6.2 Electrolysis of Molten Compounds

Electrolysis process
■ Electrolysis

►

A decomposition process of an electrolyte by an electric current into its components.

■ Electrolytic cell

	►	A type of cell which uses electrical energy to produce chemical reaction.
	►	The animation below shows the basic structure of an electrolytic cell

■ This video contains information about electrolysis of molten compounds.

Laboratory Activity 6.2.1: Electrolysis of molten compounds

Predicting products of electrolysis of molten compounds
■ Electrolysis of molten A_xB_y electrolyte

	►	Metal compound is formed at the cathode.
	►	Non-metal is formed at the anode.
	►	In general, the electrolysis of molten electrolyte can be summarized as shown in the following table: Salt in molten state At anode (+) At cathode (-) Movements of ion to electrode Bx- Ay+ Half equation Bx- → B + xe- Ay++ ye- → A
	►	Half-equation shows what happens at one of the electrodes during electrolysis.

✍ Worked-example 6.2(a)
Predict the products of electrolysis of molten sodium chloride at anode and cathode.
Solution 

Salt in molten state	At anode (+)	At cathode (-)
Movements of ion to electrode	Cl-	Na+
Half equation	2Cl- → Cl2 + 2e-	Na++ e- → Na
Observation	Greenish-yellow gas	Grey metal is formed
Product	Chlorine gas	Sodium metal

✍ Worked-example 6.2(b)
Predict the products of electrolysis of molten magnesium oxide at anode and cathode.
Solution 

Salt in molten state	At anode (+)	At cathode (-)
Movements of ion to electrode	O2-	Mg2+
Half equation	2O2- → O2 + 4e-	Mg2++ 2e- → Mg
Observation	Colourless gas are released	Grey metal is formed
Product	Oxygen gas	Magnesium metal

← 6.1 Properties of Electrolytes and Non-electrolytes

6.3 Electrolysis of Aqueous Solutions →

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