The positively charged copper ions move toward the cathode where they gain two electrons and become copper atoms, which are deposited on the cathode, as shown below.
Cu 2 +(aq) + 2e − → Cu(s)
However, when electrolyzing aqueous CuSO4, dissolution of Cu2+ ions from the anode cannot be observed because the aqueous CuSO4 is already blue. Even the deposition of copper on the cathode is somewhat difficult to observe during the
electrolysis. Only after the electrolysis, students can observe the change of weight or shape of the anode and cathode. Therefore, students find it difficult to understand what is happening in electrolysis at the microscopic level although the schematic diagrams are effective at helping them to imagine what is going on.
If the students can visually observe the dissolution of Cu2+ ions from the copper electrode, the migration of ions, and the deposition of copper on the cathode, they can understand what is happening in electrolysis at the microscopic level intuitively. Therefore, in this demonstration, a colorless and transparent electrolyte solution is used. Sodium polyacrylate is used as the electrolyte for two reasons: (i) it is colorless and (ii) it forms a gel that prevents the copper ions from diffusing freely and rapidly through the solution. As a result, the dissolution of Cu2+ ions from the Cu anode, the migration of Cu2+ ion in the electrolyte solution, and the deposition of Cu on the cathode are observed visually. The time needed for this demonstration is about 15 min. Showing this demonstration to the students will help them understand what is happening in electrolysis at the microscopic level.