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Difficulty: MediumSeparating Funnel and Solvent Extraction

An aqueous mixture containing a dissolved organic compound is shaken with trichloromethane (CHCl3\text{CHCl}_3) in a separating funnel and left to settle into two distinct phases. Given that trichloromethane has a density of 1.49 g/cm31.49\text{ g/cm}^3 and water has a density of 1.00 g/cm31.00\text{ g/cm}^3, which layer is drained out first from the stopcock at the bottom of the funnel?

  1. The trichloromethane layer at the bottom, because it is denser than waterAnswer
  2. B
    The aqueous layer at the bottom, because water has a lower density than trichloromethane
  3. C
    The trichloromethane layer at the top, because organic solvents always float above aqueous solutions
  4. D
    Neither layer, because trichloromethane and water mix completely to form a single homogeneous solution

Answer

The trichloromethane layer at the bottom, because it is denser than water
In a separating funnel containing two immiscible liquids, the denser liquid forms the lower layer and the less dense liquid forms the upper layer. Since trichloromethane (1.49 g/cm31.49\text{ g/cm}^3) is denser than water (1.00 g/cm31.00\text{ g/cm}^3), it resides at the bottom and is drained out first when the stopcock is opened.

Step-by-Step Solution

1
Compare the densities of the two immiscible liquids
Trichloromethane density (1.49 g/cm31.49\text{ g/cm}^3) > Water density (1.00 g/cm31.00\text{ g/cm}^3)
The liquid with the higher density will sink to the bottom phase of the separating funnel.
2
Determine layer placement in the separating funnel
Trichloromethane forms the bottom layer; water forms the top layer.
Immiscible liquids arrange according to relative density.
3
Identify which layer is drained out first
Opening the stopcock at the bottom drains the lower (trichloromethane) layer first.
The stopcock is located at the bottom of the funnel, so the denser bottom liquid discharges first.

Key Concept

Separating Funnel and Layer Placement by Relative Density
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Topics

Separating Funnel and Solvent Extraction

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