A student investigated the electrolysis of green copper chromate solution. Figure 4 shows the apparatus and Figure 5 shows the results.
Copper chromate solution contains the ions Cu²⁺ and CrO₄²⁻.
Explain the results shown in Figure 5.

The experiment demonstrates the migration of ions during electrolysis. 1. The copper chromate solution initially appears green because it is a mixture of blue Cu²⁺ ions and yellow CrO₄²⁻ ions. 2. When the power supply is turned on, an electric field is created. 3. The copper ions (Cu²⁺) are positively charged. They are attracted to the negative electrode (cathode). This causes the blue colour to move towards the negative electrode. 4. The chromate ions (CrO₄²⁻) are negatively charged. They are attracted to the positive electrode (anode). This causes the yellow colour to move towards the positive electrode. This separation of colours is direct evidence that ionic solutions contain mobile, charged particles (ions).