Electrolysis of Molten Compounds

Electrolysis of molten compounds involves the use of an electric current to break down a compound that is in a molten (liquid) state. 

During this process, the compound is melted, allowing its ions to move freely and conduct electricity.

The compound is typically heated until it reaches a molten state, enabling the ions to become mobile and carry electric charge. 

The compound is placed in a container or crucible that can withstand high temperatures. 

Two electrodes, the anode, and the cathode, are immersed in the molten compound. The anode is connected to the positive terminal of the power source, and the cathode is connected to the negative terminal. When the electric current is passed through the molten compound, chemical reactions occur at the electrodes.

At the Anode (positive electrode):

• Anions (negatively charged ions) from the compound are attracted to the anode.
• These anions lose electrons and undergo oxidation, forming new elements or compounds.

At the cathode (negative electrode):

• Cations (positively charged ions) from the compound are attracted to the cathode.
• These cations gain electrons and undergo reduction, forming new elements or compounds.

Electrolysis of Molten Sodium Chloride

In the electrolysis of molten sodium chloride (NaCl), 

• Sodium metal (Na) is produced at the cathode 
• Chlorine gas (Cl2) is produced at the anode.

This type of electrolysis is often used in the extraction of metals from their ores, such as the production of aluminum from aluminum oxide (Al2O3) or the extraction of sodium from sodium chloride (NaCl).

• The molten state allows for the free movement of ions, facilitating the transfer of charge and the desired chemical reactions.

Electrolysis of Molten Lead(II) Bromide

In the electrolysis of Molten Lead(II) Bromide(PbBr2), 

• Lead metal (Pb) is produced at the cathode 
• Bromine gas (Br2) is produced at the anode.

Lead(II) bromide (PbBr2) is a compound that can be electrolyzed when it is in a molten state. 

• Heat lead(II) bromide (PbBr2) until it melts and becomes a liquid.
• Place two electrodes (anode and cathode) into the molten lead(II) bromide.

At the Anode (Positive Electrode):

The anode attracts negatively charged ions (anions) from the molten lead(II) bromide.

• At the anode, bromide ions (Br-) are oxidized.
• Each bromide ion loses two electrons and forms bromine gas (Br2):

                      2 Br- (molten) → Br2 (g) + 2e-

Cathode (Negative Electrode):

The cathode attracts positively charged ions (cations) from the molten lead(II) bromide.

• At the cathode, lead(II) ions (Pb2+) are reduced.
• Each lead(II) ion gains two electrons and forms lead metal (Pb):

Pb2+ (aq)(molten) + 2 e– → Pb (l)

The overall reaction of the electrolysis of molten lead(II) bromide can be represented as follows:

2 PbBr2 (molten)  →  2 Pb (l) + Br2 (g)

Observations:

• At the anode, brownish-red bromine gas (Br2) is produced.
• At the cathode, metallic lead (Pb) is formed as a liquid.

Molten Lead Bromide Animation Insert

This electrolysis process allows the extraction of lead metal from lead(II) bromide.The molten state of lead(II) bromide enables the ions to move freely and facilitate the flow of electric charge.

Through this electrolysis, the compound is broken down into its constituent elements, lead and bromine.