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Questions and Answers
What is the primary purpose of solvent extraction in the experiments conducted?
Which of the following is NOT a method of solvent extraction discussed in the experiments?
Which solvent was specifically mentioned for dissolving samples in Experiment 1?
In the context of solid-liquid extraction, which of the following is a correct example?
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What observation was likely expected after dissolving samples in both H2O and EtOH?
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What are emulsions primarily composed of?
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What condition is necessary for the extraction and solution solvent in solvent extraction?
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What is the role of detergents in an emulsion?
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What issue does 'salting out' address in solvent extraction?
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Which of the following is NOT a requirement for an extraction solvent?
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How can one visualize the interface when it cannot be seen due to dark layers?
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Which of the following solvents has a higher density based on the given data?
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What does the Beer-Lambert Law express?
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Why is a quartz cuvette preferred over other materials for measuring absorbance?
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What role does dark incubation play in pigment extraction?
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What is the order of solubility of salicylic acid from highest to lowest in various solvents?
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What unit is used to express molar absorptivity in the content?
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If a compound has an absorbance of 1.35 in a 10-mm cuvette, what might be inferred about its concentration?
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Among the solvents listed, which has the highest boiling point?
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Which solvent has a reported miscibility with water?
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What is the purpose of using acetone, methanol, and ethanol in pigment extraction?
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What effect does cohesive energy have on the solubility of salicylic acid?
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What information is conveyed by the unique wavelength (wv) of a compound's absorbance?
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How is pigment concentration determined after absorbance measurement?
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At what temperature is the solubility of salicylic acid least in water?
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What is the solubility of salicylic acid in carbon tetrachloride (CCl4) at 25°C?
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Which of the following statements about xylene is correct?
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What form does salicylic acid crystallize into after heating?
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What are the two general steps conducted in the microscale extraction process?
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What is the role of the solvents used in the extraction process?
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What type of mixtures are formed during the solvent extraction process?
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Which of the following solvents is typically used in extraction due to its low density?
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How are solutes like SA, BA, and sucrose characterized in the extraction process?
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What is typically determined after conducting the extraction process?
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Why is the density of extraction solvents important?
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What happens to the solutes after extraction in the process?
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Study Notes
Experiments Overview
- Experiment 1 focused on solvent extraction techniques.
- Experiment 2 examined pigment extraction methods.
Solvent Extraction
- Extraction Defined: Process of separating a substance from a mixture based on its different solubility in two immiscible liquids.
- Liquid-Liquid Extraction: Involves separating compounds dissolved in two different liquids, e.g., using dichloromethane (DCM) and water.
- Solid-Liquid Extraction: Involves extracting substances from solid matrices into liquids, e.g., coffee extraction with hot water.
Key Compounds Used
- Salicylic Acid (HOC₆H₄COOH)
- Benzoic Acid (C₆H₅COOH)
- Sucrose (C₁₂H₂₂O₁₁) splits into glucose and fructose upon hydrolysis.
Extraction Methodology
- Samples dissolved in a combination of water and ethanol (EtOH).
- Utilize ethyl acetate (EtAC) and DCM for separation.
- Monitoring extraction involves calculating % yield and distribution coefficients (Kp).
Observations in Extraction
- Aqueous and organic layers exhibit clear separation post-extraction.
- Two steps: mixing immiscible liquids and separating resulting layers.
Solubility Insights
- Solubility of salicylic acid decreases in this order: Ethanol > Ethyl Acetate > Carbon Tetrachloride > Xylene > Water.
- High boiling points and cohesive energies of solvents affect their solubility characteristics.
Density of Solvents
- Density impacts separation efficiency of organic extracts.
- Ethyl acetate has a lower density (0.90 g/mL) compared to DCM (1.33 g/mL).
Troubleshooting Extraction
- Emulsions may form, complicating separation. Strategies include “salting out” to enhance separation.
- Dark layers can obscure visual identification of interfaces; use of light or funnel tilting aids in clarity.
Considerations for Effective Extraction
- Immiscibility between extraction and solution solvents is crucial.
- Extraction solvent should possess a high distribution coefficient (Kp) to favor the target component.
- Ideal solvents should be easily separable, low in toxicity, and cost-effective.
Pigment Extraction
- Conducted using acetone, methanol, and ethanol for sample preparation.
- Absorbance measured via spectrophotometry; Beer-Lambert Law relates absorbance to concentration.
Key Calculation in Pigment Extraction
- Example provided for determining molar absorptivity from absorbance data.
- Absorbance (A) of 1.35 at 750 nm in a 10-mm cuvette requires application of the Beer-Lambert Law for calculations.
Pigment Measurement
- Spectrophotometer measures light intensity absorbed by solutions, crucial for assessing pigment concentrations.
Conclusion
- Vital techniques in extraction methods include proper solvent selection, solubility understanding, and analytical measurements to ensure efficient and accurate outcomes in both experiments.
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Description
This quiz focuses on the post-laboratory discussions of two experiments: solvent extraction and pigment extraction. You will define key concepts and examples related to liquid-liquid and solid-liquid extraction methods. Test your understanding of these fundamental chemistry techniques.
