Subtopic: Fundamentals of Downstream processing (chromatography, filtration)
Question Statement:
In a thin layer chromatography experiment using a silica gel plate, a compound showed migration of
12.5 cm and the solvent front showed migration of 18 cm. The Re value for the compound is _
Official Answer Key:
0.68 to 0.70
Step-by-Step Solution & Explanation
### **Official Solution & Step-by-Step Derivation (GATE BT 2017 Q.5)**
**1. Governing Concept & Syllabus Classification**:
- **Section**: BT
- **Question Type**: **NAT** (1 Mark)
- **Core Topic**: Quantitative & Analytical Aptitude
**2. Detailed Step-by-Step Analytical & Scientific Derivation**:
- **Mathematical & Quantitative Formulation**:
- Problem Statement: *"In a thin layer chromatography experiment using a silica gel plate, a compound showed migration of
12.5 cm and the solvent front showed migration of 18 cm. The Re value for the compound is _..."*
- Identifying governing bioprocess / mathematical relation:
- Calculating retention/retardation factor ($R_f$) in planar chromatography:
$R_f = \frac{\text{Distance migrated by solute}}{\text{Distance migrated by solvent front}}$
- **Official Answer Key Interval**: Evaluated numerical range is **0.68 to 0.7** (Target value: **0.68 to 0.7**).
**3. Final Answer / Verification Summary**:
- **Official GATE Answer Key**: **0.68 to 0.7**
- **Scoring Criteria**: 1 Mark (Negative marking: -0.0 marks).
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