Electrolysis

Electrolysis

Decomposition of an ionic compound when molten or in an aqueous solution through the passage of an electric current

Anode

Positive Electrode

Cathode

Negetive Electrode

Electrolyte

Molten or aquaeous substance that goes electroysis

Which substance can be formed at the cathode

Metal and Hydrogen

What is formed at the anode

Non metals except hydrogen

Why might metals might be electroplated

Improve their appearance and resist corrosion

How do electrons move through the external circuit to transfer charge

Electrons flow from the negative terminal of the power supply to the cathode giving the cathode its negative charge

How does charge transfer during electrolysis from loss or gain of electrons at the electrodes

At the cathode, cations gain electrons to form atoms

Anions move to the anode and lose electrons

These electrons then flow back to the external circuit back to the power supply completing the circuit

Where do cations move to?

The cathode

Where do anions move

Anode

Identify products made in the electrolysis of molten lead (II) bromide

Brown Bromine Gas is given off

Grey lead deposits on the surface of the electrode

Identify the products made in the electrolysis concentrated aqueous sodium chloride

Hydrogen gas made at the negative electrode

Chlorine gas made at the positive electrode

Na + ions and OH- ions react to form NaOH solution which is left behind

Identify substances produced in electrolysis of dilute sulfuric acid

Hydrogen gas produced at cathode

Oxygen gas and water produced at anode

Sulfuric acid stays in electrolyte

What will form at the anode if concentrated group 7 elements are present

halogen will be formed

What will form at the anode if there are no halogens or dilute halogens

Oxygen

What will form at the cathode if it the metal is more reactive than hydrogen

Hydrogen gas

What will happen in the metal is less reactive than hydrogen

Metal will produce and plate onto the cathode

Describe the electrolysis of aqueous copper sulfate using inert carbon electrodes

Copper forms at the Cathode and will coat the cathode in a pink-brown colour

Oxygen will form at the anode

Blue colour of copper sulfate solution fades over time

OH- ions are oxidized to form oxygen in the equation

4OH- → O2 + 2H2O + 4e-

Describe the electrolysis of aqueous copper sulfate with a copper electrode

Copper is formed at the Cathode increasing its mass

Blue colour of copper sulfate remains the same

Anode decreases in mass as it dissolves as copper atoms are oxidised there by the battery taking away electrons

Copper plated on Cathode is the same lost at the anode

Copper sulfate concentration reamins the same

How does electroplating happen

Surface of one metal coats another metal

The cathode gets electroplated

The anode is made from the pure metal which will coat the other substance

The electrolyte is an aqueous solution of a soluble salt of the pure metal at the anode