If Dichloromethane (DCM) and water $$H_2O$$ are used for differential extraction, which one of the following statements is correct?

We begin by recalling the principle of differential extraction. In this technique two immiscible liquids are shaken together so that a solute can distribute itself preferentially into one of the layers. For the liquids to separate properly inside the separating funnel, they must satisfy two conditions: they must be immiscible, and they must have different densities, because density decides which layer will settle at the bottom.

Now we examine the pair given in the question: dichloromethane (abbreviated as DCM, chemical formula $$CH_2Cl_2$$) and water $$H_2O$$. The first thing to note is that DCM is an organochlorine solvent, whereas water is a polar protic solvent. Because of their very different intermolecular forces, they do not mix appreciably; thus they are indeed immiscible. So options that claim miscibility or formation of a turbid/colloidal mixture can already be ruled out.

Next we must decide which of the two liquids will occupy the lower position in the separating funnel. This is governed by the density relation

$$\text{Density} = \frac{\text{Mass}}{\text{Volume}}$$

The literature values at room temperature are

$$\rho_{\text{DCM}} \approx 1.33\ \text{g\,cm}^{-3}$$

$$\rho_{H_2O} \approx 1.00\ \text{g\,cm}^{-3}$$

Since $$1.33\ \text{g\,cm}^{-3} > 1.00\ \text{g\,cm}^{-3}$$, dichloromethane is denser than water. According to the basic rule, the denser liquid settles at the bottom, while the less dense liquid forms the upper layer. Therefore DCM will form the lower layer and water will form the upper layer inside the separating funnel.

This description matches the statement in Option C: “DCM and $$H_2O$$ would stay as lower and upper layer respectively in the S.F.”

Hence, the correct answer is Option C.