Chemistry Electrolysis

What is electrolysis?

The decomposition of an ionic compound using electricity

What are the two electrodes used in electrolysis?

Cathode- negative electrode

Annode- positive electrode

Which electrode do positive and negative ions move towards?

Positive ions → cathode (–)

Negative ions → annode (+)

Opposites attract

What happens to the ions at the electrodes during electrolysis?

At the cathode positive ions gain electrons- are reduced

At the annode negative ions lose electrons- are oxidised

Why must an ionic compound be molten or dissolved for electrolysis?

Because the ions needs to be free to move and carry the electric charge.

Why can electrolysis of an aqueous solution produce different products from molten electrolysis?

Because the solution contains ions from the compound and ions from the water so there is competition between ions and electrodes

What is produced at the cathode during electrolysis of an aqueous solution?

A metal or hydrogen is produced.

If the metal is less reactive then hydrogen the metal forms.

If the metal is more reactive than hydrogen, hydrogen forms.

What is produced at the annode during electrolysis of an aqueous solution?

Halide ions→ halogen is produced e.g. chloride ions form chlorine

Otherwise oxygen forms.

What does a half equation show?

It shows the electron transfer taking place at one electrode during electrolysis.

What happens to electrons in the reduction half equation?

Electrons are gained

What happens to electrons in the oxidisation half equation?

Electrons are lost.