Question 1

Does the partition coefficient have units?

Accepted Answer

No, $K_{pc}$ is a dimensionless quantity. It is a ratio of two concentrations measured in the same units (e.g., mol dm⁻³ / mol dm⁻³ or g cm⁻³ / g cm⁻³), so the units cancel out.

Question 2

What does a very large $K_{pc}$ value (e.g., 1000) tell you about a solute's properties?

Accepted Answer

A very large $K_{pc}$ means the solute is vastly more soluble in the numerator solvent than the denominator solvent. For example, if $K_{pc} = \frac{[X_{organic}]}{[X_{aqueous}]} = 1000$, it implies that compound X is highly non-polar or has features that make it much more stable in the organic solvent than in water.

Question 3

Why is a separating funnel the specific apparatus used for solvent extraction?

Accepted Answer

A separating funnel is designed for this purpose. Its shape allows for vigorous shaking to ensure equilibrium is reached. It has a stopper to prevent leakage during shaking and a tap at the bottom that allows the denser, lower layer to be carefully drained off, achieving a clean separation of the two immiscible liquids.

Question 4

Is partitioning related to chromatography?

Accepted Answer

Yes, absolutely. Partitioning is the fundamental principle behind many forms of chromatography, such as paper chromatography and gas-liquid chromatography (GLC). In these techniques, solutes continuously partition between a stationary phase and a mobile phase. Differences in the partition coefficients for different solutes cause them to move at different rates, leading to separation.

Partition coefficients

What you need to know

The Solvent Tug-of-War