Extraction Based on Reactivity - Class 10 Science

⚙️ Extraction Based on Reactivity

क्रियाशीलता के आधार पर धातुओं का निष्कर्षण

Class 10 Science • CBSE • Foundation • Competitive Level

⚙️ Extraction Based on Reactivity / क्रियाशीलता के आधार पर निष्कर्षण

1. Basic Concept / मूल अवधारणा

English: The method used to extract a metal from its ore depends mainly on the reactivity of the metal. More reactive metals form more stable compounds and therefore require stronger methods of extraction.

हिन्दी: किसी धातु को उसके अयस्क से निकालने की विधि मुख्यतः उसकी क्रियाशीलता पर निर्भर करती है। अधिक क्रियाशील धातुएँ अधिक स्थायी यौगिक बनाती हैं, इसलिए इनके निष्कर्षण के लिए अधिक शक्तिशाली विधियों की आवश्यकता होती है।

2. Reactivity Series / क्रियाशीलता श्रेणी

K > Na > Ca > Mg > Al
↓
Highly Reactive Metals

Zn > Fe > Pb
↓
Moderately Reactive Metals

H > Cu > Hg > Ag > Au
↓
Low Reactivity / Less Reactive Metals

3. Classification Based on Reactivity / क्रियाशीलता के आधार पर वर्गीकरण

Group	Examples	General Extraction Method
Highly reactive	K, Na, Ca, Mg, Al	Electrolytic reduction
Moderately reactive	Zn, Fe, Pb	Roasting/Calcination followed by reduction
Low-reactivity	Cu, Hg, Ag, Au	Heating or chemical reduction; some may occur native

4. Highly Reactive Metals / अत्यधिक क्रियाशील धातुएँ

English: Highly reactive metals such as potassium, sodium, calcium, magnesium and aluminium have a strong tendency to combine with oxygen and other elements. Their compounds are difficult to reduce using ordinary reducing agents such as carbon.

हिन्दी: potassium, sodium, calcium, magnesium तथा aluminium जैसी अत्यधिक क्रियाशील धातुओं की ऑक्सीजन और अन्य तत्वों के साथ संयोजन की प्रवृत्ति बहुत अधिक होती है। इनके यौगिकों का carbon जैसे सामान्य अपचायक द्वारा अपचयन कठिन होता है।

Main method / मुख्य विधि: Electrolytic Reduction / वैद्युत अपघटनी अपचयन

5. Electrolytic Reduction / वैद्युत अपघटनी अपचयन

English: In electrolytic reduction, electricity is passed through the molten ionic compound. Metal ions gain electrons at the cathode and form the metal.

हिन्दी: वैद्युत अपघटनी अपचयन में पिघले हुए आयनिक यौगिक में विद्युत धारा प्रवाहित की जाती है। धातु आयन cathode पर इलेक्ट्रॉन ग्रहण करके धातु बनाते हैं।

Na⁺ + e⁻ → Na

Mg²⁺ + 2e⁻ → Mg

6. Extraction of Aluminium / Aluminium का निष्कर्षण

English: Aluminium is highly reactive and cannot generally be extracted by reducing aluminium oxide with carbon. It is obtained by electrolytic reduction of molten alumina.

हिन्दी: Aluminium अत्यधिक क्रियाशील है और aluminium oxide का carbon द्वारा सामान्यतः अपचयन नहीं किया जा सकता। इसे molten alumina के electrolytic reduction द्वारा प्राप्त किया जाता है।

Al³⁺ + 3e⁻ → Al

7. Moderately Reactive Metals / मध्यम क्रियाशील धातुएँ

English: Metals such as zinc, iron and lead are moderately reactive. Their ores are first concentrated and generally converted into oxides by roasting or calcination. The metal oxide is then reduced using a suitable reducing agent such as carbon or carbon monoxide.

हिन्दी: zinc, iron और lead जैसी धातुएँ मध्यम क्रियाशील होती हैं। इनके अयस्कों को पहले सांद्रित किया जाता है और roasting या calcination द्वारा ऑक्साइड में बदला जाता है। इसके बाद धातु ऑक्साइड का carbon या carbon monoxide जैसे अपचायक द्वारा अपचयन किया जाता है।

8. Example: Extraction of Zinc / उदाहरण: जिंक का निष्कर्षण

Step 1: Roasting of zinc sulphide

2ZnS + 3O₂ → 2ZnO + 2SO₂

Step 2: Reduction of zinc oxide

ZnO + C → Zn + CO

Thus zinc is obtained by reducing its oxide.

9. Example: Extraction of Iron / उदाहरण: आयरन का निष्कर्षण

English: Iron is extracted from iron ores in a blast furnace. Iron oxide is reduced mainly by carbon monoxide.

Fe₂O₃ + 3CO → 2Fe + 3CO₂

हिन्दी: आयरन का निष्कर्षण blast furnace में किया जाता है। Iron oxide का मुख्यतः carbon monoxide द्वारा अपचयन होता है।

10. Low-Reactivity Metals / कम क्रियाशील धातुएँ

English: Metals such as copper, mercury, silver and gold are relatively less reactive. Their compounds are comparatively less stable and therefore can often be reduced more easily.

हिन्दी: copper, mercury, silver और gold जैसी धातुएँ अपेक्षाकृत कम क्रियाशील होती हैं। इनके यौगिक अपेक्षाकृत कम स्थायी होते हैं, इसलिए इनका अपचयन आसानी से किया जा सकता है।

11. Example: Extraction of Mercury / उदाहरण: पारे का निष्कर्षण

Mercury is obtained from cinnabar (HgS). The sulphide ore is heated in air.

2HgS + 3O₂ → 2HgO + 2SO₂

The mercury(II) oxide is then decomposed by heating.

2HgO → 2Hg + O₂

12. Example: Extraction of Copper / उदाहरण: कॉपर का निष्कर्षण

English: Copper is less reactive than zinc and iron. Copper sulphide ores undergo roasting and subsequent reduction/conversion steps to obtain copper.

हिन्दी: कॉपर, zinc और iron से कम क्रियाशील है। Copper sulphide ores को roasting तथा आगे की उपयुक्त प्रक्रियाओं द्वारा कॉपर में बदला जाता है।

13. Metals Found in Native State / मुक्त अवस्था में पाए जाने वाली धातुएँ

English: Very low-reactivity metals such as gold and platinum may occur in the Earth's crust in the free or native state.

हिन्दी: बहुत कम क्रियाशील धातुएँ जैसे gold और platinum पृथ्वी की पर्पटी में मुक्त या native state में पाई जा सकती हैं।

Low reactivity → less tendency to form compounds → possibility of occurrence in free state.

14. Why Carbon Cannot Reduce Highly Reactive Metals? / Carbon अत्यधिक क्रियाशील धातुओं का अपचयन क्यों नहीं कर सकता?

English: Highly reactive metals have a greater affinity for oxygen than carbon. Their oxides are therefore very stable and cannot generally be reduced by carbon.

हिन्दी: अत्यधिक क्रियाशील धातुओं की oxygen के प्रति affinity carbon से अधिक होती है। इसलिए इनके oxides बहुत स्थायी होते हैं और carbon द्वारा सामान्यतः उनका अपचयन नहीं किया जा सकता।

15. Quick Revision / त्वरित पुनरावृत्ति

Metal Group	Examples	Extraction Method
Highly Reactive	K, Na, Ca, Mg, Al	Electrolysis
Moderately Reactive	Zn, Fe, Pb	Roasting/Calcination → Reduction
Low Reactive	Cu, Hg, Ag	Heating / Chemical Reduction
Very Low Reactive	Au, Pt	May occur in native state

16. 30 MCQs / 30 बहुविकल्पीय प्रश्न

17. 30 Subjective Questions with Answers / 30 वर्णनात्मक प्रश्न

Class 10 Science – Electrolytic Refining

Class 10 Science – Chapter 3

Electrolytic Refining

वैद्युत अपघटनी परिष्करण | Electrolytic Refining of Metals

×

1. What is Electrolytic Refining? | वैद्युत अपघटनी परिष्करण क्या है?

English:
Electrolytic refining is a process used to obtain highly pure metals by using electrolysis.

हिंदी:
वैद्युत अपघटनी परिष्करण वह प्रक्रिया है जिसमें विद्युत अपघटन की सहायता से अशुद्ध धातु को अत्यधिक शुद्ध धातु में परिवर्तित किया जाता है।

Purpose of Electrolytic Refining

The main purpose is to remove impurities from an impure metal and obtain pure metal.

इस प्रक्रिया का मुख्य उद्देश्य अशुद्ध धातु से अशुद्धियों को हटाकर शुद्ध धातु प्राप्त करना है।

Metals commonly refined electrolytically:
Copper, Zinc, Nickel, Silver, Gold and some other metals.

Basic Principle

Electric Current → Electrolysis → Transfer of Metal Ions → Pure Metal

The impure metal is generally made the anode, while a thin sheet of pure metal is used as the cathode.

अशुद्ध धातु को सामान्यतः ऐनोड तथा शुद्ध धातु की पतली पट्टी को कैथोड बनाया जाता है।

Exam Point:
Electrolytic refining is based on the principle of electrolysis.

×

2. Electrolytic Refining of Copper | ताँबे का वैद्युत अपघटनी परिष्करण

English:
Electrolytic refining of copper is carried out to obtain very pure copper from impure copper.

हिंदी:
अशुद्ध ताँबे से अत्यधिक शुद्ध ताँबा प्राप्त करने के लिए वैद्युत अपघटनी परिष्करण किया जाता है।

Arrangement

Anode: Impure copper slab

Cathode: Thin sheet of pure copper

Electrolyte: Acidified copper sulphate solution (CuSO₄)

Power Supply: Direct current (DC)

Simple Representation

Impure Cu (Anode) | CuSO₄ Solution | Pure Cu (Cathode)

What happens at the Anode?

When electric current is passed, copper atoms from the impure copper anode lose electrons and enter the solution as Cu²⁺ ions.

Cu → Cu²⁺ + 2e⁻

Thus, the impure copper anode gradually dissolves.

What happens at the Cathode?

Cu²⁺ ions present in the electrolyte gain electrons at the cathode and are deposited as pure copper.

Cu²⁺ + 2e⁻ → Cu

Therefore, the cathode becomes thicker due to deposition of pure copper.

Overall Effect

Impure copper anode decreases in size, while pure copper cathode increases in size.

×

3. Role of Anode, Cathode & Electrolyte

1. Anode | ऐनोड

English:
The impure metal is connected to the positive terminal and acts as the anode.

हिंदी:
अशुद्ध धातु को बैटरी के धनात्मक टर्मिनल से जोड़ा जाता है और यह ऐनोड का कार्य करती है।

At the anode, metal atoms lose electrons and form positive metal ions.

M → Mⁿ⁺ + ne⁻

2. Cathode | कैथोड

English:
A thin sheet of pure metal is connected to the negative terminal and acts as the cathode.

हिंदी:
शुद्ध धातु की पतली पट्टी को ऋणात्मक टर्मिनल से जोड़ा जाता है और यह कैथोड का कार्य करती है।

Metal ions gain electrons and deposit as pure metal on the cathode.

Mⁿ⁺ + ne⁻ → M

3. Electrolyte | इलेक्ट्रोलाइट

English:
The electrolyte is a solution containing ions of the metal being refined.

हिंदी:
इलेक्ट्रोलाइट वह विलयन है जिसमें उस धातु के आयन उपस्थित होते हैं जिसका परिष्करण किया जा रहा है।

For copper refining, acidified copper sulphate solution is used.

CuSO₄(aq) → Cu²⁺(aq) + SO₄²⁻(aq)

Remember:
Anode = Impure Metal
Cathode = Pure Metal Sheet
Electrolyte = Metal Salt Solution

×

4. Reactions & Working | अभिक्रियाएँ एवं कार्यविधि

Step 1 – Connection

The impure copper slab is connected to the positive terminal of the battery.

अशुद्ध ताँबे की पट्टी को बैटरी के धनात्मक टर्मिनल से जोड़ा जाता है।

Step 2 – Cathode Connection

A thin sheet of pure copper is connected to the negative terminal.

शुद्ध ताँबे की पतली पट्टी को बैटरी के ऋणात्मक टर्मिनल से जोड़ा जाता है।

Step 3 – Electrolyte

Both electrodes are dipped in acidified CuSO₄ solution.

CuSO₄(aq) → Cu²⁺ + SO₄²⁻

Step 4 – Oxidation at Anode

Cu → Cu²⁺ + 2e⁻

Copper atoms from the impure anode enter the solution as Cu²⁺ ions.

Step 5 – Reduction at Cathode

Cu²⁺ + 2e⁻ → Cu

Copper ions are reduced and deposited as pure copper on the cathode.

Step 6 – Impurities

Some impurities dissolve into the electrolyte, while insoluble impurities settle at the bottom of the electrolytic cell.

Impurities → Anode Mud / Solution

Redox Concept:
Oxidation occurs at the anode and reduction occurs at the cathode.

×

5. Anode Mud & Pure Copper | ऐनोड मड एवं शुद्ध ताँबा

Anode Mud

English:
The insoluble impurities present in impure copper settle at the bottom of the electrolytic tank as anode mud.

हिंदी:
अशुद्ध ताँबे में उपस्थित अघुलनशील अशुद्धियाँ विद्युत अपघटनी टैंक के नीचे बैठकर ऐनोड मड बनाती हैं।

Important Valuable Metals

Anode mud may contain valuable metals such as silver and gold.

Important:
Silver and gold can be recovered from the anode mud as valuable by-products.

What happens to the electrodes?

Impure Anode: Gradually dissolves and becomes thinner.

Pure Cathode: Pure copper gets deposited and the sheet becomes thicker.

Overall Copper Refining

Impure Copper → Electrolysis → Pure Copper

Competitive Concept

Question: Why does the concentration of Cu²⁺ ions remain approximately unchanged during copper refining?

Answer: Cu²⁺ ions are produced at the anode as copper dissolves and are simultaneously consumed at the cathode when pure copper is deposited.

Key Formula:
At anode: Cu → Cu²⁺ + 2e⁻
At cathode: Cu²⁺ + 2e⁻ → Cu

×

30 MCQs – Electrolytic Refining

1. What is the main purpose of electrolytic refining?

A. To increase impurity

B. To obtain pure metal

C. To convert metal into gas

D. To make an alloy

Answer: B. To obtain pure metal

Electrolytic refining removes impurities from metals.

2. Electrolytic refining is based on:

A. Combustion

B. Electrolysis

C. Sublimation

D. Distillation

Answer: B. Electrolysis

3. In copper refining, the anode is:

A. Pure copper

B. Impure copper

C. Zinc

D. Iron

Answer: B. Impure copper

4. In copper refining, the cathode is:

A. Impure copper slab

B. Pure copper sheet

C. Zinc sheet

D. Iron rod

Answer: B. Pure copper sheet

5. The electrolyte used in copper refining is:

A. NaCl solution

B. Acidified CuSO₄ solution

C. HCl only

D. NaOH solution

Answer: B. Acidified CuSO₄ solution

6. The impure copper anode is connected to:

A. Negative terminal

B. Positive terminal

C. Both terminals

D. No terminal

Answer: B. Positive terminal

7. The pure copper cathode is connected to:

A. Positive terminal

B. Negative terminal

C. Both terminals

D. Earth only

Answer: B. Negative terminal

8. Oxidation occurs at:

A. Cathode

B. Anode

C. Electrolyte only

D. Battery

Answer: B. Anode

9. Reduction occurs at:

A. Anode

B. Cathode

C. Electrolyte

D. Salt bridge

Answer: B. Cathode

10. Which reaction occurs at the copper anode?

A. Cu²⁺ + 2e⁻ → Cu

B. Cu → Cu²⁺ + 2e⁻

C. Cu + 2e⁻ → Cu²⁺

D. Cu²⁺ → Cu + 2e⁻

Answer: B. Cu → Cu²⁺ + 2e⁻

11. Which reaction occurs at the cathode?

A. Cu → Cu²⁺ + 2e⁻

B. Cu²⁺ + 2e⁻ → Cu

C. Cu → Cu⁺

D. Cu²⁺ → Cu³⁺

Answer: B. Cu²⁺ + 2e⁻ → Cu

12. What is deposited on the cathode?

A. Impure copper

B. Pure copper

C. Sulphur

D. Zinc

Answer: B. Pure copper

13. The impure copper anode:

A. Becomes thicker

B. Gradually dissolves

C. Does not change

D. Converts into gas

Answer: B. Gradually dissolves

14. The pure copper cathode:

A. Becomes thinner

B. Becomes thicker

C. Disappears

D. Produces gas

Answer: B. Becomes thicker

15. Insoluble impurities settle as:

A. Cathode deposit

B. Anode mud

C. Electrolyte

D. Copper sulphate

Answer: B. Anode mud

16. Anode mud may contain:

A. Gold and silver

B. Sodium only

C. Chlorine only

D. Water only

Answer: A. Gold and silver

17. The metal ions moving towards cathode during copper refining are:

A. Cu²⁺

B. SO₄²⁻

C. Cl⁻

D. OH⁻

Answer: A. Cu²⁺

18. In electrolytic refining, metal ions gain electrons at the:

A. Anode

B. Cathode

C. Electrolyte

D. Battery

Answer: B. Cathode

19. The process at cathode is:

A. Oxidation

B. Reduction

C. Neutralisation

D. Combustion

Answer: B. Reduction

20. The process at anode is:

A. Reduction

B. Oxidation

C. Neutralisation

D. Precipitation only

Answer: B. Oxidation

21. Which current is generally used in electrolytic refining?

A. Direct current

B. Alternating current only

C. No current

D. Static electricity

Answer: A. Direct current

22. What happens to Cu²⁺ ions at the cathode?

A. They lose electrons

B. They gain electrons

C. They become SO₄²⁻

D. They evaporate

Answer: B. They gain electrons

23. Which equation represents reduction of copper ions?

A. Cu → Cu²⁺ + 2e⁻

B. Cu²⁺ + 2e⁻ → Cu

C. Cu + SO₄ → CuSO₄

D. Cu²⁺ → Cu³⁺

Answer: B

24. Which equation represents oxidation of copper?

A. Cu²⁺ + 2e⁻ → Cu

B. Cu → Cu²⁺ + 2e⁻

C. CuSO₄ → Cu

D. Cu + 2e⁻ → Cu²⁺

Answer: B

25. Which statement is correct?

A. Anode is pure copper

B. Cathode is impure copper

C. Anode is impure copper and cathode is pure copper

D. Both are impure copper

Answer: C

26. The electrolyte provides:

A. Metal ions

B. Only electrons

C. Only gases

D. No ions

Answer: A. Metal ions

27. Which is a valuable by-product obtained from anode mud?

A. Gold

B. Sodium chloride

C. Water

D. Oxygen only

Answer: A. Gold

28. Electrolytic refining is an example of:

A. Electrochemical process

B. Mechanical separation only

C. Physical filtration only

D. Sublimation

Answer: A. Electrochemical process

29. During copper refining, pure copper is deposited on:

A. Anode

B. Cathode

C. Electrolyte surface

D. Bottom only

Answer: B. Cathode

30. Which sequence is correct for copper refining?

A. Pure Cu → Anode → Electrolyte → Impure Cu

B. Impure Cu → Anode → Cu²⁺ → Cathode → Pure Cu

C. Pure Cu → Electrolyte → Anode Mud

D. Cu²⁺ → Anode → Impure Cu

Answer: B

×

30 Subjective Questions – Complete Solutions

1 Mark Questions

Q1. What is electrolytic refining?

Electrolytic refining is the process of obtaining pure metal from an impure metal by electrolysis.

Q2. Which metal is commonly refined electrolytically?

Copper is commonly refined by electrolytic refining.

Q3. What is used as the anode in copper refining?

An impure copper slab is used as the anode.

Q4. What is used as the cathode?

A thin sheet of pure copper is used as the cathode.

Q5. Name the electrolyte used in copper refining.

Acidified copper sulphate (CuSO₄) solution is used.

2 Mark Questions

Q6. Define electrolytic refining.

Electrolytic refining is a method of purifying an impure metal by passing electric current through a suitable electrolyte.

Q7. What is the role of anode in copper refining?

The impure copper slab acts as the anode. Copper atoms lose electrons and enter the electrolyte as Cu²⁺ ions.

Cu → Cu²⁺ + 2e⁻

Q8. What is the role of cathode?

A thin pure copper sheet acts as the cathode. Cu²⁺ ions gain electrons and deposit as pure copper.

Cu²⁺ + 2e⁻ → Cu

Q9. What is the role of electrolyte?

The electrolyte provides mobile ions required for the conduction of electricity and transport of metal ions.

Q10. What is anode mud?

Insoluble impurities that settle at the bottom of the electrolytic cell during copper refining are called anode mud.

3 Mark Questions

Q11. Explain electrolytic refining of copper.

In copper refining, impure copper is used as anode and pure copper sheet as cathode. Acidified CuSO₄ solution is used as electrolyte.

At anode:
Cu → Cu²⁺ + 2e⁻

At cathode:
Cu²⁺ + 2e⁻ → Cu

Thus pure copper is deposited on the cathode.

Q12. Write the functions of anode, cathode and electrolyte.

Anode: Supplies metal ions by oxidation.
Cathode: Receives metal ions and deposits pure metal by reduction.
Electrolyte: Provides ions and conducts electric current.

Q13. What happens to copper at the anode and cathode?

At the anode, copper is oxidised:
Cu → Cu²⁺ + 2e⁻

At the cathode, Cu²⁺ is reduced:
Cu²⁺ + 2e⁻ → Cu

Q14. Why does the cathode become thicker during copper refining?

Cu²⁺ ions from the electrolyte gain electrons at the cathode and are deposited as pure copper. Therefore, the cathode gradually becomes thicker.

Q15. Why does the anode become thinner?

Copper atoms from the impure anode lose electrons and enter the solution as Cu²⁺ ions. Therefore, the anode gradually dissolves and becomes thinner.

4 Mark Questions

Q16. Explain the complete setup of electrolytic refining of copper.

The setup consists of:

1. Impure copper slab as anode.
2. Thin pure copper sheet as cathode.
3. Acidified CuSO₄ solution as electrolyte.
4. Direct current supply.

When current passes, copper dissolves from the anode and deposits as pure copper on the cathode.

Q17. Explain oxidation and reduction during copper refining.

Oxidation at anode:
Cu → Cu²⁺ + 2e⁻

Copper loses electrons.

Reduction at cathode:
Cu²⁺ + 2e⁻ → Cu

Copper ions gain electrons.

Thus, the process involves both oxidation and reduction.

Q18. Explain the formation of anode mud.

Impure copper contains insoluble impurities such as some precious metals. During electrolysis, copper dissolves from the anode, while insoluble impurities do not dissolve and settle at the bottom of the tank.

These deposited impurities are called anode mud.

Q19. Why is acidified CuSO₄ solution used as electrolyte?

CuSO₄ provides Cu²⁺ ions required for deposition of copper at the cathode. Acidification improves the conductivity of the solution and helps maintain suitable conditions for electrolysis.

Q20. Write the electrode reactions in electrolytic refining of copper.

Anode:
Cu → Cu²⁺ + 2e⁻

Cathode:
Cu²⁺ + 2e⁻ → Cu

These reactions represent oxidation and reduction respectively.

5 Mark Questions

Q21. Describe electrolytic refining of copper in detail.

Electrolytic refining is used to obtain pure copper from impure copper.

An impure copper slab is connected to the positive terminal and acts as the anode. A thin sheet of pure copper is connected to the negative terminal and acts as the cathode.

Acidified CuSO₄ solution is used as electrolyte.

At the anode:
Cu → Cu²⁺ + 2e⁻

At the cathode:
Cu²⁺ + 2e⁻ → Cu

Pure copper gets deposited on the cathode, while insoluble impurities settle as anode mud.

Q22. Explain the role of all three components used in electrolytic refining.

1. Anode: Impure metal is used as anode. It undergoes oxidation and supplies metal ions.

2. Cathode: Pure metal sheet is used as cathode. Metal ions gain electrons and deposit on it.

3. Electrolyte: It contains ions of the metal being refined and provides a conducting medium.

For copper, these are impure Cu, pure Cu and acidified CuSO₄ solution respectively.

Q23. Explain what happens when electric current is passed through the copper refining cell.

When current is passed:

1. Copper atoms at the anode lose electrons.
2. Cu²⁺ ions enter the electrolyte.
3. Cu²⁺ ions move towards the cathode.
4. At the cathode they gain electrons.
5. Pure copper is deposited on the cathode.
6. Insoluble impurities collect as anode mud.

Q24. What happens to impurities during electrolytic refining?

Different impurities behave differently.

Some impurities may dissolve into the electrolyte, while insoluble impurities settle at the bottom as anode mud.

Valuable metals such as gold and silver may be recovered from the anode mud.

Q25. Why is electrolytic refining important in metallurgy?

Electrolytic refining is important because it produces highly pure metals required for electrical, electronic and industrial applications.

For example, highly pure copper is required for electrical wires because impurities can affect electrical conductivity.

6 Mark Questions

Q26. Explain electrolytic refining of copper with a labelled arrangement and reactions.

Arrangement:

Impure Copper → Anode (+)
Pure Copper Sheet → Cathode (−)
Acidified CuSO₄ → Electrolyte

At Anode – Oxidation:
Cu → Cu²⁺ + 2e⁻

Copper atoms from the impure anode enter the solution.

At Cathode – Reduction:
Cu²⁺ + 2e⁻ → Cu

Pure copper is deposited on the cathode.

Impurities:
Insoluble impurities settle as anode mud, while some soluble impurities remain in the electrolyte.

Thus, impure copper is converted into highly pure copper.

Q27. Explain the complete mechanism of copper purification by electrolysis.

The impure copper slab is connected to the positive terminal of the DC source and acts as anode.

A thin sheet of pure copper is connected to the negative terminal and acts as cathode.

Both electrodes are immersed in acidified CuSO₄ solution.

When current flows, copper atoms at the anode lose electrons and become Cu²⁺ ions.

Cu²⁺ ions move through the electrolyte and are reduced at the cathode.

Cu²⁺ + 2e⁻ → Cu

Pure copper deposits on the cathode.

The impure anode gradually becomes smaller and the pure cathode becomes thicker.

Insoluble impurities form anode mud.

Q28. Differentiate between anode and cathode in electrolytic refining.

Anode:
1. It is connected to positive terminal.
2. It is generally made of impure metal.
3. Oxidation occurs here.
4. Metal atoms lose electrons.
5. Anode gradually dissolves.

Cathode:
1. It is connected to negative terminal.
2. It is generally a thin sheet of pure metal.
3. Reduction occurs here.
4. Metal ions gain electrons.
5. Pure metal is deposited on it.

Q29. Explain anode mud and its importance.

Anode mud is the insoluble material that settles at the bottom of the electrolytic refining tank.

During copper refining, copper dissolves from the anode, but certain insoluble impurities do not enter the solution.

These impurities settle at the bottom.

Anode mud can contain valuable metals such as silver and gold.

Therefore, anode mud is economically important because valuable metals can be recovered from it.

Q30. “Electrolytic refining is both an oxidation and reduction process.” Explain.

Electrolytic refining involves oxidation at the anode and reduction at the cathode.

At anode:
Copper atoms lose electrons:
Cu → Cu²⁺ + 2e⁻

This is oxidation.

At cathode:
Copper ions gain electrons:
Cu²⁺ + 2e⁻ → Cu

This is reduction.

Therefore, electrolytic refining is a redox process in which oxidation and reduction occur simultaneously at different electrodes.

Class 10 Science | Electrolytic Refining
Definition + Copper Refining + Anode + Cathode + Electrolyte + Reactions + Anode Mud + 30 MCQs + 30 Subjective Questions

⛏️ Extraction of Metals

धातुओं का निष्कर्षण | Class 10 Science

CBSE • Foundation • Competitive Level

⛏️ Extraction of Metals / धातुओं का निष्कर्षण

1. What is Extraction of Metals? / धातुओं का निष्कर्षण क्या है?

English: The process of obtaining a pure metal from its naturally occurring source, usually an ore, is called extraction of metals.

हिन्दी: प्राकृतिक स्रोत, विशेषकर अयस्क, से शुद्ध धातु प्राप्त करने की प्रक्रिया को धातुओं का निष्कर्षण कहते हैं।

2. What is an Ore? / अयस्क क्या है?

English: An ore is a mineral from which a metal can be extracted conveniently and economically.

हिन्दी: अयस्क वह खनिज है जिससे धातु को सुविधापूर्वक और आर्थिक रूप से निकाला जा सकता है।

All ores are minerals, but all minerals are not ores.
सभी अयस्क खनिज होते हैं, लेकिन सभी खनिज अयस्क नहीं होते।

3. Main Steps in Extraction of Metals / धातु निष्कर्षण के मुख्य चरण

Concentration of Ore
↓
Conversion of Concentrated Ore into Oxide
↓
Reduction of Metal Oxide
↓
Refining of Metal

Step 1 — Concentration:
Removal of unwanted impurities or gangue from the ore.
अयस्क से मिट्टी, रेत आदि अशुद्धियों को हटाना।

Step 2 — Conversion into Oxide:
The concentrated ore is converted into its oxide by roasting or calcination.
सांद्रित अयस्क को roasting या calcination द्वारा ऑक्साइड में बदला जाता है।

Step 3 — Reduction:
Metal oxide is reduced to obtain the metal.
धातु ऑक्साइड का अपचयन करके धातु प्राप्त की जाती है।

Step 4 — Refining:
Impure metal is purified.
अशुद्ध धातु को शुद्ध किया जाता है।

4. What is Concentration of Ore? / अयस्क का सांद्रण क्या है?

English: Concentration of ore is the process of removing unwanted materials such as soil, sand and rocky impurities from the ore.

हिन्दी: अयस्क से मिट्टी, रेत, पत्थर तथा अन्य अवांछित अशुद्धियों को हटाने की प्रक्रिया को अयस्क का सांद्रण कहते हैं।

Ore + Gangue → Concentrated Ore

5. What is Gangue? / गैंग क्या है?

English: The unwanted earthy or rocky impurities present in an ore are called gangue.

हिन्दी: अयस्क में उपस्थित अवांछित मिट्टी, रेत तथा चट्टानी अशुद्धियों को गैंग कहते हैं।

6. Why is Ore Converted into Oxide? / अयस्क को ऑक्साइड में क्यों बदला जाता है?

English: Metal oxides can generally be reduced more easily to obtain metals than many sulphides or carbonates. Therefore, sulphide and carbonate ores are often converted into oxides before reduction.

हिन्दी: अनेक सल्फाइड और कार्बोनेट अयस्कों की तुलना में धातु ऑक्साइड का अपचयन करके धातु प्राप्त करना अधिक आसान होता है। इसलिए सल्फाइड और कार्बोनेट अयस्कों को प्रायः पहले ऑक्साइड में बदला जाता है।

7. Why is Roasting carried out? / Roasting क्यों की जाती है?

English: Roasting is the process of heating a sulphide ore strongly in the presence of excess air or oxygen. It converts the sulphide ore into metal oxide and releases sulphur dioxide gas.

हिन्दी: सल्फाइड अयस्क को अधिक वायु या ऑक्सीजन की उपस्थिति में तेज गर्म करने की प्रक्रिया को roasting कहते हैं। इससे सल्फाइड अयस्क धातु ऑक्साइड में बदल जाता है और SO₂ गैस निकलती है।

2ZnS + 3O₂ → 2ZnO + 2SO₂

2PbS + 3O₂ → 2PbO + 2SO₂

Remember:
Roasting → Sulphide ore + Excess air/oxygen + Heat → Oxide + SO₂

याद रखें: Roasting मुख्यतः सल्फाइड अयस्कों के लिए प्रयोग की जाती है।

8. What is Calcination? / Calcination क्या है?

English: Calcination is the process of heating carbonate ores strongly in limited or no air. It converts carbonate ores into metal oxides and releases carbon dioxide.

हिन्दी: कार्बोनेट अयस्क को सीमित या बिना वायु के तेज गर्म करने की प्रक्रिया को calcination कहते हैं। इससे धातु ऑक्साइड और CO₂ बनते हैं।

ZnCO₃ → ZnO + CO₂

CaCO₃ → CaO + CO₂

9. Roasting vs Calcination / Roasting और Calcination में अंतर

Roasting	Calcination
Usually used for sulphide ores	Usually used for carbonate ores
Excess air/oxygen is used	Limited or no air is used
SO₂ may be released	CO₂ is generally released
Example: 2ZnS + 3O₂ → 2ZnO + 2SO₂	Example: ZnCO₃ → ZnO + CO₂

10. Reduction of Metal Oxide / धातु ऑक्साइड का अपचयन

English: In reduction, oxygen is removed from the metal oxide to obtain the metal.

हिन्दी: अपचयन में धातु ऑक्साइड से ऑक्सीजन हटाकर धातु प्राप्त की जाती है।

ZnO + C → Zn + CO

Fe₂O₃ + 3CO → 2Fe + 3CO₂

11. Reduction with Carbon / कार्बन द्वारा अपचयन

English: Metals which are moderately reactive can often be obtained by reducing their oxides using carbon.

हिन्दी: मध्यम क्रियाशील धातुओं को उनके ऑक्साइड का कार्बन द्वारा अपचयन करके प्राप्त किया जा सकता है।

ZnO + C → Zn + CO

2CuO + C → 2Cu + CO₂

12. Electrolytic Reduction / वैद्युत अपघटनी अपचयन

English: Highly reactive metals such as sodium, potassium, calcium, magnesium and aluminium cannot generally be obtained by reduction with carbon. Their compounds are electrolysed to obtain the metal.

हिन्दी: अत्यधिक क्रियाशील धातुओं जैसे sodium, potassium, calcium, magnesium और aluminium को सामान्यतः carbon द्वारा प्राप्त नहीं किया जा सकता। इनके यौगिकों का विद्युत अपघटन करके धातु प्राप्त की जाती है।

Na⁺ + e⁻ → Na

13. Thermite Reaction / थर्माइट अभिक्रिया

English: Aluminium is a strong reducing agent. It can reduce certain metal oxides to metals and releases a large amount of heat.

हिन्दी: Aluminium एक शक्तिशाली अपचायक है। यह कुछ धातु ऑक्साइडों का अपचयन करके धातु प्राप्त करता है और बहुत अधिक ऊष्मा उत्पन्न करता है।

Fe₂O₃ + 2Al → 2Fe + Al₂O₃ + Heat

This reaction is called the Thermite reaction.

14. Extraction According to Reactivity / क्रियाशीलता के आधार पर निष्कर्षण

Reactivity	Examples	General Method
Highly reactive	K, Na, Ca, Mg, Al	Electrolytic reduction
Moderately reactive	Zn, Fe, Pb	Reduction of oxides using carbon/CO
Low reactive	Cu, Hg, Ag	Heating or suitable chemical reduction
Very low reactive	Au, Pt	Often found in native/free state

15. Refining of Metals / धातुओं का परिष्करण

English: The process of removing impurities from an extracted metal to obtain a high-purity metal is called refining.

हिन्दी: निष्कर्षित धातु से अशुद्धियाँ हटाकर उच्च शुद्धता वाली धातु प्राप्त करने की प्रक्रिया को धातु का परिष्करण कहते हैं।

Example: Electrolytic refining is commonly used for copper.

16. Electrolytic Refining of Copper / कॉपर का वैद्युत अपघटनी परिष्करण

English: In electrolytic refining of copper:

• Impure copper → Anode
• Pure copper → Cathode
• Acidified CuSO₄ → Electrolyte

During electrolysis, pure copper gets deposited at the cathode.

हिन्दी: कॉपर के वैद्युत अपघटनी परिष्करण में अशुद्ध कॉपर anode, शुद्ध कॉपर cathode तथा अम्लीकृत CuSO₄ electrolyte होता है। विद्युत अपघटन के दौरान शुद्ध कॉपर cathode पर जमा होता है।

17. 30 MCQs / 30 बहुविकल्पीय प्रश्न

18. 30 Subjective Questions with Answers / 30 वर्णनात्मक प्रश्न