Electrolytic Refining
Class 10 Science | Metals and Non-metals | CBSE + Foundation + Competitive
⚡ Electrolytic Refining / विद्युत अपघटनी परिष्करण
1. What is Electrolytic Refining? / विद्युत अपघटनी परिष्करण क्या है?
English:
Electrolytic refining is a method used to obtain a very pure metal from an impure metal by using electrolysis. In this process, the impure metal is made the anode, a thin sheet of pure metal is made the cathode, and a suitable solution of the metal salt is used as the electrolyte. When electric current is passed through the electrolyte, metal from the impure anode dissolves into the solution and an equal amount of pure metal gets deposited on the cathode.
हिन्दी:
विद्युत अपघटनी परिष्करण वह विधि है जिसमें विद्युत अपघटन द्वारा अशुद्ध धातु से बहुत अधिक शुद्धता वाली धातु प्राप्त की जाती है। इस प्रक्रिया में अशुद्ध धातु को एनोड, शुद्ध धातु की पतली पट्टी को कैथोड तथा धातु के उपयुक्त लवण के विलयन को विद्युत अपघट्य (Electrolyte) बनाया जाता है। जब विद्युत धारा प्रवाहित की जाती है, तो अशुद्ध एनोड से धातु विलयन में चली जाती है और उतनी ही मात्रा में शुद्ध धातु कैथोड पर जमा होती है।
Electrolytic refining is a method used to obtain a very pure metal from an impure metal by using electrolysis. In this process, the impure metal is made the anode, a thin sheet of pure metal is made the cathode, and a suitable solution of the metal salt is used as the electrolyte. When electric current is passed through the electrolyte, metal from the impure anode dissolves into the solution and an equal amount of pure metal gets deposited on the cathode.
हिन्दी:
विद्युत अपघटनी परिष्करण वह विधि है जिसमें विद्युत अपघटन द्वारा अशुद्ध धातु से बहुत अधिक शुद्धता वाली धातु प्राप्त की जाती है। इस प्रक्रिया में अशुद्ध धातु को एनोड, शुद्ध धातु की पतली पट्टी को कैथोड तथा धातु के उपयुक्त लवण के विलयन को विद्युत अपघट्य (Electrolyte) बनाया जाता है। जब विद्युत धारा प्रवाहित की जाती है, तो अशुद्ध एनोड से धातु विलयन में चली जाती है और उतनी ही मात्रा में शुद्ध धातु कैथोड पर जमा होती है।
2. Electrolytic Refining of Copper / तांबे का विद्युत अपघटनी परिष्करण
English:
Copper obtained from extraction processes contains impurities such as iron, zinc, silver, gold and other substances. To obtain highly pure copper, electrolytic refining is carried out. The arrangement consists of:
निष्कर्षण द्वारा प्राप्त तांबे में लोहे, जिंक, चांदी, सोना आदि की अशुद्धियाँ हो सकती हैं। अधिक शुद्ध तांबा प्राप्त करने के लिए विद्युत अपघटनी परिष्करण किया जाता है। इसमें:
Copper obtained from extraction processes contains impurities such as iron, zinc, silver, gold and other substances. To obtain highly pure copper, electrolytic refining is carried out. The arrangement consists of:
- Anode: Impure copper plate
- Cathode: Thin sheet of pure copper
- Electrolyte: Acidified copper sulphate (CuSO₄) solution
- Power supply: Direct current (DC)
निष्कर्षण द्वारा प्राप्त तांबे में लोहे, जिंक, चांदी, सोना आदि की अशुद्धियाँ हो सकती हैं। अधिक शुद्ध तांबा प्राप्त करने के लिए विद्युत अपघटनी परिष्करण किया जाता है। इसमें:
- एनोड: अशुद्ध तांबे की प्लेट
- कैथोड: शुद्ध तांबे की पतली पट्टी
- विद्युत अपघट्य: अम्लीकृत CuSO₄ विलयन
- विद्युत धारा: Direct Current (DC)
3. Working of Copper Refining / तांबे के परिष्करण की कार्यविधि
जब विद्युत धारा प्रवाहित की जाती है, तो अशुद्ध तांबे के एनोड से Cu²⁺ आयन विलयन में जाते हैं।
At the anode:
Cu → Cu²⁺ + 2e⁻
कैथोड पर Cu²⁺ आयन इलेक्ट्रॉन ग्रहण करके शुद्ध तांबे के रूप में जमा होते हैं।
At the cathode:
Cu²⁺ + 2e⁻ → Cu
इस प्रकार एनोड धीरे-धीरे घुलता जाता है और कैथोड पर शुद्ध तांबे की परत मोटी होती जाती है।
Thus: Impure copper anode becomes smaller, while the pure copper cathode becomes thicker.
4. Role of Anode, Cathode and Electrolyte / एनोड, कैथोड एवं विद्युत अपघट्य की भूमिका
| Part / भाग | Role / भूमिका |
|---|---|
| Anode / एनोड | Impure copper is connected to the positive terminal. Copper atoms lose electrons and enter the electrolyte as Cu²⁺ ions. |
| Cathode / कैथोड | Pure copper sheet is connected to the negative terminal. Cu²⁺ ions gain electrons and deposit as pure copper. |
| Electrolyte / विद्युत अपघट्य | Acidified CuSO₄ solution provides Cu²⁺ ions and allows electric current to pass through the solution. |
5. What Happens to Impurities? / अशुद्धियों का क्या होता है?
Electrolytic refining separates impurities from the metal.
Less reactive impurities such as silver and gold do not dissolve easily. They settle at the bottom of the electrolytic tank as anode mud.
More reactive impurities such as iron and zinc may dissolve into the electrolyte but generally do not get deposited on the cathode under the refining conditions.
Hindi:
कम क्रियाशील अशुद्धियाँ जैसे चांदी और सोना आसानी से विलयन में नहीं जातीं और नीचे बैठकर anode mud बनाती हैं। अधिक क्रियाशील अशुद्धियाँ जैसे आयरन और जिंक विलयन में जा सकती हैं, लेकिन सामान्यतः कैथोड पर जमा नहीं होतीं।
Hindi:
कम क्रियाशील अशुद्धियाँ जैसे चांदी और सोना आसानी से विलयन में नहीं जातीं और नीचे बैठकर anode mud बनाती हैं। अधिक क्रियाशील अशुद्धियाँ जैसे आयरन और जिंक विलयन में जा सकती हैं, लेकिन सामान्यतः कैथोड पर जमा नहीं होतीं।
6. Important Equations / महत्वपूर्ण समीकरण
At Anode: Cu → Cu²⁺ + 2e⁻
At Cathode: Cu²⁺ + 2e⁻ → Cu
Overall: Copper is transferred from impure anode to pure cathode.
7. Flow of Copper During Refining / तांबे का प्रवाह
Impure Copper Anode → Cu²⁺ ions in Electrolyte → Pure Copper Cathode
Exam Point:
In electrolytic refining of copper:
Anode = Impure copper
Cathode = Pure copper
Electrolyte = Acidified CuSO₄ solution
Impurities like Ag and Au → Anode mud
In electrolytic refining of copper:
Anode = Impure copper
Cathode = Pure copper
Electrolyte = Acidified CuSO₄ solution
Impurities like Ag and Au → Anode mud
8. 30 MCQs / बहुविकल्पीय प्रश्न
Q1. What is the main purpose of electrolytic refining?
विद्युत अपघटनी परिष्करण का मुख्य उद्देश्य क्या है?
विद्युत अपघटनी परिष्करण का मुख्य उद्देश्य क्या है?
A. To purify a metal
B. To convert metal into ore
C. To make an alloy
D. To produce non-metal
Answer: A — Electrolytic refining is used to obtain highly pure metal.
Q2. In copper refining, the anode is made of:
तांबे के परिष्करण में एनोड किसका बना होता है?
तांबे के परिष्करण में एनोड किसका बना होता है?
A. Pure copper
B. Impure copper
C. Zinc
D. Iron
Answer: B
Q3. The cathode in copper refining is:
तांबे के परिष्करण में कैथोड होता है:
तांबे के परिष्करण में कैथोड होता है:
A. Impure copper
B. Graphite
C. Thin sheet of pure copper
D. Zinc sheet
Answer: C
Q4. Which electrolyte is used in electrolytic refining of copper?
A. NaCl solution
B. Acidified CuSO₄ solution
C. NaOH solution
D. HCl only
Answer: B
Q5. At the anode, copper undergoes:
A. Reduction
B. Oxidation
C. Neutralisation
D. Combustion
Answer: B — Cu loses electrons at the anode.
Q6. Which reaction occurs at the cathode?
A. Cu → Cu²⁺ + 2e⁻
B. Cu²⁺ + 2e⁻ → Cu
C. Cu + 2e⁻ → Cu²⁺
D. Cu²⁺ → Cu³⁺
Answer: B
Q7. The anode is connected to the:
A. Negative terminal
B. Positive terminal
C. Neutral terminal
D. Earth terminal
Answer: B
Q8. The cathode is connected to the:
A. Positive terminal
B. Neutral terminal
C. Negative terminal
D. AC terminal only
Answer: C
Q9. Which impurities may form anode mud?
A. Gold and silver
B. Sodium and potassium
C. Calcium and magnesium
D. Hydrogen and oxygen
Answer: A
Q10. Copper ions in the electrolyte move towards the:
A. Anode
B. Cathode
C. Salt bridge
D. Container wall
Answer: B
Q11. During copper refining, the mass of the anode generally:
A. Increases
B. Remains unchanged
C. Decreases
D. Becomes zero instantly
Answer: C
Q12. During copper refining, the mass of the cathode:
A. Increases
B. Decreases
C. Remains zero
D. Always remains unchanged
Answer: A
Q13. Copper atoms at the anode lose:
A. Protons
B. Neutrons
C. Electrons
D. Nuclei
Answer: C
Q14. Cu²⁺ ions gain electrons at the:
A. Anode
B. Cathode
C. Electrolyte surface
D. Salt bridge
Answer: B
Q15. The process at the cathode is:
A. Oxidation
B. Reduction
C. Combustion
D. Sublimation
Answer: B
Q16. What is anode mud?
A. Pure copper deposited at cathode
B. Insoluble valuable impurities collected below the anode
C. Electrolyte
D. Copper sulphate crystals
Answer: B
Q17. Which metal is commonly refined electrolytically?
A. Copper
B. Sodium chloride
C. Sulphur
D. Carbon
Answer: A
Q18. Which ion is mainly responsible for deposition of copper?
A. Na⁺
B. Cl⁻
C. Cu²⁺
D. SO₄²⁻
Answer: C
Q19. Acidified CuSO₄ is used as:
A. Anode
B. Cathode
C. Electrolyte
D. Insulator
Answer: C
Q20. Which statement is correct?
A. Pure copper is used as anode
B. Impure copper is used as anode
C. Copper ions are oxidised at cathode
D. Gold dissolves completely into solution
Answer: B
Q21. The reaction Cu → Cu²⁺ + 2e⁻ represents:
A. Oxidation
B. Reduction
C. Neutralisation
D. Precipitation
Answer: A
Q22. The reaction Cu²⁺ + 2e⁻ → Cu represents:
A. Oxidation
B. Reduction
C. Combustion
D. Roasting
Answer: B
Q23. Which of the following is a valuable impurity recovered from anode mud?
A. Gold
B. Sodium
C. Magnesium
D. Aluminium
Answer: A
Q24. Electrolytic refining is based on:
A. Electrolysis
B. Filtration
C. Distillation
D. Evaporation only
Answer: A
Q25. What happens to Cu²⁺ ions at the cathode?
A. They lose electrons
B. They gain electrons
C. They become sulphate ions
D. They form oxygen
Answer: B
Q26. Which terminal is the cathode connected to in an electrolytic cell?
A. Positive
B. Negative
C. Both terminals
D. No terminal
Answer: B
Q27. Which process occurs at the anode during copper refining?
A. Deposition of pure copper
B. Dissolution of copper
C. Formation of sodium
D. Formation of chlorine only
Answer: B
Q28. Why is the cathode made of pure copper?
A. To collect pure copper
B. To dissolve impurities
C. To produce oxygen
D. To stop current
Answer: A
Q29. Which combination is correct?
A. Anode–pure copper; Cathode–impure copper
B. Anode–impure copper; Cathode–pure copper
C. Both electrodes–zinc
D. Both electrodes–gold
Answer: B
Q30. The purity of copper increases mainly because:
A. Impurities are deposited preferentially
B. Copper selectively transfers from anode to cathode
C. Electrolyte evaporates
D. Copper burns
Answer: B
9. 30 Subjective Questions with Answers / व्यक्तिपरक प्रश्न
1 Mark
Q1. What is electrolytic refining?
विद्युत अपघटनी परिष्करण क्या है?
Q1. What is electrolytic refining?
विद्युत अपघटनी परिष्करण क्या है?
Answer: It is the process of purifying an impure metal using electrolysis.
यह विद्युत अपघटन द्वारा अशुद्ध धातु को शुद्ध करने की प्रक्रिया है।
यह विद्युत अपघटन द्वारा अशुद्ध धातु को शुद्ध करने की प्रक्रिया है।
1 Mark
Q2. What is used as the anode in copper refining?
Q2. What is used as the anode in copper refining?
Answer: Impure copper is used as the anode.
1 Mark
Q3. What is used as the cathode in copper refining?
Q3. What is used as the cathode in copper refining?
Answer: A thin sheet of pure copper.
1 Mark
Q4. Name the electrolyte used in copper refining.
Q4. Name the electrolyte used in copper refining.
Answer: Acidified copper sulphate (CuSO₄) solution.
1 Mark
Q5. What is anode mud?
Q5. What is anode mud?
Answer: Insoluble impurities such as silver and gold that settle below the anode are called anode mud.
2 Marks
Q6. State the roles of anode and cathode in copper refining.
Q6. State the roles of anode and cathode in copper refining.
Answer:
Anode: Impure copper dissolves and releases Cu²⁺ ions.
Cathode: Cu²⁺ ions gain electrons and deposit as pure copper.
Anode: Impure copper dissolves and releases Cu²⁺ ions.
Cathode: Cu²⁺ ions gain electrons and deposit as pure copper.
2 Marks
Q7. Why is acidified CuSO₄ solution used as electrolyte?
Q7. Why is acidified CuSO₄ solution used as electrolyte?
Answer: It provides Cu²⁺ ions required for copper deposition and conducts electric current through the solution.
2 Marks
Q8. Write the electrode reactions during copper refining.
Q8. Write the electrode reactions during copper refining.
At anode:
Cu → Cu²⁺ + 2e⁻
At cathode:
Cu²⁺ + 2e⁻ → Cu
Cu → Cu²⁺ + 2e⁻
At cathode:
Cu²⁺ + 2e⁻ → Cu
2 Marks
Q9. What happens to the mass of the anode and cathode?
Q9. What happens to the mass of the anode and cathode?
Answer: The mass of the impure copper anode decreases, while the mass of the pure copper cathode increases.
2 Marks
Q10. What happens to gold and silver impurities?
Q10. What happens to gold and silver impurities?
Answer: They do not dissolve readily and settle at the bottom as anode mud.
3 Marks
Q11. Explain electrolytic refining of copper.
Q11. Explain electrolytic refining of copper.
Answer:
1. Impure copper is used as anode.
2. Pure copper sheet is used as cathode.
3. Acidified CuSO₄ solution is used as electrolyte.
4. On passing current, copper dissolves from anode and deposits on cathode.
1. Impure copper is used as anode.
2. Pure copper sheet is used as cathode.
3. Acidified CuSO₄ solution is used as electrolyte.
4. On passing current, copper dissolves from anode and deposits on cathode.
3 Marks
Q12. Explain the role of anode, cathode and electrolyte.
Q12. Explain the role of anode, cathode and electrolyte.
Answer:
Anode: Impure copper dissolves into the electrolyte.
Cathode: Pure copper is deposited on it.
Electrolyte: Acidified CuSO₄ provides Cu²⁺ ions and conducts current.
Anode: Impure copper dissolves into the electrolyte.
Cathode: Pure copper is deposited on it.
Electrolyte: Acidified CuSO₄ provides Cu²⁺ ions and conducts current.
3 Marks
Q13. Differentiate between anode and cathode in copper refining.
Q13. Differentiate between anode and cathode in copper refining.
| Anode | Cathode |
|---|---|
| Impure copper | Pure copper |
| Connected to positive terminal | Connected to negative terminal |
| Copper dissolves | Copper deposits |
3 Marks
Q14. Why does copper get deposited on the cathode?
Q14. Why does copper get deposited on the cathode?
Answer: Cu²⁺ ions in the electrolyte move towards the negatively charged cathode. They gain two electrons and are converted into copper atoms:
Cu²⁺ + 2e⁻ → Cu
Cu²⁺ + 2e⁻ → Cu
3 Marks
Q15. What is the importance of anode mud?
Q15. What is the importance of anode mud?
Answer: Anode mud contains valuable less-reactive metals such as silver and gold. These metals can be recovered separately and have economic value.
4 Marks
Q16. Describe the complete electrolytic refining process of copper.
Q16. Describe the complete electrolytic refining process of copper.
Answer:
1. A large impure copper plate is connected to the positive terminal.
2. A thin pure copper sheet is connected to the negative terminal.
3. Acidified CuSO₄ solution is used as electrolyte.
4. Copper atoms from anode form Cu²⁺ ions.
5. Cu²⁺ ions move towards cathode.
6. They gain electrons and form pure copper.
7. Insoluble impurities settle as anode mud.
1. A large impure copper plate is connected to the positive terminal.
2. A thin pure copper sheet is connected to the negative terminal.
3. Acidified CuSO₄ solution is used as electrolyte.
4. Copper atoms from anode form Cu²⁺ ions.
5. Cu²⁺ ions move towards cathode.
6. They gain electrons and form pure copper.
7. Insoluble impurities settle as anode mud.
4 Marks
Q17. Write the reactions occurring at the two electrodes.
Q17. Write the reactions occurring at the two electrodes.
Anode:
Cu → Cu²⁺ + 2e⁻
Cathode:
Cu²⁺ + 2e⁻ → Cu
Copper is therefore transferred from the impure anode to the pure cathode.
Cu → Cu²⁺ + 2e⁻
Cathode:
Cu²⁺ + 2e⁻ → Cu
Copper is therefore transferred from the impure anode to the pure cathode.
4 Marks
Q18. Explain the fate of impurities during electrolytic refining.
Q18. Explain the fate of impurities during electrolytic refining.
Answer: Less reactive impurities such as gold and silver settle as anode mud. More reactive impurities such as iron and zinc may dissolve in the electrolyte but generally remain in solution instead of depositing on the cathode.
4 Marks
Q19. Why is electrolytic refining better than simple physical separation for copper?
Q19. Why is electrolytic refining better than simple physical separation for copper?
Answer: Electrolytic refining separates copper from chemically mixed impurities and produces very high-purity copper suitable for electrical applications.
4 Marks
Q20. Explain why the cathode becomes thicker during refining.
Q20. Explain why the cathode becomes thicker during refining.
Answer: Cu²⁺ ions from the electrolyte gain electrons at the cathode:
Cu²⁺ + 2e⁻ → Cu
The newly formed copper atoms deposit on the cathode, increasing its thickness and mass.
Cu²⁺ + 2e⁻ → Cu
The newly formed copper atoms deposit on the cathode, increasing its thickness and mass.
5 Marks
Q21. Explain electrolytic refining of copper with a labelled arrangement.
Q21. Explain electrolytic refining of copper with a labelled arrangement.
Answer:
The arrangement consists of an impure copper anode, pure copper cathode and acidified CuSO₄ electrolyte. Connections:
Anode → Positive terminal
Cathode → Negative terminal Anode reaction:
Cu → Cu²⁺ + 2e⁻ Cathode reaction:
Cu²⁺ + 2e⁻ → Cu Thus pure copper gets deposited on the cathode and impurities are separated.
The arrangement consists of an impure copper anode, pure copper cathode and acidified CuSO₄ electrolyte. Connections:
Anode → Positive terminal
Cathode → Negative terminal Anode reaction:
Cu → Cu²⁺ + 2e⁻ Cathode reaction:
Cu²⁺ + 2e⁻ → Cu Thus pure copper gets deposited on the cathode and impurities are separated.
5 Marks
Q22. Explain the role of all three components used in copper electrolytic refining.
Q22. Explain the role of all three components used in copper electrolytic refining.
Anode: Impure copper plate. It supplies Cu²⁺ ions to the solution.
Cathode: Thin pure copper sheet. It receives Cu²⁺ ions and becomes coated with pure copper.
Electrolyte: Acidified CuSO₄ solution. It provides Cu²⁺ ions and permits ionic conduction.
Cathode: Thin pure copper sheet. It receives Cu²⁺ ions and becomes coated with pure copper.
Electrolyte: Acidified CuSO₄ solution. It provides Cu²⁺ ions and permits ionic conduction.
5 Marks
Q23. Explain oxidation and reduction during electrolytic refining.
Q23. Explain oxidation and reduction during electrolytic refining.
Answer:
At the anode, copper loses electrons:
Cu → Cu²⁺ + 2e⁻
This is oxidation. At the cathode, Cu²⁺ ions gain electrons:
Cu²⁺ + 2e⁻ → Cu
This is reduction. Therefore oxidation occurs at the anode and reduction occurs at the cathode.
At the anode, copper loses electrons:
Cu → Cu²⁺ + 2e⁻
This is oxidation. At the cathode, Cu²⁺ ions gain electrons:
Cu²⁺ + 2e⁻ → Cu
This is reduction. Therefore oxidation occurs at the anode and reduction occurs at the cathode.
5 Marks
Q24. How does electrolytic refining help in obtaining pure copper?
Q24. How does electrolytic refining help in obtaining pure copper?
Answer: Copper from the impure anode dissolves as Cu²⁺ ions. These ions are selectively deposited as copper on the pure cathode. Less reactive impurities settle as anode mud, while many more reactive impurities remain in solution. Hence high-purity copper is obtained.
5 Marks
Q25. Give five important points about electrolytic refining of copper.
Q25. Give five important points about electrolytic refining of copper.
Answer:
1. Impure copper is the anode.
2. Pure copper is the cathode.
3. Acidified CuSO₄ is the electrolyte.
4. Copper dissolves from the anode and deposits on the cathode.
5. Gold and silver may be collected as anode mud.
1. Impure copper is the anode.
2. Pure copper is the cathode.
3. Acidified CuSO₄ is the electrolyte.
4. Copper dissolves from the anode and deposits on the cathode.
5. Gold and silver may be collected as anode mud.
6 Marks
Q26. Explain the complete mechanism of electrolytic refining of copper with equations.
Q26. Explain the complete mechanism of electrolytic refining of copper with equations.
Answer:
Step 1: Impure copper is made the anode.
Step 2: Pure copper sheet is made the cathode.
Step 3: Acidified CuSO₄ is used as electrolyte.
Step 4: At anode:
Cu → Cu²⁺ + 2e⁻
Step 5: Cu²⁺ ions move through the electrolyte towards the cathode.
Step 6: At cathode:
Cu²⁺ + 2e⁻ → Cu
Step 7: Pure copper accumulates on the cathode while impurities are separated.
Step 1: Impure copper is made the anode.
Step 2: Pure copper sheet is made the cathode.
Step 3: Acidified CuSO₄ is used as electrolyte.
Step 4: At anode:
Cu → Cu²⁺ + 2e⁻
Step 5: Cu²⁺ ions move through the electrolyte towards the cathode.
Step 6: At cathode:
Cu²⁺ + 2e⁻ → Cu
Step 7: Pure copper accumulates on the cathode while impurities are separated.
6 Marks
Q27. Describe the electrolytic refining of copper and explain the fate of impurities.
Q27. Describe the electrolytic refining of copper and explain the fate of impurities.
Answer:
Impure copper is connected to the positive terminal and pure copper to the negative terminal. Acidified CuSO₄ is used as electrolyte. Copper from the anode oxidises to Cu²⁺ ions. These ions migrate towards the cathode and are reduced to copper atoms. Less reactive impurities such as silver and gold settle at the bottom as anode mud. More reactive impurities such as iron and zinc may remain in the electrolyte. Thus high-purity copper is obtained at the cathode.
Impure copper is connected to the positive terminal and pure copper to the negative terminal. Acidified CuSO₄ is used as electrolyte. Copper from the anode oxidises to Cu²⁺ ions. These ions migrate towards the cathode and are reduced to copper atoms. Less reactive impurities such as silver and gold settle at the bottom as anode mud. More reactive impurities such as iron and zinc may remain in the electrolyte. Thus high-purity copper is obtained at the cathode.
6 Marks
Q28. A student says that the anode should be pure copper and cathode should be impure copper. Is this correct? Explain.
Q28. A student says that the anode should be pure copper and cathode should be impure copper. Is this correct? Explain.
Answer:
No, the statement is incorrect. In electrolytic refining of copper:
Anode = Impure copper
Cathode = Pure copper Copper from the impure anode dissolves into the electrolyte as Cu²⁺ ions. These ions are deposited as pure copper on the cathode. Therefore the arrangement must be reversed from the student's statement.
No, the statement is incorrect. In electrolytic refining of copper:
Anode = Impure copper
Cathode = Pure copper Copper from the impure anode dissolves into the electrolyte as Cu²⁺ ions. These ions are deposited as pure copper on the cathode. Therefore the arrangement must be reversed from the student's statement.
6 Marks
Q29. Why are gold and silver recovered from anode mud during copper refining?
Q29. Why are gold and silver recovered from anode mud during copper refining?
Answer:
Gold and silver are less reactive than copper. They do not readily oxidise and dissolve into the electrolyte during refining. Therefore they separate from the anode and settle at the bottom as anode mud. Since gold and silver are valuable metals, they can be recovered economically from the anode mud.
Gold and silver are less reactive than copper. They do not readily oxidise and dissolve into the electrolyte during refining. Therefore they separate from the anode and settle at the bottom as anode mud. Since gold and silver are valuable metals, they can be recovered economically from the anode mud.
6 Marks
Q30. Compare electrolytic refining at the anode and cathode.
Q30. Compare electrolytic refining at the anode and cathode.
| Feature | Anode | Cathode |
|---|---|---|
| Material | Impure copper | Pure copper |
| Terminal | Positive | Negative |
| Process | Oxidation | Reduction |
| Reaction | Cu → Cu²⁺ + 2e⁻ | Cu²⁺ + 2e⁻ → Cu |
| Mass | Decreases | Increases |
Conclusion: Copper is transferred from the impure anode to the pure cathode, producing highly pure copper.
10. Quick Revision / त्वरित पुनरावृत्ति
Electrolytic Refining = Purification of Metal by Electrolysis
Anode = Impure Copper = Positive
Cathode = Pure Copper = Negative
Electrolyte = Acidified CuSO₄
Anode: Cu → Cu²⁺ + 2e⁻
Cathode: Cu²⁺ + 2e⁻ → Cu
Ag + Au + other insoluble impurities → Anode Mud
⭐ CBSE Most Important:
Remember the sequence:
Impure Copper → Anode → Cu²⁺ → Electrolyte → Cathode → Pure Copper
Remember the sequence:
Impure Copper → Anode → Cu²⁺ → Electrolyte → Cathode → Pure Copper
