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Difficulty: MediumSeparating Funnel and Solvent Extraction

An aqueous solution of iodine is shaken with tetrachloromethane (CCl4CCl_4) in a separating funnel and allowed to settle. Given that tetrachloromethane is denser than water (1.59 g/cm31.59\text{ g/cm}^3 vs 1.00 g/cm31.00\text{ g/cm}^3), which of the following observations is correct?

  1. Two layers form, and iodine extracts preferentially into the lower CCl4CCl_4 layer.Answer
  2. B
    Two layers form, and iodine extracts preferentially into the upper CCl4CCl_4 layer.
  3. C
    A single homogeneous liquid layer forms because boiling point differences determine layer formation.
  4. D
    Iodine remains in the upper aqueous layer because CCl4CCl_4 distills off before solvent extraction occurs.

Answer

Two layers form, and iodine extracts preferentially into the lower CCl4CCl_4 layer.
Tetrachloromethane (CCl4CCl_4) is immiscible with water and has a higher density (1.59 g/cm31.59\text{ g/cm}^3) than water (1.00 g/cm31.00\text{ g/cm}^3), meaning it forms the lower layer in the separating funnel. Because non-polar iodine is far more soluble in non-polar CCl4CCl_4 than in water, it extracts into the bottom CCl4CCl_4 layer.

Step-by-Step Solution

1
Determine phase separation and relative layer positioning
Water and CCl4CCl_4 are immiscible liquids. Since CCl4CCl_4 has a higher density (1.59 g/cm31.59\text{ g/cm}^3) than water (1.00 g/cm31.00\text{ g/cm}^3), CCl4CCl_4 settles at the bottom while water forms the top layer.
Immiscible liquids separate into distinct layers according to their relative densities.
2
Analyze solute partitioning between the two phases
Iodine (I2I_2) is a non-polar molecule, making it significantly more soluble in the non-polar solvent CCl4CCl_4 than in polar water.
Solutes preferentially partition into the solvent in which they are more soluble (like dissolves like).
3
Combine observations to identify the correct outcome
Iodine transfers out of the aqueous phase into the lower CCl4CCl_4 layer.
Solvent extraction separates solutes based on differential solubility in immiscible liquid layers.

Key Concept

Solvent extraction depends on liquid-liquid immiscibility, density difference for layer positioning, and preferential solubility of the solute.
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Topics

Separating Funnel and Solvent Extraction

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