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NEET • CHEMISTRY • GENERAL PRINCIPLES AND PROCESSES OF ISOLATION OF ELEMENTS

General principles and processes of isolation of elements practice · Easy

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61 Easy

61 of 69Question permalink

Remembering +4 | -1

In electrolysis of aluminium oxide which of the following is added to accelerate the process

View answer and explanation

Correct option: C

Cryolite

Option C (Cryolite) is correct because cryolite lowers the melting point of alumina and increases its conductivity, accelerating the electrolysis process.

Solution approach

Correct Answer + Core Reason: Cryolite is added to accelerate the electrolysis of aluminum oxide by lowering the melting point and increasing conductivity.

Step-by-Step Solution:

Step 1: Understand the process of aluminum extraction. Aluminum is extracted from its ore, bauxite (Al2O3), through electrolysis.

Step 2: Identify the problem with direct electrolysis. Aluminum oxide has a very high melting point (over 2000°C), making direct electrolysis energy-intensive and expensive.

Step 3: Explain the role of cryolite. Cryolite (Na3AlF6) is added to aluminum oxide to lower the melting point to around 950°C. This reduces energy consumption and makes the process more economical. Cryolite also increases the electrical conductivity of the electrolyte.

Step 4: Summarize the function. Cryolite acts as a solvent for alumina and improves the efficiency of the electrolytic process.

Why other options are wrong:
- Option A: Silica (SiO2) is a common impurity in bauxite but is not intentionally added to accelerate electrolysis. It does not significantly lower the melting point or increase conductivity.
- Option B: Silicate compounds are not used to accelerate the electrolysis of aluminum oxide. They do not have the properties required to improve the process.
- Option D: Nickel (Ni) is a metal and is not used in the electrolysis of aluminum oxide. It does not affect the melting point or conductivity of the electrolyte.

Key Concepts:
- Electrolysis
- Aluminum extraction (Hall-Héroult process)
- Properties of cryolite
- Melting point depression
- Electrical conductivity

Memory Aids:
- Cryolite = "C"onductivity and lower melting point for "Cryo"-electrolysis.

Quick Tips:
- Remember that cryolite is crucial for the efficient extraction of aluminum by electrolysis due to its ability to lower the melting point and increase conductivity.

62 Easy

62 of 69Question permalink

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Metals occur in the native form because of their:

View answer and explanation

Correct option: C

Low reactivity

Option C (Low reactivity) is correct because metals with low reactivity are less likely to form compounds and can exist in their elemental form.

Solution approach

Correct Answer + Core Reason: Metals occur in the native form because of their low reactivity.

Step-by-Step Solution:

Step 1: Metals that are highly reactive tend to form compounds with other elements (e.g., oxygen, sulfur) in the environment.

Step 2: Metals with low reactivity are less likely to react and can exist in their elemental or native form.

Step 3: Examples of metals that occur in the native form include gold (Au), platinum (Pt), and silver (Ag).

Why other options are wrong:
- Option A: High electronegativity indicates a strong tendency to attract electrons and form compounds.
- Option B: High reactivity means the metal readily reacts with other elements, preventing it from existing in the native form.
- Option D: Low density is not directly related to whether a metal occurs in the native form.

Key Concepts:
- Reactivity of metals
- Native state
- Electronegativity

Memory Aids:
- Low reactivity = Native state

Quick Tips:
- Remember that less reactive metals are more likely to be found in their native form.

63 Easy

63 of 69Question permalink

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The inner lining of a blast furnace is made up of:

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Correct option: C

Fire clay bricks

Option C (Fire clay bricks) is correct because fire clay bricks are used for the inner lining of a blast furnace due to their high-temperature resistance.

Solution approach

Correct Answer + Core Reason: Fire clay bricks. These bricks can withstand the high temperatures inside a blast furnace.

Step-by-Step Solution:

Step 1: Identify the requirement: The inner lining of a blast furnace needs to withstand extremely high temperatures.

Step 2: Consider the properties of different materials: Fire clay bricks are known for their refractory properties, meaning they can withstand high temperatures without melting or degrading.

Step 3: Conclusion: Therefore, fire clay bricks are used for the inner lining.

Why other options are wrong:
- Option A: Graphite bricks are used in some high-temperature applications, but not typically as the primary lining of a blast furnace due to their cost and other properties.
- Option B: Silica bricks are also refractory but less resistant to thermal shock than fire clay bricks, making them less suitable for the blast furnace environment.
- Option D: Basic bricks are used in certain metallurgical processes, but fire clay bricks are more common and suitable for the overall lining of a blast furnace.

Key Concepts:
- Metallurgy
- Blast furnace
- Refractory materials
- Fire clay bricks

Memory Aids:
- Think of \"fire\" and \"clay\" being resistant to heat.

Quick Tips:
- Remember that blast furnaces operate at extremely high temperatures, so the lining must be made of a material that can withstand those temperatures.

64 Easy

64 of 69Question permalink

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A carbonate ore is

View answer and explanation

Correct option: C

Siderite

Option C (Siderite) is correct because Siderite (

FeCO_3

) is a carbonate ore.

Solution approach

Correct Answer + Core Reason: Siderite. Siderite is a carbonate ore of iron ( $FeCO_3$ ).

Step-by-Step Solution:

Step 1: Define carbonate ore: A carbonate ore contains a metal combined with the carbonate anion ( $CO_3^{2-}$ ).

Step 2: Consider Carnallite: Carnallite is a chloride ore ( $KCl.MgCl_2.6H_2O$ ).

Step 3: Consider Limonite: Limonite is a hydrated iron oxide ore ( $Fe_2O_3.nH_2O$ ).

Step 4: Consider Siderite: Siderite is iron(II) carbonate ( $FeCO_3$ ), a carbonate ore.

Step 5: Consider Horn silver: Horn silver is silver chloride ( $AgCl$ ), a halide ore.

Why other options are wrong:
- Option A: Carnallite is a chloride ore, not a carbonate ore.
- Option B: Limonite is a hydrated oxide ore, not a carbonate ore.
- Option D: Horn silver is a chloride ore, not a carbonate ore.

Key Concepts:
- Carbonate Ores
- Ore Types (Oxide, Sulfide, Halide, Carbonate)

Memory Aids:
- Siderite: Iron Carbonate ( $FeCO_3$ )

Quick Tips:
- Memorize common ore formulas and their classifications.
- Recognize the carbonate anion ( $CO_3^{2-}$ ) in carbonate ores.

65 Easy

65 of 69Question permalink

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Pig iron:

View answer and explanation

Correct option: A

Contains carbon and other impurities

Option A (Contains carbon and other impurities) is correct because pig iron is the crude iron obtained from a blast furnace and contains a high percentage of carbon and other impurities.

Solution approach

Correct Answer + Core Reason: Contains carbon and other impurities. Pig iron is the crude iron from a blast furnace and contains impurities.

Step-by-Step Solution:

Step 1: Define pig iron.

Step 2: Pig iron is the product obtained from the blast furnace during iron extraction.

Step 3: Consider the composition of pig iron. It contains a high percentage of carbon (around 4%) and other impurities like silicon, manganese, phosphorus, and sulfur.

Step 4: Pig iron is brittle and cannot be directly used for many applications.

Step 5: Conclude that pig iron contains carbon and other impurities.

Why other options are wrong:
- Option B: Is pure form of iron is incorrect. Pig iron is not pure; it contains many impurities.
- Option C: Is same as wrought iron is incorrect. Wrought iron is a purer form of iron with very low carbon content.
- Option D: Is same as steel is incorrect. Steel has a lower carbon content than pig iron and is produced by refining pig iron.

Key Concepts:
- Pig iron composition.
- Iron extraction process.
- Comparison with wrought iron and steel.

Memory Aids:
- Pig iron is crude and impure.

Quick Tips:
- Remember the different forms of iron and their carbon content.

66 Easy

66 of 69Question permalink

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The ore magnesite is:

View answer and explanation

Correct option: D

\mathrm{MgC}{\mathrm{O}_3}

Option D (

\mathrm{MgC}{\mathrm{O}_3}

) is correct because magnesite is the mineral form of magnesium carbonate.

Solution approach

Correct Answer + Core Reason: $\mathrm{MgC}{\mathrm{O}_3}$ . Magnesite is magnesium carbonate.

Step-by-Step Solution:

Step 1: Recall the chemical formula of magnesite: Magnesite is a mineral composed of magnesium carbonate.

Step 2: Identify the correct formula: The chemical formula for magnesite is $\mathrm{MgC}{\mathrm{O}_3}$ .

Step 3: Evaluate the other options: The other options represent different minerals or compounds.

Step 4: Conclusion: $\mathrm{MgC}{\mathrm{O}_3}$ is the correct answer.

Why other options are wrong:
- **Option A ( $\mathrm{MgC}{\mathrm{O}_3} \cdot \mathrm{CaC}{\mathrm{O}_3}$ ): This is dolomite, not magnesite.
- Option B ( $\mathrm{MgC}{\mathrm{l}_2} \cdot \mathrm{KCl} \cdot 6{\mathrm{H}_2}\mathrm{O}$ ): This is carnallite, not magnesite.
- Option C ( $\mathrm{MgS}{\mathrm{O}_4} \cdot 7{\mathrm{H}_2}\mathrm{O}$ ): This is epsomite, not magnesite.

Key Concepts:
- Mineralogy
- Ore identification
- Chemical formulas of minerals

Memory Aids:
- Magnesite = Magnesium Carbonate

Quick Tips:**
- Memorize the chemical formulas of common ores and minerals.

67 Easy

67 of 69Question permalink

Understanding +4 | -1

Observe the following statements regarding purification of bauxite

I.During Hall’s process, silica is removed as Si (vapour).

II. Bauxite ore contaminated with

\mathrm{F}{\mathrm{e}_2}{\mathrm{O}_3}

is purified in Baeyer’s process.

III.During Serpeck’s process, AlN is formed.

The correct answer is

View answer and explanation

Correct option: D

Only II and III are correct

Option D (Only II and III are correct) is correct because statements II and III are true regarding the purification of bauxite.

Solution approach

Correct Answer + Core Reason: Only statements II and III are correct.

Step-by-Step Solution:

Step 1: Analyze each statement:
- I: During Hall’s process, silica is not removed as Si (vapor). Hall's process is primarily for the electrolysis of alumina.
- II: Bauxite ore contaminated with $Fe_2O_3$ is purified in Baeyer’s process. This is correct; Baeyer's process uses NaOH to dissolve alumina, leaving $Fe_2O_3$ as a solid impurity.
- III: During Serpeck’s process, AlN is formed. This is correct; Serpeck's process involves heating bauxite with coke and nitrogen to form aluminum nitride (AlN).

Step 2: Determine the correct statements based on the analysis.

Why other options are wrong:
- Option A: I, II and III are correct - Incorrect because statement I is wrong.
- Option B: Only I and II are correct - Incorrect because statement I is wrong.
- Option C: Only I and III are correct - Incorrect because statement I is wrong.

Key Concepts:
- Purification of bauxite
- Hall's process
- Baeyer's process
- Serpeck's process

Memory Aids:
- Baeyer's: Bauxite + NaOH
- Serpeck's: AlN formation

Quick Tips:
- Remember the specific processes used for bauxite purification and the reactions involved.

68 Easy

68 of 69Question permalink

Remembering +4 | -1

Purification of alumina takes place by

View answer and explanation

Correct option: B

Hall’s process

Option B (Hall’s process) is correct because Hall's process is used for the electrolytic reduction of alumina (Al2O3) to obtain aluminum.

Solution approach

Correct Answer + Core Reason: Hall’s process. Hall’s process is used for the electrolytic reduction of alumina.

Step-by-Step Solution:

Step 1: Recall the methods for purifying alumina.

Step 2: Hall's process involves dissolving alumina (Al2O3) in molten cryolite (Na3AlF6) and electrolyzing the mixture.

Step 3: This process is used to obtain pure aluminum.

Why other options are wrong:
- Option A: Bosch process is incorrect. The Bosch process is used for the production of hydrogen.
- Option C: Hoope’s process is incorrect. Hoope's process is used for the purification of aluminum, not alumina.
- Option D: Quartation process is incorrect. The Quartation process is a method for separating gold from silver.

Key Concepts:
- Hall's process.
- Alumina purification.
- Electrolytic reduction.

Memory Aids:
- Hall's process is for Alumina.

Quick Tips:
- Remember the specific processes associated with particular metals and their ores.

69 Easy

69 of 69Question permalink

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Hoope’s process is used for the purification of the metal

View answer and explanation

Correct option: B

Option B (Al) is correct because Hoope's process is an electrolytic refining method specifically used for the purification of aluminum.

Solution approach

Correct Answer + Core Reason: Al. Hoope’s process is used for the purification of Aluminum.

Step-by-Step Solution:

Step 1: Recall the different methods for metal purification.

Step 2: Hoope's process is an electrolytic refining method.

Step 3: Hoope's process is specifically designed for the purification of aluminum.

Step 4: The process involves three liquid layers with different densities and compositions, with electrolysis occurring between them.

Why other options are wrong:
- Option A: Cu is incorrect. Copper purification often involves electrolytic refining, but not Hoope's process specifically.
- Option C: Zn is incorrect. Zinc purification involves other methods like fractional distillation.
- Option D: Ag is incorrect. Silver purification involves methods like the Parkes process or electrolytic refining, but not Hoope's process.

Key Concepts:
- Hoope's process.
- Aluminum purification.
- Electrolytic refining.

Memory Aids:
- Hoope's = Aluminum purification.

Quick Tips:
- Remember the specific purification methods associated with particular metals.

Revision notes and key takeaways

Review GENERAL PRINCIPLES AND PROCESSES OF ISOLATION OF ELEMENTS in your textbook or class notes, then use this set to check your understanding.

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