To understand the electrolysis of copper sulfate solution and the changes observed during the process, let's break down the question step by step. ### Correct Option: D **The bulb lights and copper is deposited at the cathode and disappears from the anode.** ### Explanation of the Correct Answer 1. **Electrolysis Basics**: Electrolysis is a process that uses electricity to drive a non-spontaneous chemical reaction. In this case, we are electrolyzing copper sulfate (CuSO₄) solution, which contains copper ions (Cu²⁺) and sulfate ions (SO₄²⁻). 2. **Electrodes**: In an electrolytic cell, there are two electrodes: - **Cathode**: The negative electrode where reduction occurs (gain of electrons). - **Anode**: The positive electrode where oxidation occurs (loss of electrons). 3. **Ionic Movement**: When an electric current is passed through the copper sulfate solution: - **Cu²⁺ ions** migrate towards the cathode (negative electrode) because they are positively charged and are attracted to the negative charge. - **SO₄²⁻ ions** migrate towards the anode (positive electrode) because they are negatively charged and are attracted to the positive charge. 4. **Reactions at the Electrodes**: - **At the Cathode**: The Cu²⁺ ions gain electrons (reduction) and are deposited as solid copper (Cu). \[ \text{Cu}^{2+} + 2e^- \rightarrow \text{Cu (s)} \] - **At the Anode**: The sulfate ions (SO₄²⁻) do not undergo oxidation directly. Instead, water (H₂O) is oxidized to produce oxygen gas (O₂) and hydrogen ions (H⁺). \[ 2\text{H}_2\text{O} \rightarrow \text{O}_2 + 4\text{H}^+ + 4e^- \] 5. **Observations**: - The bulb lights up because the electric current is flowing through the circuit, indicating that the electrolysis is occurring. - Copper is deposited at the cathode as solid copper metal. - As copper is deposited at the cathode, the concentration of Cu²⁺ ions in the solution decreases, leading to the appearance of copper disappearing from the anode (if it were a copper electrode). ### Why Other Options Are Incorrect - **Option A**: "The bulb lights and copper is deposited at both electrodes." - This is incorrect because copper is only deposited at the cathode, not at the anode. At the anode, oxygen is produced instead. - **Option B**: "The bulb lights and copper is deposited at the anode and disappears from the cathode." - This is incorrect because copper is deposited at the cathode, not the anode. The anode is where oxidation occurs, leading to the production of oxygen gas. - **Option C**: "The bulb lights and copper is deposited at the cathode and oxygen liberated at the anode." - While this statement is partially correct (copper is deposited at the cathode and oxygen is liberated at the anode), it does not fully capture the observation of copper disappearing from the anode, which is a key part of the process. ### Summary of Key Points - Electrolysis of copper sulfate solution involves the movement of Cu²⁺ ions to the cathode and SO₄²⁻ ions to the anode. - At the cathode, Cu²⁺ ions are reduced to solid copper, while at the anode, water is oxidized to produce oxygen gas. - The bulb lights up, indicating that current is flowing through the circuit. - The correct observation is that copper is deposited at the cathode and disappears from the anode. ### Revision Summary - Electrolysis involves the movement of ions towards electrodes based on charge. - Reduction occurs at the cathode (copper deposition), and oxidation occurs at the anode (oxygen production). - The bulb lighting indicates current flow, confirming the electrolysis process. - The correct observation is that copper is deposited at the cathode and disappears from the anode.