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General Principles and Processes of Isolation of Elements WBCHSE Class 12 MCQ & Practice Questions

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General Principles and Processes of Isolation of Elements Revision Guide for WBCHSE Class 12 Chemistry

General Principles and Processes of Isolation of Elements is part of WBCHSE Class 12 Chemistry preparation. A strong revision plan should combine concept review with exam-style questions so that definitions, relationships, calculations and exceptions are recalled accurately.

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Top 20 General Principles and Processes of Isolation of Elements MCQs with Answers

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WBCHSE Class 12 Chemistry · General Principles and Processes of Isolation of Elements · Very Hard

1. The unwanted earthy impurities associated with an ore are called:

  • A. Slag
  • B. Matte
  • C. Gangue
  • D. Flux
Answer: C
Explanation: Gangue consists of unwanted earthy or rocky impurities present with an ore.

WBCHSE Class 12 Chemistry · General Principles and Processes of Isolation of Elements · Very Hard

2. Concentration of an ore means:

  • A. Electrorefining
  • B. Removal of gangue
  • C. Conversion of oxide to metal
  • D. Alloy formation
Answer: B
Explanation: Ore concentration enriches the desired mineral by removing gangue.

WBCHSE Class 12 Chemistry · General Principles and Processes of Isolation of Elements · Very Hard

3. Hydraulic washing separates ore and gangue mainly on the basis of difference in:

  • A. Densities
  • B. Magnetic properties
  • C. Boiling points
  • D. Acid strengths
Answer: A
Explanation: Gravity separation uses differences in specific gravity.

WBCHSE Class 12 Chemistry · General Principles and Processes of Isolation of Elements · Very Hard

4. Magnetic separation is useful when:

  • A. Both have identical magnetism
  • B. Ore is always soluble in water
  • C. Only gases are present
  • D. Ore and gangue differ in magnetic properties
Answer: D
Explanation: A magnetic separator exploits differing magnetic behaviour.

WBCHSE Class 12 Chemistry · General Principles and Processes of Isolation of Elements · Very Hard

5. Froth flotation is mainly used for concentration of:

  • A. Carbonate ores only
  • B. Native metals only
  • C. Sulphide ores
  • D. Oxide ores only
Answer: C
Explanation: Sulphide particles are preferentially wetted by oil and rise with froth.

WBCHSE Class 12 Chemistry · General Principles and Processes of Isolation of Elements · Very Hard

6. In froth flotation, pine oil commonly acts as a:

  • A. Reducing agent
  • B. Frother
  • C. Depressant
  • D. Flux
Answer: B
Explanation: Frothers stabilise the froth carrying ore particles.

WBCHSE Class 12 Chemistry · General Principles and Processes of Isolation of Elements · Very Hard

7. A depressant in froth flotation is used to:

  • A. Prevent one sulphide from entering the froth
  • B. Increase melting point of slag
  • C. Reduce metal oxide
  • D. Oxidise all sulphides
Answer: A
Explanation: Depressants selectively suppress flotation of a particular sulphide.

WBCHSE Class 12 Chemistry · General Principles and Processes of Isolation of Elements · Very Hard

8. Leaching involves:

  • A. Heating ore without air
  • B. Heating ore in excess air
  • C. Electrolysis of molten metal
  • D. Selective dissolution of the ore in a suitable reagent
Answer: D
Explanation: Leaching transfers the desired component into solution selectively.

WBCHSE Class 12 Chemistry · General Principles and Processes of Isolation of Elements · Very Hard

9. Bauxite is purified industrially by leaching with:

  • A. Dilute HCl only
  • B. NH4Cl
  • C. NaOH solution
  • D. NaCl solution
Answer: C
Explanation: Alumina dissolves in hot concentrated alkali as aluminate species.

WBCHSE Class 12 Chemistry · General Principles and Processes of Isolation of Elements · Very Hard

10. Gold and silver ores may be leached using:

  • A. Molten silica
  • B. Cyanide solution
  • C. Concentrated NaCl only
  • D. Pure water
Answer: B
Explanation: Cyanide forms soluble complexes with Au and Ag under controlled conditions.

WBCHSE Class 12 Chemistry · General Principles and Processes of Isolation of Elements · Very Hard

11. Calcination generally means heating an ore:

  • A. In limited or no air
  • B. In excess air
  • C. Under water
  • D. Only below room temperature
Answer: A
Explanation: Calcination is commonly used for carbonate/hydrated ores in limited air.

WBCHSE Class 12 Chemistry · General Principles and Processes of Isolation of Elements · Very Hard

12. Roasting generally means heating an ore:

  • A. In complete absence of air
  • B. In liquid nitrogen
  • C. Only with water
  • D. In excess air or oxygen
Answer: D
Explanation: Roasting oxidises sulphide ores in excess air.

WBCHSE Class 12 Chemistry · General Principles and Processes of Isolation of Elements · Very Hard

13. Calcination of a carbonate ore generally produces:

  • A. Metal chloride and H2
  • B. Metal nitride
  • C. Metal oxide and CO2
  • D. Metal sulphide and O2
Answer: C
Explanation: Carbonates decompose on heating to oxides with carbon dioxide evolution.

WBCHSE Class 12 Chemistry · General Principles and Processes of Isolation of Elements · Very Hard

14. Roasting of a sulphide ore commonly converts it into:

  • A. Nitride
  • B. Oxide
  • C. Carbonate
  • D. Hydride
Answer: B
Explanation: Sulphides are often oxidised to oxides during roasting.

WBCHSE Class 12 Chemistry · General Principles and Processes of Isolation of Elements · Very Hard

15. A flux is added during smelting to:

  • A. React with gangue to form slag
  • B. Increase gangue content
  • C. Prevent reduction
  • D. Form ore concentrate
Answer: A
Explanation: Flux converts gangue into a fusible slag.

WBCHSE Class 12 Chemistry · General Principles and Processes of Isolation of Elements · Very Hard

16. Slag is generally formed by reaction between:

  • A. Metal and reducing agent only
  • B. Ore and collector
  • C. Metal and electrolyte
  • D. Flux and gangue
Answer: D
Explanation: The flux chemically combines with gangue to form slag.

WBCHSE Class 12 Chemistry · General Principles and Processes of Isolation of Elements · Very Hard

17. If gangue is acidic, the flux should generally be:

  • A. Neutral only
  • B. A noble gas
  • C. Basic
  • D. Acidic
Answer: C
Explanation: An acidic gangue is neutralised by a basic flux.

WBCHSE Class 12 Chemistry · General Principles and Processes of Isolation of Elements · Very Hard

18. Silica gangue can be removed using a basic flux such as:

  • A. SO2
  • B. CaO
  • C. SiO2
  • D. CO2
Answer: B
Explanation: CaO reacts with SiO2 to form calcium silicate slag.

WBCHSE Class 12 Chemistry · General Principles and Processes of Isolation of Elements · Very Hard

19. Reduction of a metal oxide by carbon is feasible when:

  • A. Carbon oxidation is thermodynamically more favourable
  • B. Metal is always above carbon regardless of temperature
  • C. ΔG is always positive
  • D. No CO/CO2 can form
Answer: A
Explanation: The reducing agent must have a greater affinity for oxygen under the chosen conditions.

WBCHSE Class 12 Chemistry · General Principles and Processes of Isolation of Elements · Very Hard

20. Ellingham diagrams plot standard Gibbs energy change for:

  • A. Density versus pressure
  • B. Electrode potential versus concentration
  • C. pH versus volume
  • D. Oxide formation versus temperature
Answer: D
Explanation: Ellingham diagrams compare temperature dependence of oxidation free energies.

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