SPM Chemistry

Electrolysis of Molten Ionic Compound

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Electrolysis of Molten Ionic Compound

Example – Electrolysis of MOLTEN Lead (II) Bromide

Figure above shows the apparatus set up for electrolysis of molten lead (II) bromide.
The electrolysis process start when lean (II) bromide start melting.

At the CathodeAt the Anode

Ion presence:

Pb2+

Ion presence:

Br–
Observation
When electricity is flowing, a silvery deposit of lead metal forms on the cathode. In fact, as it is molten, it is more likely to drip off in a molten blob.		Observation
When electricity is flowing, brown fumes of bromine gas are seen at the anode.

Half equation

Pb2+ + 2e —> Pb

Half equation

2Br– —> Br2 + e

Summary:
 the lead(II) bromide is split into its component elements :

PbBr2 —> Pb + Br2
Explanation

At the Anode

  1. The negatively charged bromide ions move to the positive anode
  2. each bromine ion loses an electron to form a bromine atom.
  3. two of these newly formed atoms combine to form a bromine molecule (bromine gas).

At the Cathode

  1. The positively charged lead(II) ions, move to the negative cathode,
  2. each ion gains two electrons to form a lead atom.