Determination of electrochemical equivalent of copper.

A liquid or a solution that conducts electricity is called an electrolyte; solutions like copper sulphate, sodium chloride and silver nitrate are common examples of electrolytes. When a current is passed through an electrolyte, chemical action takes place and it is decomposed. This is known as electrolysis.

The vessel in which electrolysis takes place is called a voltmeter. Two metal plates dipping in the electrolyte are called the electrodes. The electrode through which current enters the electrolyte is called the anode. The electrode through which current leaves the electrolyte is called the cathode.

Water voltameter

Acidified water is electrolysed in a water voltameter with platinum electrodes. Water is decomposed into hydrogen and oxygen. The electro-positive hydrogen goes to the cathode and is evolved there as gaseous hydrogen. Electronegative oxygen ion is collected at the anode.

Silver voltameter

Silver nitrate solution is an electrolyte in a silver voltameter with silver electrodes. Silver is deposited on the cathode, and the oxide goes into solution.

Copper voltameter

Copper sulphate solution is an electrolyte in a copper voltameter with copper electrodes. Copper is deposited on the cathode.

Determination of the chemical equivalent of copper

A copper voltameter consists of a glass vessel containing copper sulphate solution. Tow copper plates which form the electrodes are kept immersed in the solution. The plate connected to the positive of the battery is called the anode and that connected to the negative of the battery is called the cathode.

The copper voltameter is connected in series with a battery and key. The circuit is closed and the rheostat is adjusted so that the ammeter reads 1 ampere.

The current is then stopped. The cathode is removed, cleaned well with sandpaper, washed and dried. Its weight correct to milligram is determined by the method of vibrations. The weight plate is then replaced and the circuit is closed.

A stopped clock is immediately started. The ammeter reading is noted every 5 minutes. At the end of 30 minutes, the current is stopped. The cathode is removed, rinsed in still water and dried. Its weight is accurately determined.

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