• Electrolysis is the decomposition of an electrolyte using electrical energy
• Electrolyte is a substance that conducts electricity and undergoes chemical change
• Anode is the positive electrode (where oxidation occurs)
• Cathode is the negative electrode (where reduction occurs)

Objective

To purify impure copper using electrolysis.

Materials Required

• Impure copper plate (anode)
• Pure copper rod (cathode)
• Copper(II) sulphate solution (electrolyte)
• Power source (3V or 6V battery)
• Connecting wires with clips
• Beaker (250 mL)
• Ammeter and voltmeter

Procedure

1. Set up the circuit: Connect the impure copper plate to the positive terminal (anode) and the pure copper rod to the negative terminal (cathode).
2. Prepare the electrolyte: Pour copper(II) sulphate solution into the beaker.
3. Immerse electrodes: Submerge both electrodes in the electrolyte about 3-4 cm deep, ensuring they do not touch.
4. Apply current: Switch on the power supply and observe the ammeter reading (typically 1-2 amperes).
5. Observe: Leave for 15-20 minutes and observe changes at both electrodes.

Expected Observations

• At the anode (impure copper): The impure copper gradually dissolves. Impurities fall to the bottom as sludge.
• At the cathode (pure copper): Pure copper deposits onto the pure copper rod, increasing its mass.
• The electrolyte: Remains blue as copper ions are transferred from anode to cathode.

Working Principle

During electrolysis, copper atoms at the anode lose electrons (oxidation) and enter the solution as Cu²⁺ ions:

$\text{Cu} \rightarrow \text{Cu}^{2+} + 2e^-$

These ions move through the solution and deposit at the cathode by gaining electrons (reduction):

$\text{Cu}^{2+} + 2e^- \rightarrow \text{Cu}$

Impurities either dissolve or settle as sludge below the anode.

Objective

To coat a metal object with another metal (e.g., copper plating on iron) to prevent corrosion.

Materials Required

• Iron plate or nail (object to be plated)
• Copper sheet (anode - plating metal)
• Copper(II) sulphate solution or suitable electrolyte
• Power source (3V battery)
• Connecting wires
• Beaker (250 mL)
• Sandpaper (for cleaning surfaces)
• Distilled water

Procedure

1. Clean the surface: Use sandpaper to remove rust and dirt from the iron plate. Rinse with distilled water.
2. Set up: Connect the iron plate to the negative terminal (cathode) and copper sheet to the positive terminal (anode).
3. Prepare electrolyte: Place copper(II) sulphate solution in the beaker.
4. Immerse electrodes: Submerge both electrodes in the solution without touching.
5. Electroplating: Switch on and maintain current for 10-15 minutes.
6. Finish: Remove the plated object, rinse with distilled water, and dry carefully.

Expected Results

The iron surface becomes coated with a thin, reddish-brown layer of copper. This coating:

• Protects iron from rusting
• Improves appearance
• Acts as a barrier against moisture and oxygen

Why Electroplating Inhibits Corrosion

When a more reactive metal (like zinc) is plated onto iron, it sacrificially protects the iron. Zinc oxidizes instead of iron:

$\text{Zn} \rightarrow \text{Zn}^{2+} + 2e^-$

This is called sacrificial anode protection. For decorative purposes, less reactive metals like copper or nickel are used.

• Purification: Uses impure metal as anode, pure metal as cathode; impurities settle as sludge
• Electroplating: Object to be protected is the cathode; plating metal is the anode
• Both processes require an electrolyte and direct current
• Electroplating prevents corrosion by acting as a physical barrier or sacrificial protection

In Tanzania, electroplating is used at workshops in cities like Dar es Salaam and Arusha to restore rusted car parts and household items. For example, a local mechanic may electroplate a corroded iron bracket with zinc or copper to extend its lifespan before selling it back to a customer — a practical application that saves money compared to buying new parts, which could cost between TSh 10,000 to TSh 50,000 depending on the item.