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Question
How many moles of electrons are required for reduction of 2 moles of Zn2+ to Zn?
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Solution
The balanced equation for the reduction of Zn2+ to Zn is
\[\ce{Zn^{2+}_{ (aq)} + 2e- -> Zn_{(s)}}\]
The equation shows that 1 mole of Zn2+ is reduced to Zn by 2 moles of electrons.
For reduction of 2 moles of Zn2+, 4 moles of electrons will be required.
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Oxidation-reduction reactions are commonly known as redox reactions. They involve transfer of electrons from one species to another. In a spontaneous reaction, energy is released which can be used to do useful work. The reaction is split into two half-reactions. Two different containers are used and a wire is used to drive the electrons from one side to the other and a Voltaic/Galvanic cell is created. It is an electrochemical cell that uses spontaneous redox reactions to generate electricity. A salt bridge also connects to the half-cells. The reading of the voltmeter gives the cell voltage or cell potential or electromotive force. If \[\ce{E^0_{cell}}\] is positive the reaction is spontaneous and if it is negative the reaction is non-spontaneous and is referred to as electrolytic cell. Electrolysis refers to the decomposition of a substance by an electric current. One mole of electric charge when passed through a cell will discharge half a mole of a divalent metal ion such as Cu2+. This was first formulated by Faraday in the form of laws of electrolysis.
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