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EEJ MAIN Chemistry QUESTION #7501
Question 1

When dichloromethane (DCM) and water (H$_2$O) are used together for differential extraction, which statement correctly describes their behaviour in a separating funnel?

  • DCM forms the lower layer and H$_2$O the upper layer✔️
  • DCM and H$_2$O form a turbid colloidal mixture
  • DCM forms the upper layer and H$_2$O the lower layer
  • DCM and H$_2$O are completely miscible
Correct Answer Explanation

In solvent extraction, liquids separate into layers based on density.

  • Density of DCM (CH$_2$Cl$_2$) $\approx 1.33\ \text{g/mL}$ — denser than water.
  • Density of water $\approx 1.00\ \text{g/mL}$.
  • DCM and water are immiscible — they do not dissolve in each other.

Since DCM is denser, it sinks to the bottom, and water stays on top. They separate cleanly — no colloidal mixture forms.