Electrolysis flashcards

Define electrolysis

Electrolysis is the process of using an electric current to decompose or break down a molten or aqueous ionic compound.

Why do the electrodes have to be inert?

To ensure that they don’t interfere / react with the process.

What is an electrolyte?

An ionic compound in a molten or dissolved solution that conducts electricity.

What is the anode?

The positive electrode.

What is the cathode?

The negative electrode.

Which way do electrons flow in the circuit during electrolysis?

Electrons flow from the anode to the cathode.

What are cations?

Positive ions that are attracted to the negative cathode.

What are anions?

Negative ions that are attracted to the positive anode.

Why are cations attracted to the cathode?

Positive cations are attracted to the negative cathode as opposite charges attract.

Why are anions attracted to the anode?

Negative anions are attracted to the positively charged anode as opposite charges attract.

Why do covalent compounds not conduct electricity?

They have no free ions to carry charge.

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

Molten lead.

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

Brown bromine gas.

What would be the products of electrolysis of molten zinc chloride?

Zinc at the cathode and chlorine at the anode.

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

Graphite or platinum.

How does chlorine form during the electrolysis of lead (II) chloride?

Two chloride ions are attracted to the anode where they each lose one electron and bond to form a molecule of chlorine.

Is a non-metal or metal formed at the anode?

Non-metal

Is a non-metal or metal formed at the cathode?

Metal

What determines the method of extraction for a metal?

Its position in the reactivity series.

Why is electrolysis used to extract metals above carbon in the reactivity series?

Because they are too reactive to be reduced by carbon.

Why is electrolysis expensive?

Because large amounts of energy are used to melt the ores and produce the electrical current.

What is the main ore of aluminium?

Bauxite

Why is cryolite used in the extraction of aluminium?

It lowers the melting point without interfering with the reaction reducing energy costs.

What is produced at the cathode during the extraction of aluminium?

Aluminium.

What is produced at the anode during the extraction of aluminium?

Oxygen.

Why does the anode need to be replaced regularly in aluminium extraction??

Because the carbon in the graphite anode reacts with oxygen to produce CO2 causing it to wear away.

How are metals below carbon in the reactivity series extracted?

By heating with carbon

Write the half equation for the reduction of aluminium ions at the cathode

Al³+ 3e^- = Al

Write the half equation for the oxidation of oxide ions at the anode.

2O²- = O2 + 4e^-

Why are ions always present in aqueous solutions?

They always have H+ and OH- ions present from the splitting of water molecules.

If halide ions are present in the aqueous electrolyte, what happens?

They are discharged at the anode.

What gas is produced at the anode if no halide ions are present in the electrolyte?

Oxygen

What ions are attracted to the cathode?

H+ ions and metal ions.

How is the product at the cathode determined?

By the position in the reactivity series relative to hydrogen

What is the test for hydrogen gas?

A squeaky pop

What is the test for oxygen gas?

Relighting a glowing splint

What is the test for chlorine gas?

Turning damp blue litmus paper red and then bleaching it white.