The device in which chemical energy is converted into electrical energy is called galvanic cell or electrochemical cell or voltaic cell. In a galvanic cell, a redox reaction is carried out in an indirect manner and the decrease in free energy during the chemical process appears as electrical energy. An indirect redox reaction is such that reduction and oxidation process are carried out in separate vessels. In order to understand this phenomenon, let us consider the Zn-CuS04 reaction as the basis of the cell reaction.
In its simple form, a zinc strip is dipped in the ZnSO4 solution and a copper strip is dipped in the CuSO4 solution taken in separate beakers. The two metallic strips which act as electrodes are connected by the conducting wires through a voltmeter. The two solutions are joined by an inverted U-tube known as salt bridge. The U-tube is filled with the solution of some electrolyte such as KCL, KNO3 or NH4CL to which gelatin or agar-agar has been added to convert it into semi solid paste. A schematic diagram of this cell has been shown.
The deflection in voltmeter indicates that there is a potential difference between the two electrodes. It has been found that the conventional current flows through the outer circuit from copper to zinc strip. It implies that the electrons flow occurs from zinc to copper strip.
Let us know understand working of the cell.
1. Zinc undergoes oxidation to form zinc Ions
Zn2+ + 2 e−
Zn: E0 = −0.76 V (Oxidation)
2. The electrons liberated during oxidation are pushed through the connecting wires to copper strip.
3. Copper ions move towards copper strip, puck up the electrons, and get reduced to copper atoms which are deposited at the copper strip.
Cu2+ + 2 e− Cu: E0 = +0.34 V (Reduction)
Thus the overall reaction is:
The electrode at which oxidation occurs is anode and that at which reduction occurs is cathode. In the above cell , zinc strip is anode and the copper strip is cathode.Thus in the electrochemical reaction, anode electrode acts as negative terminal and cathode electrode acts as positive terminal.
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In its simple form, a zinc strip is dipped in the ZnSO4 solution and a copper strip is dipped in the CuSO4 solution taken in separate beakers. The two metallic strips which act as electrodes are connected by the conducting wires through a voltmeter. The two solutions are joined by an inverted U-tube known as salt bridge. The U-tube is filled with the solution of some electrolyte such as KCL, KNO3 or NH4CL to which gelatin or agar-agar has been added to convert it into semi solid paste. A schematic diagram of this cell has been shown.
The deflection in voltmeter indicates that there is a potential difference between the two electrodes. It has been found that the conventional current flows through the outer circuit from copper to zinc strip. It implies that the electrons flow occurs from zinc to copper strip.
Let us know understand working of the cell.
1. Zinc undergoes oxidation to form zinc Ions
Zn2+ + 2 e−
Zn: E0 = −0.76 V (Oxidation)2. The electrons liberated during oxidation are pushed through the connecting wires to copper strip.
3. Copper ions move towards copper strip, puck up the electrons, and get reduced to copper atoms which are deposited at the copper strip.
Cu2+ + 2 e−
Cu: E0 = +0.34 V (Reduction)Thus the overall reaction is:
- Cu2+ + Zn
The electrode at which oxidation occurs is anode and that at which reduction occurs is cathode. In the above cell , zinc strip is anode and the copper strip is cathode.Thus in the electrochemical reaction, anode electrode acts as negative terminal and cathode electrode acts as positive terminal.
More :
Salt Bride and its functions
Details of Galvanic Cells
Galvanic Cells Game
Related Video :
Related Posts :
10th Grade Chemistry Projects
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