molecule. This process increases the oxidation state of the substance, making 'loss of electrons' the correct choice in the context of electron transfer.

What is produced at the cathode during electrolysis of aqueous copper sulfate?

• Copper metal

• Oxygen gas

• Hydrogen gas

• Chlorine gas

Answer explanation

During the electrolysis of aqueous copper sulfate, copper ions are reduced at the cathode, resulting in the deposition of copper metal. Therefore, the correct answer is copper metal.