electrolysis and electroplating

The chemical and physical properties of

elements and compounds are exploited to make useful and/or aesthetic products.

Describe and explain the purification of copper by electrolysis, including a simple diagram of the cell.

Exam Objectives

Electroplating is used to

coat a thin layer of one metal on top of another.

This can be done to protect against corrosion, or to improve the appearance of an object. Sometimes a thin layer of an expensive metal can be coated onto a much cheaper one.

Electroplating

In this situation, the part to be plated on is

connected to the negative terminal (cathode) and the metal you wish to use for plating is the positive terminal (anode)

A power supply supplies a direct current to the anode, oxidizing the metal atoms that comprise it and allowing them to dissolve in the solution.

At the cathode, the dissolved metal ions in the electrolyte solution are reduced at the interface between the solution and the cathode, such that they "plate out" onto the cathode.

Nickel Plating of Copper

Electroplating copper –

acidified copper sulphate solution with a copper anode and cathode.

Technique would be used to improve brass by plating it with copper

You make electrode on to which you want to deposit copper the anode

Electroplating with copper

Cu2+(aq) + 2 e- Cu(s) cathode Cu(s) Cu2+(aq) + 2 e- anode

Half-equations represent what is happening at each electrode. In today’s practical, both electrodes contained copper of some kind.

The cathode is so called because it attracts cations – it is negatively charged

The anode attracts anions, making it positively charged

Half-equations

C3.4_7c C3.4_8b Chemistry for you: Read from page 100 Answer questions 1-10 on page 116

Questions