5 (a) Some metal objects are electroplated to improve their appearance - Edexcel - GCSE Chemistry - Question 5 - 2014 - Paper 1

During electrolysis, the impure copper anode loses mass as copper ions dissolve into the solution and migrate towards the pure copper cathode. This occurs because copper ions from the anode oxidize and enter the solution, while at the cathode, copper ions from the solution are reduced and deposited as pure copper.

1. Anode Process: The impure copper anode loses mass as copper atoms lose electrons, becoming copper ions that enter the solution. This is represented by the equation:

   $$$$

ightarrow ext{Cu}^{2+} + 2e^-$$

2. Cathode Process: At the cathode, copper ions gain electrons and are deposited onto the cathode, resulting in an increase in mass:

   $$$$

ightarrow ext{Cu(s)}$$

3. Mass Changes: The change in mass for the impure copper anode is a decrease of 5.0 g, while the pure copper cathode's mass increases by 4.8 g. This indicates that copper is effectively transferred from the anode to the cathode, demonstrating the principles of electrolysis.