Chemistry
10th Edition
ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Chapter1: Chemical Foundations
Section: Chapter Questions
Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...
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Transcribed Image Text:**Instructions: TLC Plate Analysis**
**Question 4:**
Using the Rf value of 0.9, draw the TLC plate and comment on the polarity of the molecule if the solvent is 50% Ethyl acetate/Hexanes.
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**Explanation:**
Rf (Retention factor) values in Thin Layer Chromatography (TLC) provide insight into the polarity of a compound relative to the solvent system. An Rf value of 0.9 indicates the molecule traveled 90% of the distance up the TLC plate.
**Procedure to Draw a TLC Plate:**
1. **Plate Preparation:**
- Draw a baseline near the bottom of the plate.
- Spot the sample on the baseline.
2. **Developing the Plate:**
- Place the plate in a chamber with the solvent mixture (50% Ethyl acetate and 50% Hexanes).
3. **Observations:**
- The sample's spot will move up the plate.
- Measure the distance the spot covers from the baseline.
- Calculate Rf (Rf = Distance traveled by compound / Distance traveled by solvent front).
**Comments on Polarity:**
- **Rf = 0.9:** This high Rf value suggests the compound is less polar, as it moves easily with the relatively less polar solvent mixture of Ethyl acetate/Hexanes.
- **Solvent System:** The 50% Ethyl acetate/Hexanes mixture is moderately polar, indicating that the compound is non-polar to weakly polar compared to the solvent system.
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Always remember, lower Rf values typically indicate higher polarity, as the compound interacts more with the stationary phase. In contrast, higher Rf values suggest lower polarity, with the compound preferentially interacting with the mobile phase.
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