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1. L6
METALS AND
NON-METALS
CLASS X - SCIENCE
PRASHANT KIRAD

2. Refining of Metals

3. Refining of Metals
The metals produced by various reduction processes described
above are not very pure. They contain impurities, which must be
removed to obtain pure metals.
Impurities can be removed by various processes like:
Electrolytic refining
Distillation
Liquefaction
Vapor phase refining
Zone refining

4. Electrolytic refining
In this process, the impure metal is made the
anode.
A thin strip of pure metal is made the cathode.
A solution of the metal salt is used as an
electrolyte.
On passing current through the electrolyte, the
pure metal from the anode dissolves into the
electrolyte.
An equivalent amount of pure metal from the
electrolyte is deposited on the cathode.
Soluble impurities go into the solution.
Insoluble impurities settle down at the bottom of
the anode and are known as anode mud.

5. Electrolytic refining of copper
i. The set-up consists of an electrolytic tank that
contains acidified copper sulphate solution.
ii. A thick block of impure copper metal is
connected to the positive terminal.
iii. A thin strip of pure copper metal is
connected to the negative terminal.
iv. At cathode, reduction will happen and at
anode, oxidation will occur.
v. As the process continues, anode will become
thinner & cathode will become thicker.
Ab toh smajh
gye hoge

6. Question
practise
karo!

7. QUES. Which of the following metals is extracted by electrolytic
reduction? [CBSE 2014, 2019, 2021]
A. Iron
B. Zinc
C. Sodium
D. Copper

8. QUES.Which of the following is not used in the extraction of iron from
haematite? [2020]
A. Limestone
B. Coke
C. Cryolite
D. Air

9. QUES.Which of the following is an amphoteric oxide? [CBSE 2015, 2021]
A. Na₂O
B. ZnO
C. CO₂
D. CaO

10. QUES. Assertion (A): Ionic compounds conduct electricity in molten state.
Reason (R): Ions are free to move in the molten state of ionic compounds.
[CBSE Term 1, 2021–22]
Options:
A. Both A and R are true, and R is the correct explanation of A.
B. Both A and R are true, but R is not the correct explanation of A.
C. A is true but R is false.
D. A is false but R is true.

11. QUES. Assertion (A): Carbon is used for the extraction of zinc from zinc
oxide.
Reason (R): Zinc is more reactive than carbon. [CBSE 2015, 2020]
Options:
A. Both A and R are true, and R is the correct explanation of A.
B. Both A and R are true, but R is not the correct explanation of A.
C. A is true but R is false.
D. A is false but R is true.

12. QUES. Case-Based Questions [CBSE 2014, 2020, 2022]
Case: Thermite Reaction (Al + Fe₂O₃ → Fe + Al₂O₃)
A blacksmith uses a highly exothermic reaction to join railway tracks. The
reaction used is:
Aluminium powder + Iron (III) oxide → ?
(a) Name this reaction.
(b) Which metal acts as a reducing agent?
(c) Why is this reaction useful in welding?
(a) Thermite reaction / Alumino-thermic reaction
(b) Aluminium
(c) It is highly exothermic and produces molten iron which is used to weld
railwaytracks

13. QUES. Case Study [CBSE 2015, 2020, 2023]
Copper is refined electrolytically. In this process:
(a) What is used as the anode and cathode?
(b) What is the electrolyte?
(c) What happens to the impurities?
(a) Anode – Impure copper rod, Cathode – Pure copper rod
(b) Electrolyte – Acidified copper sulphate solution (CuSO₄ + H₂SO₄)
(c) Impurities either dissolve in the solution or settle down at the bottom of
the cell as anode mud.
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14. QUES. Why is electrolytic reduction used to extract metals high up in the
reactivity series? [2013, 2015, 2020, 2023]
Metals high up in the reactivity series, like sodium, potassium, calcium,
and aluminium, are very reactive. Their ores are very stable and cannot be
reduced using common reducing agents like carbon. Therefore, electrolytic
reduction is used, as it provides the necessary energy to break the strong
bonds in their compounds and extract the pure metal.

15. QUES. Explain the extraction of sodium from molten sodium chloride with
chemical reactions. [2012, 2013, 2020, 2023]
Sodium is extracted from molten sodium chloride by electrolysis.
At cathode (–): Sodium ions gain electrons to form sodium metal.
Na⁺ + e⁻ → Na
At anode (+): Chloride ions lose electrons to form chlorine gas.
2Cl⁻ → Cl₂ + 2e⁻
So, sodium metal is collected at the cathode and chlorine gas is released at
the anode.

16. QUES. Why can't carbon be used to reduce oxides of metals like sodium
and aluminium? [2013, 2015, 2020, 2023]
Carbon cannot be used to reduce the oxides of metals like sodium and
aluminium because these metals are very reactive and form very stable
oxides. Carbon is not reactive enough to displace such highly reactive
metals from their compounds. Therefore, electrolytic reduction is used to
extract these metals.

17. QUES. Why are sulphide and carbonate ores converted into oxides before
reduction? [Repeated 2013, 2015, 2019, 2022]
Sulphide and carbonate ores are converted into oxides before reduction
because metal oxides can be easily reduced to metals, whereas sulphides
and carbonates are not easily reduced. This conversion is done by:
Roasting (for sulphide ores)
Calcination (for carbonate ores)
This step makes the extraction of the metal easier and more efficient.

18. QUES. Explain electrolytic refining of copper with labelled diagram.
[2013, 2015, 2018, 2020, 2024]
Electrolytic Refining of Copper:
In this process, impure copper is refined using electricity.
Anode (positive electrode): Impure copper rod
Cathode (negative electrode): Pure copper rod
Electrolyte: Acidified copper sulphate solution (CuSO₄ + H₂SO₄)
Process:
On passing electric current:
Copper from the anode dissolves into the solution as Cu²⁺ ions.
These ions move to the cathode and get deposited as pure copper.
Impurities either dissolve or settle at the bottom as anode mud.
Chemical reactions:
At anode: Cu → Cu²⁺ + 2e⁻
At cathode: Cu²⁺ + 2e⁻ → Cu

19. QUES. Explain electrolytic reduction with suitable example.
[2015, 2018, 2020, 2023]
Electrolytic reduction is the process of extracting a metal from its compound
using electric current. This method is used for highly reactive metals like sodium,
potassium, calcium, and aluminium, whose oxides or chlorides are very stable
and cannot be reduced by common reducing agents like carbon.
Example: Extraction of Sodium from Molten NaCl
Cathode (–): Sodium ions gain electrons (reduction)
Na⁺ + e⁻ → Na
Anode (+): Chloride ions lose electrons (oxidation)
2Cl⁻ → Cl₂ + 2e⁻
Thus, sodium metal is obtained at the cathode by electrolytic reduction.

20. QUES. Explain the setup with a well-labelled diagram. State the roles of
electrolyte, anode, and cathode, and write the reactions involved at each
electrode. [CBSE 2013, 2015, 2020, 2023, 2024]
Roles:
Electrolyte: Acidified copper sulphate (CuSO₄ + H₂SO₄); supplies Cu²⁺ ions and allows current
flow.
Anode (+): Impure copper rod; loses copper atoms which go into solution as Cu²⁺.
Cathode (–): Pure copper rod; gains Cu²⁺ ions from solution, which get deposited as pure
copper.
Reactions:
At Anode (Oxidation):
Cu → Cu²⁺ + 2e⁻
At Cathode (Reduction):
Cu²⁺ + 2e⁻ → Cu

21. CORROSION

22. Corrosion is a natural process where a metal surface deteriorates due to
interaction with substances like air or water.
A common example is the rusting of iron,
caused by exposure to air and moisture,
forming a reddish-brown substance (Fe₃O₄).

23. Due to corrosion, the metal's lustrous surface fades away.
Metal shine Before corrosion
Metal shine fades away after corrosion

24. TYPES OF CORROSION

25. When iron comes in contact with moist air, it forms hydrated ferric oxide.
This oxide has a reddish-brown color.
RUSTING OF IRON

26. Copper reacts with moist carbon dioxide from the air to produce copper
carbonate. This reaction results in a green layer forming on its surface.
Tarnishing of Copper

27. Silver reacts with hydrogen sulphide in the atmosphere to form
silver sulphide, which gives it a black coating.
Tarnishing of Silver

28. Patina (Advantageous Corrosion):
Corrosion can sometimes be beneficial. For example,
copper develops a protective green layer called
patina after oxidation.
This layer acts as a barrier that prevents further
corrosion.
Patina

29. PREVENTION OF
CORROSION

30. To stop metals like iron from rusting, three primary techniques are used:
a) Using a protective barrier
b) Sacrificial protection
c) Alloying metals

31. This approach involves placing a protective coating over iron to block rust-
causing agents like air and water vapor.
Common methods include:
i. Painting the surface
ii. Lubricating with oil or grease

32. This technique uses a more reactive metal to shield a less reactive one.
The reactive metal corrodes instead of iron, thus offering protection.
Galvanization:
A technique where a thin zinc layer is applied
to steel or iron. Even if the coating breaks, the
zinc still protects against rust.

33. Sheets of galvanized iron are commonly used to make:
i. Water buckets
ii. Storage drums
iii. Roofing sheets

34. Alloying involves mixing two or more metals (and sometimes non-metals)
to create a new, enhanced material.
It is a permanent method to guard against rust and offers several benefits:
Boosts hardness
Improves strength
Lowers melting point
Enhances rust resistance
Reduces electric conductivity

35. Pure iron is weak and rusts easily. By mixing it with carbon, it turns stronger
and more durable.
Example:
Stainless Steel = Iron + Chromium + Nickel
Chromium resists corrosion and stains
Nickel adds hardness
Fun fact: If mercury is one of the metals, the mixture is called an amalgam.

36. Pure gold, known as 24 carat gold, is very soft. It is, therefore, not
suitable for making jewellery. It is alloyed with either silver or copper to
make it hard. Generally, in India, 22 carat gold is used for making
ornaments. It means that 22 parts of pure gold is alloyed with 2 parts of
either copper or silver.

37. Alloys usually conduct less electricity and melt at lower temperatures
than pure metals.
Examples:
Brass (Copper + Zinc) and Bronze (Copper + Tin) don’t conduct
electricity well, unlike pure copper.
Solder (Lead + Tin) melts easily and is ideal for joining wires.

38. The iron pillar near the Qutub Minar in Delhi was built more than 1600
years ago by the iron workers of India. They had developed a process
which prevented iron from rusting. For its quality of rust resistance it has
been examined by scientists from all parts of the world. The iron pillar is
8 m high and weighs 6 tonnes (6000 kg).

39. QUES. Galvanization prevents rusting by coating iron with: [CBSE 2022]
A) Lead
B) Silver
C) Zinc
D) Copper

40. QUES. Rusting of iron occurs in the presence of: [CBSE 2019 , 2023]
A) Air only
B) Water only
C) Both air and water
D) Salt

41. QUES. Stainless steel does not rust because: [2023, 2017]
A) It is magnetic
B) It is an alloy
C) It is soft
D) It is coated with paint

42. QUES. Why do aluminium articles not corrode easily? [2019, 2021]
Aluminium forms a thin layer of aluminium oxide on its surface which
prevents further corrosion.

43. QUES. Why does an iron nail rust in tap water but not in boiled distilled
water? [2022]
Tap water contains dissolved oxygen and minerals that support rusting,
while boiled distilled water lacks oxygen and salts.

44. QUES. Why are ships painted frequently?
Because salt water accelerates corrosion; painting prevents direct contact
of iron with salty moisture.

45. QUES. Why are food cans coated with tin and not with zinc? [CBSE 2018]

Zinc is more reactive and can contaminate food.
Tin is less reactive and safer for food storage.

46. QUES. Assertion (A): Rusting of iron is a chemical change.
Reason (R): A new substance, iron oxide, is formed during rusting.
[CBSE 2021]

47. QUES. Assertion (A): Aluminium does not corrode easily.
Reason (R): Aluminium forms a protective layer of aluminium oxide on its
surface.

48. QUES. Assertion (A): Painting and greasing help to prevent corrosion of
iron.
Reason (R): They prevent oxygen and moisture from coming in contact with
the surface of the metal.
[CBSE 2019]

49. Chapter Khatam!!!!!!