A non-spontaneous reaction is one that does not occur naturally under standard conditions, meaning it requires an input of external energy to proceed. This is where electrolysis comes into play, allowing non-spontaneous reactions to occur by supplying electrical energy.
Electrolysis is a process in which electrical energy is used to drive a chemical reaction that would not occur spontaneously. This process takes place in an electrolytic cell, which consists of:
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Two electrodes: The anode (positive electrode) and cathode (negative electrode).
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Electrolyte: A solution or molten substance that contains free ions that conduct electricity.
In an electrolytic cell, when a direct current (DC) is applied, electrons flow from the power source through the external circuit, entering the anode. This causes oxidation at the anode and reduction at the cathode, resulting in a chemical reaction.
For a non-spontaneous reaction to occur:
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Sufficient voltage must be applied across the electrodes. This voltage must overcome the potential energy barrier of the non-spontaneous reaction, known as the electrolytic potential.
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The applied electric current forces the movement of ions in the electrolyte, causing oxidation at the anode (loss of electrons) and reduction at the cathode (gain of electrons).
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For example, the electrolysis of water requires a voltage of around 1.23 V to split water into hydrogen and oxygen, even though the reaction is not spontaneous at standard conditions.
In summary, by providing the necessary electrical energy to the system, a non-spontaneous reaction can be forced to occur in an electrolytic cell.