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Electrolysis


The Principle of Electrolysis - Worst topic ever


To kick-start an electrolysis set-up, an input of energy is required. Sources of energy usually come in the form of batteries or a power supply. The energy provided for this non-spontaneous reaction will be converted from ELECTRICAL energy to CHEMICAL energy. The set-up of an electrolysis experiment contains a complete electrical circuit where electrons flow in only one direction, which is from anode to cathode. These electrons are transferred from the anode to the voltage source then back to the cathode. During electrolysis, the electric charge flows continually through the liquid and the connecting wires. Ions move through the electrolyte and electrons move through the wire. This is what keeps the current continuous.

An aqueous solution or ionic compound in molten state is used because ionic compounds in the form of a Giant Ionic Crystal Lattice has ions which are fixed in position by strong electrostatic attraction between oppositely charged ions, hence it is immobile. However, in molten state or an aqueous solution, ions of the ionic compound are mobile and free to move. On this basis, electrolysis can by used to separate the ionic compounds into its respective elements.

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Sodium Chloride Lattice Structure (solid) Sodium Chloride Solution(aqueous)


As we can see from the picture in the centre, ions are mobile and they are moving freely in the electrolyte.
However when a current is passed through the electrolyte all cations will be attracted to the CATHODE and all anions to the ANODE


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Molten Sodium Chloride (liquid)


In this case, the electrolyte we are using is molten Sodium Chloride . The ions present in the electrolyte include

Cation: Sodium ions
Anion: Chloride ions

When a sodium ion touches the cathode, an electron jumps off the electrode to the ion, hence the ion becomes a Sodium atom

Na+(l) + e- --> Na (l)

At the anode, when a chloride ion touches the anode, it will lose an electron to the anode which flows through the wire and back to the battery.
This forms a Chlorine atom which then combines to another chlorine atom to form a stable simple molecular structure in the form of chlorine gas.

2Cl-(l) --> Cl2(g) + 2e-

HENCE, the sodium ions and chloride ions are said to be DISCHARGED at the electrodes.

Observations:

At the anode, effervescence of green-yellow pungent gas is observed

At the cathode, silver globules are found on the surface of water

The following video shows how the Sodium metal obtained looks like. Also, the gas produced is Chlorine gas.
The electrolyte used is molten NaCl.
Bonus: Included is also what happens when Sodium comes in contact with water (: