Specific Heat

Abstract:

Electrochemical equivalent can be easily determined by using Copper voltmeter. The equivalent mass of copper is determined based on change in the mass of a copper electrode. The electrochemical equivalent of copper is found to be 4.49×10-4 with an error of 26.7%.

Introduction:

 An electrochemical equivalent (ECE) is the amount of a substance in grams produced or consumed by the passage of one coulomb of electricity in an electrochemical reaction. A voltmeter is used to measure the electrochemical equivalent of an element. ECE is mainly used for determining the kinetics of corrosion rates and to estimate the oxidizing power in specific environments. [1]

ECE can be explained by using Faraday’s first law, which states, the mass of ions liberated at the electrodes during an electrolysis directly proportional to the quantity of electricity passing through an electrolyte. The ECE of a metal is equal to the gram-molecular mass of this substance divided by the current flow for a specific time. [2]

So by knowing the mass, flow of current and time ECE can be determined using a copper voltmeter and an ammeter. In order to determine the electrochemical equivalent for copper we use copper voltmeter, in which the aqueous solution of copper Sulphate is electrolyzed.

Theory:

Electrolyte in an electric field

At the moment when the electric field is applied to the electrolyte, e.g. through dipping the electrodes connected with the voltage source, electrostatic forces start to act on ions. These forces cause cations (positive ions) to move to the negative electrode (cathode), and anions to move to the positive electrode (anode). This phenomenon is an arranged movement of electric charges, so current is flowing in the electrolyte. Due to the bases of electrotechnics the direction of current is same as the direction of the movement of cations. The whole of phenomena occurring in electrolyte during the flow of current is called electrolysis.

In our practice electrolyte is water solution of copper sulfate. When ions reach electrodes they precipitate on them or react with the solvent. If we use coal of platinum electrodes, the reactions are as follows:

[pic 1]

On the anode a layer of metallic copper will be isolated, and around the anode – oxygen. If we use copper electrodes then the reaction will follow similarly, only on the anode a particle CuSO4 will create, as the reaction of secondary SO4 with electrode’s copper. The concentration of the solution will not change. The only change will be diminished mass of the anode and increased mass of the cathode. This reaction can be written down as follows: