Galvanic Cell Construction

CONTENTS

1. Introduction

2. Aim and objectives

3. Methodology

4. Results and discussion

5. Conclusion

1. Introduction:

A galvanic cell, named after Luigi Galvani, is an electrochemical cell that derives electrical energy from spontaneous redox reactions taking place within the cell. It generally consists of two different metals connected by a salt bridge, or individual half-cells separated by a porous membrane.

Volta was the inventor of the voltaic pile, the first electrical battery. In common usage, the word "battery" has come to include a single galvanic cell, but a battery properly consists of multiple cells.

In its simplest form, a half-cell consists of a solid metal (called an electrode) that is submerged in a solution; the solution contains cations of the electrode metal and anions to balance the charge of the cations. In essence, a half-cell contains a metal in two oxidation states; inside an isolated half-cell, there is an oxidation-reduction (redox) reaction that is in chemical equilibrium, a condition written symbolically as follows:

Mⁿ⁺ (oxidized) + ne⁻ ⇌ M (reduced)

A galvanic cell consists of two half-cells, such that the electrode of one half-cell is composed of metal A, and the electrode of the other half-cell is composed of metal B; the redox reactions for the two separate half-cells are thus:

Aⁿ⁺ + ne⁻ ⇌ A

B^m+ + me⁻ ⇌ B

In general, then, these two metals can react with each other:

m A + n B^m+ ⇌ n B + m Aⁿ⁺

2.  Aim and objectives:

Fabrication of salt bridge and construction of galvanic cell for Cu & Zn.

3. Methodology:

Take a 500ml beaker and full it with 250ml of 1M CuSO₄. In another 500ml beaker full 250ml of 1M ZnSO_4. In the beaker containing CuSO₄ immerse copper plate and in beaker containing ZnSO₄ immerse zinc plate. Now prepare a salt bridge to create a medium between solutions. Take few amount of NaCl and dissolve it in water. Soak a cloth in NaCl solution. Connect the half cells by salt bridge. When multimeter is connected in between Zinc and Copper plate some potential difference is observed.

Zinc Half Cell:

The anode(Zinc) is the electrode where oxidation (loss of electrons) takes place; in a galvanic cell, it is the negative electrode, as when oxidation occurs, electrons are left behind on the electrode. These electrons then migrate to the cathode (positive electrode). However, in electrolysis, an electric current stimulates electron flow in the opposite direction. Thus, the anode is positive, The zinc electrode is the anode.

Zn à Zn²⁺ + 2e^-

Copper Half Cell:

The cathode(copper) is the electrode where reduction (gain of electrons) takes place; in a galvanic cell, it is the positive electrode, as less oxidation occurs, fewer ions go into solution, and less electrons are left on the electrode. Instead, there is a greater tendency for aqueous ions to be reduced by the incoming electrons from the anode. However, in electrolysis, the cathode is the negative terminal, and attracting positive ions from the solution. The copper electrode is the cathode.

Cu²⁺ + 2e^- à Cu

Copper readily oxidizes zinc; for the Galvanic cell depicted in the figure, the anode is zinc and the cathode is copper, and the anions in the solutions are sulphates of the respective metals. When an electrically conducting device connects the electrodes, the electrochemical reaction is:

Zn + Cu²⁺ → Zn²⁺+ Cu

The zinc electrode is dissolved and copper is deposited on the copper electrode.

Galvanic cells are typically used as a source of electrical power. By their nature, they produce direct current.

4. Results and discussion:

The obtained results of Galvanic cell are given in table below with different concentrations of Solutions.

Concentration of CuSO4	Concentration of ZnSO4	Voltage Obtained
1M CuSO4	1M ZnSO4	1.08V
0.01M CuSO4	0.01M ZnSO4	0.81V
0.01M CuSO4	1M ZnSO4	0.7V
1M CuSO4	0.01M ZnSO4	1.01V

According to the theoretically calculated valve the maximum obtained voltage for 1M CuSO₄ and 1M ZnSO₄ should be 1.1V. But in our project we got a maximum voltage of 1.08V this may be due to some impurities present in solutions and corrosion of zinc and copper plates.

5. Conclusion:

By this project we became familiar with various concepts such as solutions by way of dissolved ions. We have observed redox reactions at work, and that they can be