ES 3 Manufacturing chlorine

What is brine?

sodium chloride

How is sodium chloride extracted from rock salt?

1. underground mining

2. pumping water into salt and collecting solution

What are the co-products of the electrolysis of sodium chloride?

1. sodium hydroxide

2. Hydrogen

What is the equation at the positive electrode of the electrolysis of sodium chloride?

2Cl^- (aq) —→ Cl₂ (g) + 2e^-

What is the equation at the negative electrode of the electrolysis of sodium chloride?

2H₂O (l) + 2e^- —→ 2OH^- (aq) + H₂ (aq)

What is the overall equation for the electrolysis of sodium chloride solution?

2Cl^- (aq) + 2H₂O (l) —→ Cl₂ (aq) + 2OH^- (aq) + H₂ (g)

Where is iodine naturally found?

seaweed

Cations migrate to the

cathode

Anions migrate to the

anode

What are the usual products at the cathode and anode for a molten salt?

cathode- metal

anode- non-metal, apart from hydrogen

What metals are plated at the cathode?

Metals less reactive than hydrogen

What is released at the cathode when there are no metals less reactive than Hydrogen?

Hydrogen gas

What is the equation at the cathode when Hydrogen gas is released?

2H₂O(l) + 2e^- → 2OH^- (aq) + H₂ (g)

Why are halide ions usually produced at the anode?

they have a greater tendency to be oxidised

What is produced at the anode when there are no halide ions?

oxygen

What is the reaction at the anode when oxygen is produced?

2H₂O (l) —→ O₂ (g) + 4H⁺ (aq) + 4e^-

When may the anode react with the solution?

when the anode is made of the same metal as the metal compound, metal is oxidised at the anode and reduced at the cathode

What is the equation at the cathode for hydrogen made on electrolysis of salts?

2H⁺ (aq) + 2e^- → H₂ (g)

What is the equation at the anode for oxygen made on the electrolysis of hydroxides?

4OH^- (aq) → O₂ (g) + 2H₂O (l) + 4e^-

What are all the products formed at the cathode?

1. Hydrogen gas if the metal is more reactive

2. Metal if it is less reactive than hydrogen

3. Hydrogen if electrolysing acid

What are all the products formed at the anode?

1. Halogen if halide is present

2. Oxygen if no halides

3. Oxygen if electrolysing hydroxides