CH:8 Metallurgy Class 10th Solutions | Metallurgy SSC Class 10 Questions And Answers

Metallurgy Class 10th Solutions | Metallurgy SSC Class 10 Questions And Answers

Exercises | Q 1.1 | Page 108

Write name.
Alloy of sodium with mercury.

Solution 1: Scientific and Written Exam Answer

The alloy of sodium with mercury is called Sodium Amalgam.

Solution 2: Simple and Understandable Answer

When sodium is mixed with mercury, it forms an alloy known as Sodium Amalgam. It is commonly used in chemical reactions and laboratory experiments. OR Sodium amalgam, commonly denoted as Na(Hg), it is an alloy of mercury and sodium.

Exercises | Q 1.2 | Page 108

Write name.
Molecular formula of the common ore of aluminium.

Solution 1: Scientific and Written Exam Answer

The most common ore of aluminium is Bauxite, and its molecular formula is:

$$ \text{Al}_2\text{O}_3 \cdot 2\text{H}_2\text{O} $$

Solution 2: Simple and Understandable Answer

The main source of aluminium is a mineral called Bauxite. Its chemical formula is Al₂O₃·2H₂O, which means it consists of aluminium oxide combined with water molecules.

Exercises | Q 1.3 | Page 108

Write name.
The oxide that forms salt and water by reacting with both acid and base.

Solution 1: Scientific and Written Exam Answer

The oxide that reacts with both acids and bases to form salt and water is called an Amphoteric Oxide. An example of such an oxide is Aluminium Oxide (Al₂O₃).

Solution 2: Simple and Understandable Answer

Some oxides can react with both acids and bases to form salt and water. These are called Amphoteric Oxides. A common example is Aluminium Oxide (Al₂O₃), which shows this dual behavior.

Exercises | Q 1.4 | Page 108

Write name.
The device used for grinding an ore.

Solution 1: Scientific and Written Exam Answer

The device used for grinding an ore into fine particles is called a Ball Mill.

Solution 2: Simple and Understandable Answer

To break down ore into small pieces for further processing, a machine called a Ball Mill is used. It helps in grinding the ore into a fine powder.

Exercises | Q 1.5 | Page 108

Write name.
The nonmetal having electrical conductivity.

Solution 1: Scientific and Written Exam Answer

Graphite is a nonmetal that has electrical conductivity due to the presence of free-moving electrons in its structure.

Solution 2: Simple and Understandable Answer

The only nonmetal that can conduct electricity is Graphite. This happens because it has free electrons that allow the flow of electric current.

Exercises | Q 1.6 | Page 108

Write name.
The reagent that dissolves noble metals.

Solution 1: Scientific and Written Exam Answer

The reagent that can dissolve noble metals like gold (Au) and platinum (Pt) is called Aqua Regia. It is a highly corrosive mixture of concentrated hydrochloric acid (HCl) and nitric acid (HNO₃) in a 3:1 ratio.

Solution 2: Simple and Understandable Answer

A special acid mixture called Aqua Regia is used to dissolve noble metals like gold and platinum. It is made by mixing 3 parts of hydrochloric acid (HCl) and 1 part of nitric acid (HNO₃).

Exercises | Q 2 | Page 108

Make pairs of substances and their properties.

Substance	Property
a. Potassium bromide (KBr)	1. Combustible
b. Gold	2. Soluble in water
c. Sulphur	3. No chemical reaction
d. Neon	4. High ductility.

Solution:

Substance	Correct Property
a. Potassium bromide (KBr)	2. Soluble in water
b. Gold	4. High ductility
c. Sulphur	1. Combustible
d. Neon	3. No chemical reaction

Exercises | Q 3 | Page 109

Identify the pairs of metals and their ores from the following.

Group A (Ores)	Group B (Metals)
a. Bauxite	i. Mercury
b. Cassiterite	ii. Aluminium
c. Cinnabar	iii. Tin

Solution:

Ore	Correct Metal
a. Bauxite	ii. Aluminium
b. Cassiterite	iii. Tin
c. Cinnabar	i. Mercury

Exercises | Q 4.1 | Page 109

Explain the term Metallurgy.

Solution 1: Scientific and Written Exam Answer

Metallurgy is the branch of science and technology that deals with the study of metals, their extraction from ores, refining, and production of useful alloys. It involves various processes such as:

• Ore Concentration: Removing impurities from the ore.
• Extraction: Obtaining pure metal from the concentrated ore through chemical and electrochemical methods.
• Refining: Purification of the extracted metal to improve its properties.
• Alloying: Mixing metals with other elements to enhance strength and durability.

Metallurgy plays a crucial role in industries such as construction, electronics, and manufacturing.

Solution 2: Simple and Understandable Answer

Metallurgy is the process of obtaining metals from their ores and making them useful for different purposes. It includes:

• Removing unwanted substances from the ore.
• Extracting pure metal using heat or electricity.
• Cleaning the metal to make it strong and useful.
• Mixing metals with other elements to make them better.

Example: Iron is extracted from its ore and used to make steel for buildings and vehicles.

Exercises | Q 4.2 | Page 109

Explain the term Ores.

Solution 1: Scientific and Written Exam Answer

Ores are naturally occurring rocks or minerals from which metals can be extracted profitably. They contain a high concentration of a particular metal along with impurities known as gangue. The process of extracting metals from ores involves several steps such as:

• Mining: Ores are obtained from the Earth's crust through mining.
• Concentration: Removing unwanted impurities from the ore.
• Extraction: Obtaining metal from the ore using chemical or physical processes.

Example: Bauxite (Al₂O₃·2H₂O) is an ore of Aluminium.

Solution 2: Simple and Understandable Answer

Ores are rocks or minerals from which metals can be taken out and used. They contain both the metal and some unwanted materials (impurities).

• Ores are dug from the earth by mining.
• The useful metal is separated from unwanted materials.
• These metals are then used in daily life.

Example: Iron is extracted from Hematite ore (Fe₂O₃).

Exercises | Q 4.3 | Page 109

Explain the term Minerals.

Solution 1: Scientific and Written Exam Answer

Minerals are naturally occurring inorganic substances found in the Earth's crust. They contain various elements or compounds in a definite chemical composition and crystalline structure. Some minerals are used as ores for metal extraction.

• Composition: Minerals can be composed of a single element or a combination of elements.
• Types: Metallic minerals (e.g., Hematite - Fe₂O₃) and Non-metallic minerals (e.g., Quartz - SiO₂).
• Uses: Minerals are essential for industries, construction, and daily life applications.

Example: Bauxite (Al₂O₃·2H₂O) is a mineral of Aluminium.

Solution 2: Simple and Understandable Answer

Minerals are natural substances found in rocks, soil, and water. They contain metals or other useful materials.

• Some minerals are used to make metals.
• Other minerals are used in making glass, bricks, or jewelry.
• Minerals are important for industries and daily life.

Example: Iron is obtained from Hematite mineral (Fe₂O₃).

Exercises | Q 4.4 | Page 109

Explain the term Gangue.

Solution 1: Scientific and Written Exam Answer

Gangue refers to the unwanted, non-valuable impurities like sand, soil, clay, and rock present in an ore. These impurities do not contain any useful metal and must be removed before metal extraction.

• Composition: Gangue consists of non-metallic minerals and waste materials.
• Removal Process: Gangue is separated from the ore using methods like gravity separation, froth flotation, and magnetic separation.
• Importance: The removal of gangue improves the purity and efficiency of metal extraction.

Example: In iron extraction, hematite (Fe₂O₃) ore contains silica (SiO₂) as gangue.

Solution 2: Simple and Understandable Answer

Gangue is the waste material found in ores. It is made of unwanted substances like sand, mud, and rocks.

• Gangue is removed before extracting metals.
• Removing gangue makes metal extraction easier and more efficient.
• Different techniques are used to separate gangue from the useful ore.

Example: In iron ore, the unwanted sand and clay are called gangue.

Exercises | Q 5.1 | Page 109

Write scientific reasons: Lemon or tamarind is used for cleaning copper vessels turned greenish.

Solution:

Copper vessels turn green due to the formation of copper carbonate (CuCO₃) when copper reacts with oxygen, carbon dioxide, and moisture from the air.

• Lemon and tamarind contain acids like citric acid and tartaric acid.
• These acids react with the green copper carbonate layer and dissolve it.
• As a result, the shiny copper surface is restored.

Chemical Reaction:

$$ CuCO₃ + 2HCl \rightarrow CuCl₂ + H₂O + CO₂ $$

Conclusion: The acidic nature of lemon or tamarind helps remove the greenish layer, making the copper vessel clean and shiny again.

Exercises | Q 5.2 | Page 109

Write scientific reason: Generally, the ionic compounds have high melting points.

Solution:

• Ionic compounds are formed by the strong electrostatic force of attraction between oppositely charged ions.
• These forces, known as ionic bonds, are very strong and require a large amount of energy to break.
• Due to these strong bonds, ionic compounds have high melting points compared to covalent compounds.

Example: Sodium chloride (NaCl) has a high melting point of about 801°C due to strong ionic bonding.

Exercises | Q 5.3 | Page 109

Write scientific reason: Sodium is always kept in kerosene.

Solution:

• Sodium is a highly reactive metal that reacts vigorously with oxygen and water present in the air.
• If exposed to moisture, it reacts with water to form sodium hydroxide (NaOH) and hydrogen gas (H₂), which can catch fire.
• To prevent this reaction, sodium is stored in kerosene, which acts as a protective barrier and prevents contact with air and water.

Chemical Reaction:

$$ 2Na + 2H₂O \rightarrow 2NaOH + H₂ ↑ $$

Conclusion: Storing sodium in kerosene ensures its safety by preventing unwanted reactions with moisture and oxygen.

Exercises | Q 5.4 | Page 109

Write scientific reason: Pine oil is used in froth flotation.

Solution:

• Froth flotation is a method used for the concentration of sulphide ores.
• Pine oil is used as a frothing agent (surfactant) in this process.
• It helps in the formation of stable froth by reducing the surface tension of water.
• When air is passed through the mixture, pine oil helps sulphide ore particles to attach to air bubbles and rise to the surface.
• Impurities settle at the bottom, while the concentrated ore is collected from the top.

Conclusion: Pine oil plays a crucial role in separating sulphide ores by making them float on the froth.

Exercises | Q 5.5 | Page 109

Write scientific reason: Anodes need to be replaced from time to time during the electrolysis of alumina.

Solution:

• In the electrolysis of alumina (Hall-Héroult process), the anodes are made of graphite (carbon).
• During electrolysis, oxygen gas is released at the anode.
• The oxygen reacts with carbon anodes to form carbon dioxide (CO₂), gradually wearing them down.
• Due to this continuous consumption of carbon, anodes need to be replaced periodically.

Chemical Reaction:

$$ C + O₂ \rightarrow CO₂ $$

Conclusion: Since the anodes are consumed during the reaction, they must be replaced regularly to maintain the process.

Exercises | Q 6 | Page 109

When a copper coin is dipped in silver nitrate solution, a glitter appears on the coin after some time. Why does this happen? Write the chemical equation.

Solution:

• Copper is more reactive than silver in the reactivity series.
• When a copper coin is placed in silver nitrate (AgNO₃) solution, copper displaces silver from the solution.
• Silver gets deposited on the surface of the copper coin, creating a shiny, glittering appearance.

Chemical Reaction:

$$ Cu + 2AgNO₃ \rightarrow Cu(NO₃)₂ + 2Ag ↓ $$

Conclusion: The glittering effect occurs due to the deposition of silver metal on the copper coin.

Exercises | Q 7 | Page 109

The electronic configuration of metal ‘A’ is 2,8,1 and that of metal ‘B’ is 2,8,2. Which of the two metals is more reactive? Write their reaction with dilute hydrochloric acid.

Solution:

Step 1: Identifying the metals

• Metal ‘A’ has an electronic configuration of 2,8,1, which corresponds to sodium (Na).
• Metal ‘B’ has an electronic configuration of 2,8,2, which corresponds to magnesium (Mg).

Step 2: Comparing Reactivity

• Sodium (Na) belongs to Group 1 (Alkali Metals), while Magnesium (Mg) belongs to Group 2 (Alkaline Earth Metals).
• Since alkali metals are more reactive than alkaline earth metals, sodium (Na) is more reactive than magnesium (Mg).

Step 3: Reaction with Dilute Hydrochloric Acid (HCl)

Reaction of Sodium (Na) with HCl:

$$ 2Na + 2HCl \rightarrow 2NaCl + H_2 ↑ $$

Reaction of Magnesium (Mg) with HCl:

$$ Mg + 2HCl \rightarrow MgCl_2 + H_2 ↑ $$

Conclusion: Sodium (Na) is more reactive than Magnesium (Mg), and both metals react with HCl to release hydrogen gas.

Exercises | Q 8.1 | Page 109

Draw a neat labelled diagram.

Magnetic Separation Method

Solution:

The Magnetic Separation Method is used to separate magnetic ores from non-magnetic impurities using a magnet. It is commonly used in the beneficiation of iron ores.

Principle: This method works on the principle that magnetic substances are attracted to a magnet, while non-magnetic substances remain unaffected.

Diagram:

Exercises | Q 8.2 | Page 109

Draw a neat labelled diagram.

Froth Flotation Method

Solution:

The Froth Flotation Method is a process used for separating hydrophobic (water-repelling) and hydrophilic (water-attracting) materials. It is mainly used to extract sulphide ores such as zinc blende (ZnS) and copper pyrites (CuFeS₂).

Principle: The ore particles are wetted by oil, while the gangue (impurities) is wetted by water. A frothing agent is added to create foam, which helps the ore particles float and separate from the gangue.

Diagram:

Exercises | Q 8.3 | Page 109

Draw a neat labelled diagram.

Electrolytic Reduction of Alumina

Solution:

The Electrolytic Reduction of Alumina is an industrial method used to extract pure aluminium from bauxite ore using electrolysis. This process is also known as the Hall-Héroult Process.

Principle: Alumina (Al₂O₃) is dissolved in molten cryolite (Na₃AlF₆) and electrolyzed in a specially designed electrolytic cell. Aluminium metal is deposited at the cathode, while oxygen is released at the anode.

Diagram:

Exercises | Q 8.4 | Page 109

Draw a neat labelled diagram.

Hydraulic Separation Method

Solution:

The Hydraulic Separation Method, also known as Gravity Separation, is a process used to separate heavier ore particles from lighter impurities using a stream of water.

Principle: The method is based on the difference in the densities of ore and gangue. The heavier ore particles settle at the bottom while the lighter gangue is washed away.

Diagram:

Exercises | Q 9.1 | Page 109

Write the chemical equation for the event: Aluminium came in contact with air.

Solution 1: Scientific and Written Exam Answer

When aluminium (Al) comes in contact with air, it reacts with oxygen (O₂) to form a thin, protective layer of aluminium oxide (Al₂O₃). This layer prevents further oxidation of aluminium.

Chemical Equation:

$$ 4Al + 3O_2 \rightarrow 2Al_2O_3 $$

Explanation:

• Aluminium is highly reactive with oxygen.
• It forms a strong, adherent layer of aluminium oxide (Al₂O₃), which prevents further corrosion.

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Solution 2: Simple and Understandable Answer

When aluminium is exposed to air, it reacts with oxygen and forms a protective coating of aluminium oxide.

Example:

• Think of aluminium utensils or foil. They do not rust like iron because of this protective oxide layer.
• This coating prevents aluminium from further damage and increases its durability.

Exercises | Q 9.2 | Page 109

Write the chemical equation for the event: Iron filings are dropped in an aqueous solution of copper sulphate.

Solution 1: Scientific and Written Exam Answer

Iron (Fe) is more reactive than copper (Cu). When iron filings are added to an aqueous solution of copper sulfate (CuSO₄), iron displaces copper from the solution, forming iron sulfate (FeSO₄) and depositing copper metal.

Chemical Equation:

$$ Fe + CuSO_4 \rightarrow FeSO_4 + Cu $$

Explanation:

• This is a displacement reaction where iron replaces copper from its sulfate solution.
• The blue color of copper sulfate solution fades as copper is displaced.
• A brownish-red deposit of copper forms on the iron filings.

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Solution 2: Simple and Understandable Answer

When iron is added to a blue-colored copper sulfate solution, the iron starts reacting with it. Iron takes the place of copper in the solution, turning it light green as iron sulfate forms, while copper settles as a brownish layer.

Example:

• If you dip an iron nail in copper sulfate solution, the nail will get a reddish layer of copper.
• The blue solution turns pale green due to the formation of iron sulfate.

Exercises | Q 9.3 | Page 109

Write the chemical equation for the event: A reaction was brought about between ferric oxide and aluminum.

Solution 1: Scientific and Written Exam Answer

Ferric oxide (Fe₂O₃) reacts with aluminum (Al) in a highly exothermic displacement reaction known as the Thermite Reaction. Here, aluminum reduces iron oxide to molten iron, which is useful in welding railway tracks.

Chemical Equation:

$$ Fe_2O_3 + 2Al \rightarrow 2Fe + Al_2O_3 + \text{Heat} $$

Explanation:

• Aluminum, being more reactive, displaces iron from iron oxide.
• The reaction generates intense heat, causing iron to become molten.
• This is an example of a redox reaction used in industrial applications.

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Solution 2: Simple and Understandable Answer

When aluminum powder is mixed with ferric oxide (rust) and ignited, it produces molten iron and aluminum oxide. This reaction is extremely hot and is used to weld railway tracks.

Example:

• It is used in railway repair work to join broken metal parts.
• The reaction produces bright sparks and a large amount of heat.

Exercises | Q 9.4 | Page 109

Write the chemical equation for the event: Electrolysis of alumina is done.

Solution 1: Scientific and Written Exam Answer

The electrolysis of alumina (Al₂O₃) is carried out using the Hall-Héroult process. In this method, alumina is dissolved in molten cryolite (Na₃AlF₆) to lower the melting point. The electrolysis occurs in a carbon-lined cell, with carbon electrodes serving as the anode and cathode.

Chemical Equations:

At Cathode (Reduction):

$$ Al^{3+} + 3e^- \rightarrow Al $$

At Anode (Oxidation):

$$ 2O^{2-} \rightarrow O_2 + 4e^- $$

Overall Reaction:

$$ 2Al_2O_3 \rightarrow 4Al + 3O_2 $$

Explanation:

• Aluminum ions gain electrons at the cathode and form pure aluminum.
• Oxygen ions lose electrons at the anode, forming oxygen gas.
• The carbon anode reacts with oxygen, forming CO₂, which is why anodes need frequent replacement.

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Solution 2: Simple and Understandable Answer

Alumina (Al₂O₃) is broken down into aluminum and oxygen gas using electricity. The aluminum collects at the bottom, and oxygen is released as gas.

Example:

• This process is used in aluminum factories to extract pure aluminum from its ore.
• Oxygen gas escapes into the air, while liquid aluminum is collected for making metal products.

Exercises | Q 9.5 | Page 109

Write a chemical equation for the following event: Zinc oxide is dissolved in dilute hydrochloric acid.

Solution 1: Scientific and Written Exam Answer

Zinc oxide (ZnO) is an amphoteric oxide, meaning it reacts with both acids and bases. When ZnO reacts with dilute hydrochloric acid (HCl), it forms zinc chloride (ZnCl₂) and water (H₂O).

Chemical Equation:

$$ ZnO + 2HCl \rightarrow ZnCl_2 + H_2O $$

Explanation:

• Zinc oxide (ZnO) is a metal oxide that dissolves in hydrochloric acid, producing zinc chloride.
• Water (H₂O) is formed as a byproduct.
• This is a neutralization reaction where the basic zinc oxide reacts with an acid.

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Solution 2: Simple and Understandable Answer

When zinc oxide (a white powder) is mixed with hydrochloric acid, it dissolves and forms zinc chloride (a salt) and water.

Example:

• This reaction is similar to how lime (calcium oxide) reacts with acids.
• Zinc chloride is used in batteries and other chemical processes.

Exercises | Q 10.1 | Page 109

Complete the statement using every given option: During the extraction of aluminium... Ingredients and gangue in bauxite.

Solution 1: Scientific and Written Exam Answer

During the extraction of aluminium, bauxite (Al₂O₃·xH₂O) is the primary ore used. It contains aluminium oxide along with impurities (gangue), such as silica (SiO₂), iron oxides (Fe₂O₃), and titanium dioxide (TiO₂).

Ingredients in Bauxite:

• Aluminium oxide (Al₂O₃) - The main component used for aluminium extraction.
• Water of hydration (xH₂O) - Found in the bauxite mineral.

Gangue (Impurities) in Bauxite:

• Silica (SiO₂)
• Iron oxide (Fe₂O₃)
• Titanium dioxide (TiO₂)

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Solution 2: Simple and Understandable Answer

Bauxite is the main ore used to extract aluminium. It contains a useful ingredient called aluminium oxide (Al₂O₃) and some unwanted impurities.

Useful Part: Aluminium oxide (Al₂O₃)

Impurities (Gangue):

• Sand (Silica - SiO₂)
• Rust-like iron compounds (Fe₂O₃)
• Other unwanted materials like titanium dioxide (TiO₂)

Example: Just like we remove pebbles from rice before cooking, we need to remove impurities from bauxite before extracting aluminium.

Exercises | Q 10.2 | Page 109

Complete the statement using every given option: During the extraction of aluminium... Use of leaching during the concentration of ore.

Solution 1: Scientific and Written Exam Answer

Leaching is a chemical process used to remove impurities from bauxite ore during aluminium extraction. In this method, powdered bauxite (Al₂O₃·xH₂O) is treated with concentrated sodium hydroxide (NaOH) solution at high temperature and pressure.

Chemical Reaction:

$$ Al_2O_3 + 2NaOH + 3H_2O \rightarrow 2Na[Al(OH)_4] $$

The aluminium oxide (Al₂O₃) dissolves in NaOH, forming sodium aluminate (Na[Al(OH)₄]). Impurities like Fe₂O₃ and SiO₂ remain undissolved and are removed by filtration. Later, aluminium hydroxide is precipitated by adding CO₂ gas, which is then calcined to obtain alumina (Al₂O₃).

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Solution 2: Simple and Understandable Answer

Leaching is a method used to purify bauxite ore. In this process, the useful aluminium compound dissolves in a special liquid (sodium hydroxide), leaving behind unwanted dirt.

Step-by-Step Process:

• The ore is mixed with NaOH, which dissolves aluminium oxide.
• Unwanted impurities (like sand and iron oxide) are removed.
• Aluminium is then recovered by adding a gas (CO₂).
• Finally, the aluminium compound is heated to form pure alumina.

Example: It’s like washing rice to remove dirt before cooking!

Exercises | Q 10.3 | Page 109

Complete the statement using every given option: During the extraction of aluminium... Chemical reaction of transformation of bauxite into alumina by Hall’s process.

Solution 1: Scientific and Written Exam Answer

In Hall’s process, bauxite (Al₂O₃·xH₂O) is converted into alumina (Al₂O₃) by first dissolving it in sodium hydroxide (NaOH) and then precipitating aluminium hydroxide (Al(OH)₃), which is further heated.

Chemical Reactions:

1. Dissolution of bauxite in NaOH:

$$ Al_2O_3 + 2NaOH + 3H_2O \rightarrow 2Na[Al(OH)_4] $$

2. Precipitation of aluminium hydroxide:

$$ 2Na[Al(OH)_4] + CO_2 \rightarrow 2Al(OH)_3 \downarrow + Na_2CO_3 $$

3. Formation of alumina by heating:

$$ 2Al(OH)_3 \rightarrow Al_2O_3 + 3H_2O $$

In this process, impurities like iron oxide and silica remain undissolved and are removed as waste.

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Solution 2: Simple and Understandable Answer

Hall’s process is used to purify aluminium ore. The main goal is to remove unwanted materials and get pure alumina.

Steps:

• Bauxite is mixed with a special liquid (NaOH) to dissolve aluminium compounds.
• A gas (CO₂) is added to get aluminium hydroxide.
• This is heated to remove water, leaving behind alumina (Al₂O₃).

Example: Just like boiling water removes impurities, heating aluminium hydroxide gives us pure alumina.

Exercises | Q 10.4 | Page 109

Complete the statement using every given option:

During the extraction of aluminium... Heating the aluminium ore with concentrated caustic soda.

Solution 1: Scientific and Written Exam Answer

When bauxite (Al₂O₃·xH₂O) is heated with concentrated sodium hydroxide (NaOH), aluminium oxide dissolves, forming soluble sodium aluminate (Na[Al(OH)₄]).

Chemical Reaction:

$$ Al_2O_3 + 2NaOH + 3H_2O \rightarrow 2Na[Al(OH)_4] $$

The impurities like iron oxide (Fe₂O₃) and silica (SiO₂) remain undissolved and are removed by filtration. This process is also known as the **Bayer’s Process**.

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Solution 2: Simple and Understandable Answer

Bauxite is a rock that contains aluminium. To extract aluminium, we mix it with a strong liquid (NaOH). This makes the useful aluminium part dissolve, while the unwanted dirt stays behind.

Steps:

• The ore is mixed with caustic soda (NaOH) and heated.
• Aluminium dissolves, forming sodium aluminate.
• Unwanted materials like iron oxide and sand are removed.

Example: Like dissolving sugar in water, aluminium dissolves in caustic soda, leaving dirt behind.

Exercises | Q 10.4 | Page 109

Complete the statement using every given option:

During the extraction of aluminium... Heating the aluminium ore with concentrated caustic soda.

Solution 1: Scientific and Written Exam Answer

When bauxite (Al₂O₃·xH₂O) is heated with concentrated sodium hydroxide (NaOH), aluminium oxide dissolves, forming soluble sodium aluminate (Na[Al(OH)₄]).

Chemical Reaction:

$$ Al_2O_3 + 2NaOH + 3H_2O \rightarrow 2Na[Al(OH)_4] $$

The impurities like iron oxide (Fe₂O₃) and silica (SiO₂) remain undissolved and are removed by filtration. This process is also known as the **Bayer’s Process**.

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Solution 2: Simple and Understandable Answer

Bauxite is a rock that contains aluminium. To extract aluminium, we mix it with a strong liquid (NaOH). This makes the useful aluminium part dissolve, while the unwanted dirt stays behind.

Steps:

• The ore is mixed with caustic soda (NaOH) and heated.
• Aluminium dissolves, forming sodium aluminate.
• Unwanted materials like iron oxide and sand are removed.

Example: Like dissolving sugar in water, aluminium dissolves in caustic soda, leaving dirt behind.

Class 10 Science Solutions

Chapter-Wise Solutions
CH:1 Gravitation Class 10th Solutions
CH:2 Periodic Classification of Elements Class 10th Solutions
CH:3 Chemical Reactions and Equations Class 10th Solutions
CH:4 Effects of Electric Current Class 10th Solutions
CH:5 Heat Class 10th Solutions
CH:6 Refraction of Light Class 10th Solutions
CH:7 Lenses Class 10th Solutions
CH:8 Metallurgy Class 10th Solutions
CH:9 Carbon Compounds Class 10th Solutions
CH:10 Space Missions Class 10th Solutions