Electrolysis Investigation

Electrolysis Investigation

Aim

To investigate how voltage affects the amount of a copper (Cu)

deposited during electrolysis of copper sulphate solution (CuSO4).

Variables

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TEMPERATURE - Approximately 20° centigrade.The higher the temperature,

the faster the ions move through the solution. Thus, more copper is

deposited in the given time period.

ELECTROLYTE (CONCENTRATION) - 100g per litre. The denser the solution,

the slower the reaction. The slower the reaction, the less copper is

deposited in the given time period.

VOLTAGE - (Input / Key Variable) 1-5 volts. The higher the voltage,

the faster the ions move. The faster ions move, the more copper is

deposited in the given time period.

TIME - 1 minute. The longer the ions have to move, the more copper is

deposited.

ELECTRODES (AREA) - 211.2cm³. The larger the electrode, the more

copper can be deposited on it and faster.

ELECTRODES (DISTANCE APART) - 5cm. The further apart the electrodes,

the further the ions have to travel, and so it takes longer for the

copper to be deposited and the less copper can be deposited in the

given time period.

Prediction

I predict that the higher the voltage, the faster the ions in the

copper sulphate solution will move and so deposit more copper at the

cathode in the given time period. If I decrease the voltage less

copper will be deposited. Below is some scientific theory to back up

my prediction.

Scientific Theory

Electrolysis is the process of decomposing compounds by electrical

energy. An element is produced at each electrode. In my experiment the

copper sulphate will start to decompose. At the cathode copper will be

formed. Oxygen will be formed at the anode. This causes the anode to

wear away while the cathode gains mass.

According to Faraday's second law of electrolysis, "The quantity of a

substance that is electrolysed is proportional to the quantity of the

electricity used." It follows that the speed at which a substance is