Class 10 Science – Electrolytic Refining

Class 10 Science – Chapter 3

Electrolytic Refining

वैद्युत अपघटनी परिष्करण | Electrolytic Refining of Metals

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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.

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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.

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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

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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.

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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

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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

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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

Class 10 Science – Occurrence of Metals

Class 10 Science – Chapter 3

Occurrence of Metals

धातुओं की प्राकृतिक अवस्था में उपस्थिति | Minerals, Ores & Differences

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1. What are Minerals? | खनिज क्या हैं?

English:
Minerals are naturally occurring elements or compounds found in the Earth's crust.

हिंदी:
खनिज वे प्राकृतिक रूप से पाए जाने वाले तत्व या यौगिक हैं जो पृथ्वी की भूपर्पटी में पाए जाते हैं।

Examples of Minerals

Many metals occur in nature in the form of minerals. These minerals may contain the desired metal along with other substances.

कई धातुएँ प्रकृति में खनिजों के रूप में पाई जाती हैं। इन खनिजों में वांछित धातु के साथ अन्य पदार्थ भी उपस्थित हो सकते हैं।

Examples:
Bauxite – source of aluminium
Haematite – source of iron
Zinc blende – source of zinc
Copper pyrites – source of copper

Important Point

Every ore is a mineral, but every mineral is not an ore.

याद रखें:
प्रत्येक अयस्क एक खनिज होता है, लेकिन प्रत्येक खनिज अयस्क नहीं होता।

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2. What is an Ore? | अयस्क क्या है?

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

हिंदी:
अयस्क वह खनिज है जिससे धातु को सुविधापूर्वक तथा आर्थिक रूप से लाभदायक तरीके से निकाला जा सकता है।

Meaning of Economically

The extraction process should not cost more than the value of the metal obtained.

धातु के निष्कर्षण की लागत, प्राप्त धातु के आर्थिक मूल्य की तुलना में उचित होनी चाहिए।

Important Examples

Iron: Haematite (Fe₂O₃)

Aluminium: Bauxite

Zinc: Zinc blende (ZnS)

Copper: Copper pyrites (CuFeS₂)

Why is an ore useful?

An ore contains sufficient amount of the metal or its compound and allows extraction by practical methods.

Exam Definition:
“An ore is a mineral from which a metal can be extracted profitably or economically.”

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3. Difference Between Minerals and Ores

Minerals / खनिज

Naturally occurring substances containing metals or their compounds.

प्राकृतिक रूप से पाए जाने वाले पदार्थ जिनमें धातु या उसके यौगिक हो सकते हैं।

Ores / अयस्क

Minerals from which metals can be extracted conveniently and economically.

ऐसे खनिज जिनसे धातु को सुविधापूर्वक एवं आर्थिक रूप से निकाला जा सकता है।

Key Differences

1. Meaning
Mineral is a naturally occurring substance containing a metal or its compound.
Ore is a mineral suitable for economical extraction of metal.

2. Economic Value
A mineral may or may not be economically useful.
An ore is economically useful for extraction.

3. Metal Content
A mineral may contain a low concentration of the desired metal.
An ore generally contains sufficient concentration for practical extraction.

4. Relationship
All ores are minerals, but all minerals are not ores.

Best One-Line Answer:
All ores are minerals, but all minerals are not ores because only those minerals from which metals can be extracted economically are called ores.

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4. Occurrence of Metals | धातुओं की प्राकृतिक उपस्थिति

Metals occur in the Earth's crust either in free state or in combined state.

धातुएँ पृथ्वी की भूपर्पटी में या तो स्वतंत्र अवस्था में या संयुक्त अवस्था में पाई जाती हैं।

1. Free State / स्वतंत्र अवस्था

Less reactive metals are sometimes found in the free state because they do not readily react with other substances.

Examples: Gold, silver and platinum may occur in native/free form.

2. Combined State / संयुक्त अवस्था

Highly reactive metals are generally found in combined form as compounds such as oxides, sulphides, carbonates and halides.

Examples:
Iron – oxides such as haematite
Zinc – sulphide such as zinc blende
Copper – sulphide minerals such as copper pyrites

Relation with Reactivity

More Reactive Metal → Usually Combined State

Less Reactive Metal → May Occur in Free State

Important:
The occurrence of a metal in nature depends greatly on its reactivity and its tendency to form stable compounds.

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5. Examples & Important Concepts

Important Ores

Aluminium: Bauxite
Iron: Haematite
Zinc: Zinc blende
Copper: Copper pyrites
Mercury: Cinnabar

Mineral vs Ore – Quick Concept

Suppose a rock contains a metal compound, but the amount of metal is very small and extraction is expensive. It may be a mineral but is not considered a useful ore.

यदि किसी खनिज में धातु की मात्रा बहुत कम हो और उससे धातु निकालना महँगा हो, तो वह खनिज अयस्क के रूप में उपयोगी नहीं माना जाता।

Ore → Metal Extraction

Ore → Concentration → Extraction → Refining → Metal

The exact extraction steps depend on the reactivity and nature of the metal and its ore.

Competitive Concept

Question: Why are highly reactive metals rarely found in free state?

Answer: Highly reactive metals readily react with oxygen, water, sulphur and other substances, so they generally occur as stable compounds.

Question: Why can gold occur in free state?

Answer: Gold is very unreactive and therefore has a low tendency to combine with other elements.

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30 MCQs – Occurrence of Metals

1. What are minerals?

A. Only artificially prepared substances

B. Naturally occurring elements or compounds

C. Only metals

D. Only gases

Answer: B. Naturally occurring elements or compounds

Minerals occur naturally in the Earth's crust.

2. What is an ore?

A. Any rock

B. A mineral from which metal can be extracted economically

C. Pure metal only

D. A non-metal

Answer: B

3. Which statement is correct?

A. Every mineral is an ore

B. Every ore is a mineral

C. No ore is a mineral

D. Minerals and ores are identical

Answer: B. Every ore is a mineral

4. Which statement is true?

A. All minerals are ores

B. All ores are minerals but all minerals are not ores

C. No mineral is an ore

D. Ores contain no metals

Answer: B

5. Bauxite is an important ore of:

A. Iron

B. Aluminium

C. Copper

D. Zinc

Answer: B. Aluminium

6. Haematite is an important ore of:

A. Iron

B. Zinc

C. Aluminium

D. Copper

Answer: A. Iron

7. Zinc blende is an ore of:

A. Zinc

B. Iron

C. Aluminium

D. Sodium

Answer: A. Zinc

8. Copper pyrites is associated with:

A. Copper

B. Aluminium

C. Sodium

D. Calcium

Answer: A. Copper

9. Which metal may occur in free state?

A. Sodium

B. Potassium

C. Gold

D. Calcium

Answer: C. Gold

10. Highly reactive metals generally occur in:

A. Free state

B. Combined state

C. Gaseous state only

D. Liquid state only

Answer: B. Combined state

11. The occurrence of metals depends greatly on:

A. Colour only

B. Reactivity

C. Shape only

D. Density only

Answer: B. Reactivity

12. Which is a less reactive metal?

A. Sodium

B. Potassium

C. Gold

D. Calcium

Answer: C. Gold

13. An ore should allow extraction of metal:

A. At any cost

B. Economically

C. Only manually

D. Never

Answer: B. Economically

14. Which of the following is NOT generally an ore?

A. Bauxite

B. Haematite

C. Zinc blende

D. Pure water

Answer: D. Pure water

15. Cinnabar is associated with:

A. Mercury

B. Aluminium

C. Iron

D. Zinc

Answer: A. Mercury

16. Iron commonly occurs in nature in the form of:

A. Oxides

B. Noble gases

C. Pure liquid

D. Organic compounds only

Answer: A. Oxides

17. Which metal is highly reactive?

A. Gold

B. Silver

C. Potassium

D. Platinum

Answer: C. Potassium

18. Highly reactive metals form compounds readily because they:

A. Are chemically inert

B. React easily with other substances

C. Cannot lose electrons

D. Never react with oxygen

Answer: B

19. Which is an ore of aluminium?

A. Bauxite

B. Haematite

C. Cinnabar

D. Zinc blende

Answer: A. Bauxite

20. Which is an ore of iron?

A. Bauxite

B. Haematite

C. Zinc blende

D. Cinnabar

Answer: B. Haematite

21. Which is an ore of zinc?

A. Haematite

B. Bauxite

C. Zinc blende

D. Cinnabar

Answer: C. Zinc blende

22. Which is an ore of mercury?

A. Cinnabar

B. Bauxite

C. Haematite

D. Copper pyrites

Answer: A. Cinnabar

23. Which metal is least likely to be found in combined form due to very low reactivity?

A. Gold

B. Sodium

C. Potassium

D. Calcium

Answer: A. Gold

24. The major difference between mineral and ore is:

A. Colour

B. Economic feasibility of extraction

C. Physical state

D. Temperature

Answer: B

25. Which sequence is logically correct?

A. Ore → Metal extraction

B. Metal → Ore → Mineral

C. Ore → Non-metal only

D. Mineral → Always pure metal

Answer: A

26. Which metal is generally found in combined form?

A. Gold

B. Platinum

C. Sodium

D. Silver

Answer: C. Sodium

27. The main reason gold can occur in native form is its:

A. High reactivity

B. Low reactivity

C. High melting point only

D. High density only

Answer: B. Low reactivity

28. An ore generally contains:

A. No useful metal

B. Sufficient useful metal for economical extraction

C. Only water

D. Only non-metals

Answer: B

29. Which statement is scientifically most accurate?

A. All minerals are pure metals

B. All ores are minerals suitable for economical metal extraction

C. Ores contain no impurities

D. Metals occur only in free state

Answer: B

30. Which concept is most important in identifying an ore?

A. Economic extraction

B. Colour only

C. Shape only

D. Hardness only

Answer: A. Economic extraction

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30 Subjective Questions – Complete Solutions

1 Mark Questions

Q1. What is a mineral?

A mineral is a naturally occurring element or compound found in the Earth's crust.

खनिज पृथ्वी की भूपर्पटी में प्राकृतिक रूप से पाया जाने वाला तत्व या यौगिक है।

Q2. What is an ore?

An ore is a mineral from which a metal can be extracted economically.

Q3. Give one example of an ore of aluminium.

Bauxite.

Q4. Name an important ore of iron.

Haematite (Fe₂O₃).

Q5. Name an ore of zinc.

Zinc blende (ZnS).

2 Mark Questions

Q6. Define mineral and ore.

Mineral: Naturally occurring substance containing a metal or its compound.

Ore: A mineral from which metal can be extracted economically.

Q7. Why is every mineral not an ore?

Every mineral does not contain sufficient amount of the metal or may not allow economical extraction. Therefore, every mineral is not an ore.

Q8. Why are highly reactive metals generally found in combined state?

Highly reactive metals readily react with oxygen, water, sulphur and other elements. Therefore, they generally occur as stable compounds.

Q9. Why can gold occur in free state?

Gold is very less reactive and does not readily react with other elements. Therefore, it can occur in the free/native state.

Q10. State the relationship between minerals and ores.

All ores are minerals, but all minerals are not ores.

3 Mark Questions

Q11. Differentiate between minerals and ores.

Minerals: Naturally occurring substances that may contain metals or their compounds.

Ores: Minerals from which metals can be extracted conveniently and economically.

Thus, an ore is a useful mineral for metal extraction.

Q12. Explain the occurrence of metals in free and combined states.

Less reactive metals such as gold may occur in free state.

Highly reactive metals such as sodium and potassium generally occur in combined state as compounds.

The difference is mainly due to their reactivity.

Q13. Give three examples of ores and their metals.

1. Bauxite → Aluminium
2. Haematite → Iron
3. Zinc blende → Zinc

Q14. What makes a mineral an ore?

A mineral becomes an ore when the desired metal can be extracted from it conveniently and economically.

Q15. Why is economic feasibility important in defining an ore?

Metal extraction involves mining, concentration, chemical processing and refining. If the cost is too high compared with the value of the metal, the mineral is not considered a useful ore.

4 Mark Questions

Q16. Explain the difference between mineral and ore with examples.

A mineral is a naturally occurring substance containing a metal or its compound.

An ore is a mineral from which the metal can be extracted economically.

For example, bauxite is an important mineral and ore of aluminium because aluminium can be extracted from it economically.

Thus, all ores are minerals but all minerals are not ores.

Q17. Explain why highly reactive metals are not generally found in free state.

Highly reactive metals have a strong tendency to react with other substances. They readily combine with oxygen, sulphur, water or halogens and form stable compounds.

Therefore, metals such as sodium, potassium and calcium generally occur in combined form.

Q18. Explain why less reactive metals can occur in free state.

Less reactive metals have little tendency to react with other substances. Therefore, they may remain uncombined in nature.

Examples include gold and platinum, which can occur in native form.

Q19. Write four important ores and the metals obtained from them.

1. Bauxite → Aluminium
2. Haematite → Iron
3. Zinc blende → Zinc
4. Cinnabar → Mercury

Q20. Explain the importance of reactivity in the occurrence of metals.

The more reactive a metal is, the more readily it combines with other elements. Therefore highly reactive metals are generally found in combined form.

Less reactive metals have a lower tendency to react and may occur in free state.

5 Mark Questions

Q21. Give a detailed explanation of minerals and ores.

Minerals are naturally occurring elements or compounds found in the Earth's crust.

They may contain useful metals along with impurities.

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

Therefore:

Mineral: Natural substance containing metal or its compound.
Ore: Mineral suitable for economical extraction of metal.

Examples include bauxite for aluminium and haematite for iron.

Q22. Differentiate between minerals and ores on five points.

1. Definition: Mineral is a naturally occurring substance; ore is a mineral suitable for metal extraction.

2. Economic value: A mineral may not be economically useful; an ore is economically useful.

3. Metal concentration: A mineral may contain insufficient metal; an ore contains suitable concentration.

4. Extraction: Extraction from an ordinary mineral may not be economical; extraction from an ore is practical.

5. Relationship: All ores are minerals, but all minerals are not ores.

Q23. Explain the occurrence of metals in nature with suitable examples.

Metals occur in nature in free or combined states.

Free state: Less reactive metals such as gold and platinum may occur in native form.

Combined state: Reactive metals occur as compounds such as oxides, sulphides, carbonates or halides.

Examples:
Iron – haematite
Zinc – zinc blende
Aluminium – bauxite

The form in which a metal occurs depends mainly on its reactivity.

Q24. Explain the meaning of economical extraction of metals.

Economical extraction means that the cost of obtaining the metal from the mineral is reasonable compared with the value of the metal obtained.

The mineral must contain sufficient useful metal and should be capable of being processed by practical methods.

Such a mineral is called an ore.

Q25. Explain the relationship among mineral, ore and metal.

A metal occurs naturally in the Earth's crust in different minerals.

Some minerals contain enough metal and allow economical extraction. These are called ores.

The ore is processed to obtain the metal.

Therefore:

Mineral → Suitable Mineral/Ore → Extraction → Metal

6 Mark Questions

Q26. Explain in detail the difference between minerals and ores.

Minerals:
Minerals are naturally occurring elements or compounds found in the Earth's crust. They may contain metals in different concentrations and may contain several impurities.

Ores:
Ores are minerals from which metals can be extracted conveniently and economically.

Main differences:
1. Every ore is a mineral.
2. Every mineral is not an ore.
3. Ore must have sufficient useful metal or a suitable form for extraction.
4. Extraction from an ore must be economically feasible.
5. Ordinary minerals may not be suitable for profitable extraction.
6. Examples include bauxite for aluminium and haematite for iron.

Q27. Explain how the reactivity of metals affects their occurrence in nature.

The occurrence of metals is strongly related to their chemical reactivity.

Highly reactive metals:
They readily react with oxygen, water, sulphur and halogens. Hence they are generally found in combined form.
Examples: Sodium, potassium and calcium.

Moderately reactive metals:
They generally occur as compounds such as oxides, sulphides and carbonates.
Examples: Iron, zinc and copper.

Less reactive metals:
They may occur in free/native state.
Examples: Gold and platinum.

Thus, greater reactivity generally means a greater tendency to occur in combined form.

Q28. Explain with examples why all minerals cannot be called ores.

A mineral is a naturally occurring substance containing a metal or its compound. However, extraction of metal from every mineral is not economically feasible.

A mineral may contain a very small amount of metal, require complicated processing, or involve excessive cost.

Only those minerals from which metal can be extracted conveniently and economically are called ores.

Therefore:

All ores ⊂ Minerals

but:
All minerals ≠ Ores

Q29. Write an exam-oriented note on important ores of metals.

1. Aluminium: Bauxite is the principal ore of aluminium.

2. Iron: Haematite (Fe₂O₃) is an important ore of iron.

3. Zinc: Zinc blende (ZnS) is an important ore of zinc.

4. Copper: Copper pyrites (CuFeS₂) is an important ore of copper.

5. Mercury: Cinnabar (HgS) is an important ore of mercury.

These ores are processed to extract their respective metals.

Q30. “All ores are minerals but all minerals are not ores.” Explain this statement with examples.

Minerals are naturally occurring substances containing metals or their compounds.

When a mineral contains sufficient useful metal and the metal can be extracted conveniently and economically, the mineral is classified as an ore.

For example, bauxite is an ore of aluminium because aluminium can be extracted from it economically. Haematite is an important ore of iron.

However, a naturally occurring mineral may contain too little metal or may be too expensive to process. Such a mineral is not considered a useful ore.

Therefore, the correct conclusion is:

Every ore is a mineral, but every mineral is not an ore.

Class 10 Science | Occurrence of Metals
Minerals + Ores + Differences + Occurrence + 30 MCQs + 30 Subjective Questions