The Question is from neet-chemistry basic-chemistry-concepts concentration-methods, and it was created by the author Mr. S M HUSSAIN

Question

In the leaching of alumina from bauxite, the concentration of the ore is achieved by:

Mr. S M HUSSAIN · Accepted Answer

## CORE INFORMATION
✓ **Answer**: A
## CONCEPT FRAMEWORK
 **Primary Concept**: Hydrometallurgy and Alumina Extraction
 **Related Topics**: Bauxite, Bayer process, leaching, concentration
 **Prerequisites**: Basic understanding of chemical reactions and separation techniques.
## SOLUTION PATHWAY
**Given Information**:
The question asks about the method used to concentrate alumina during its extraction from bauxite.
**Method & Steps**:
1. Understanding the Bayer process:
  Reasoning: The Bayer process is the primary industrial method for alumina ($Al_2O_3$) extraction from bauxite.  It involves several steps, including digestion (leaching), precipitation, and calcination.
  Formula/Rule:  No specific formula is directly applicable here, but understanding the chemical reactions involved is crucial. The key reaction in leaching is the dissolution of alumina in a sodium hydroxide solution.
2. Analyzing the concentration step:
  Working: During the Bayer process, bauxite is digested in a hot, concentrated sodium hydroxide solution.  This selectively dissolves the alumina, leaving behind impurities like iron oxides and silica.  The resulting solution is then concentrated, and the alumina is later precipitated as aluminum hydroxide.
  Key Point: The concentration step is not achieved through physical separation methods like froth flotation or magnetic separation.  It's achieved by selectively dissolving the desired component (alumina) and leaving behind the impurities.
3. Identifying the correct method:
  Result: Selective dissolution of alumina is the method used to concentrate the ore in the leaching process.
  Verification: The Bayer process relies on the difference in solubility between alumina and other components in bauxite. This selective dissolution is the basis for the concentration step.
 ## OPTION ANALYSIS
A ✓: Selective dissolution of alumina: This is the correct answer. The Bayer process uses a sodium hydroxide solution to selectively dissolve alumina from bauxite, concentrating it in the solution.
B :x: Froth flotation: This is a physical separation method used for separating minerals based on their hydrophobicity. It's not applicable to the selective dissolution of alumina.
C :x: Magnetic separation: This method separates materials based on their magnetic properties. Alumina is not magnetically separable from the impurities in bauxite.
D :x: Electrolysis: Electrolysis is used in the later stages of aluminum production to extract aluminum metal from alumina. It's not a concentration method for the ore.
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing leaching with other separation techniques: Students might mistakenly choose froth flotation or magnetic separation, failing to understand the chemical nature of the leaching process.
   How to avoid: Focus on understanding the chemical reactions involved in the Bayer process and the principle of selective dissolution.
  2.Overlooking the importance of selective dissolution:  Students might not fully grasp that the concentration is a consequence of the selective solubility of alumina in the alkaline solution.
   How to avoid: Carefully study the chemical reactions and the solubility properties of alumina and other components of bauxite.
 **Quick Tips**:
  1.Remember the Bayer process is the key to understanding alumina extraction and concentration.
  2.Focus on the selective dissolution aspect of the leaching step.

Mr. S M HUSSAIN · Answer

The correct Option is "Selective dissolution of alumina"

Mr. S M HUSSAIN · Answer

Froth flotation

Mr. S M HUSSAIN · Answer

Magnetic separation

Mr. S M HUSSAIN · Answer

Electrolysis

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