Laboratory Activity 1H (Purification of Metals by Electrolysis):
Aim: To study the purification of copper by electrolysis.
Materials: 1.0 mol dm−3 of copper(II) nitrate, Cu(NO3)2 solution, impure copper plate and pure copper plate.
Apparatus: Beaker, battery, connecting wires with crocodile clips, ammeter and switch.
Procedure:
1. Pour 1.0 mol dm−3 of copper(II) nitrate, Cu(NO3)2 solution into a beaker until half full.
2. Connect the pure copper plate to the negative terminal of the battery and the impure copper plate to the positive terminal of the battery as shown in Figure 1.34.
3. Turn on the switch and let the electricity flow for 30 minutes.
4. Record the changes at the anode and cathode in the following table and complete the table.
Results:
Discussion:
1. Is purification process of copper a redox reaction? Explain your answer.
2. Is there any colour change to the copper(II) nitrate, Cu(NO3)2 solution? Explain your answer.
3. Impurities only form under the anode and not under the cathode. Give a reason.
4. Write the conclusion for this experiment
Answer:
1. Yes. Oxidation reaction occurs at the impure copper plate (anode) when copper atoms lose electrons to form Cu2+ ions and reduction reaction occurs at the pure copper plate (cathode) when Cu2+ ions gain electrons to form copper atoms.
2. The blue colour of copper(II) nitrate solution remains unchanged because the concentration of Cu2+ ions remains unchanged. The discharge rate of Cu2+ ions at the cathode is the same as the ionisation rate of copper atoms at the anode.
3. The anode is impure copper that contains impurities. When the impure copper ionises and dissolves, the impurities form under the anode. The cathode is pure copper that does not have impurities.
4. The purification of copper metal is carried out through an electrolysis process.
Aim: To study the purification of copper by electrolysis.
Materials: 1.0 mol dm−3 of copper(II) nitrate, Cu(NO3)2 solution, impure copper plate and pure copper plate.
Apparatus: Beaker, battery, connecting wires with crocodile clips, ammeter and switch.
Procedure:
1. Pour 1.0 mol dm−3 of copper(II) nitrate, Cu(NO3)2 solution into a beaker until half full.
2. Connect the pure copper plate to the negative terminal of the battery and the impure copper plate to the positive terminal of the battery as shown in Figure 1.34.
3. Turn on the switch and let the electricity flow for 30 minutes.
4. Record the changes at the anode and cathode in the following table and complete the table.
Results:
Discussion:
1. Is purification process of copper a redox reaction? Explain your answer.
2. Is there any colour change to the copper(II) nitrate, Cu(NO3)2 solution? Explain your answer.
3. Impurities only form under the anode and not under the cathode. Give a reason.
4. Write the conclusion for this experiment
Answer:
1. Yes. Oxidation reaction occurs at the impure copper plate (anode) when copper atoms lose electrons to form Cu2+ ions and reduction reaction occurs at the pure copper plate (cathode) when Cu2+ ions gain electrons to form copper atoms.
2. The blue colour of copper(II) nitrate solution remains unchanged because the concentration of Cu2+ ions remains unchanged. The discharge rate of Cu2+ ions at the cathode is the same as the ionisation rate of copper atoms at the anode.
3. The anode is impure copper that contains impurities. When the impure copper ionises and dissolves, the impurities form under the anode. The cathode is pure copper that does not have impurities.
4. The purification of copper metal is carried out through an electrolysis process.