Partition coefficients
| English | Chinese | Pinyin |
|---|---|---|
| solvent | 溶剂 | róng jì |
| solute | 溶质 | róng zhì |
| partition coefficient | 分配系数 | fēn pèi xì shù |
| non-polar | 非极性 | fēi jí xìng |
| polar | 极性 | jí xìng |
| immiscible | 不混溶 | bù hùn róng |
Splitting between two solvents 溶剂
- Shake a solute 溶质 with two solvents that don't mix — it spreads between them.
- The ratio of its concentrations is the partition coefficient 分配系数.
- Polarity decides which solvent it prefers.
Partition coefficient lab
Kpc = concentration organic / concentration aqueous
Change organic-layer concentration and see the partition ratio.
A partition coefficient describes how a solute distributes between two immiscible solvents.
It is the ratio of concentrations at equilibrium.
The partition coefficient
- It is constant at a fixed temperature.
- It only applies when the solute is in the same physical state in both solvents.
The partition coefficient is:
Kpc = [solute in solvent 1] / [solute in solvent 2], constant at a fixed temperature.
The partition coefficient applies only when the solute is:
Kpc is valid when the solute exists in the same physical state in each solvent.
Match each partition idea.
Each item links the term to its correct meaning.
Polarity decides
- The value depends on the polarity of the solute and each solvent.
- A non-polar 非极性 solute dissolves more in the non-polar 极性 solvent; a polar solute prefers the polar solvent.
Polarity decides the split: a non-polar solute favours the non-polar layer, a polar solute the water layer.
A non-polar solute will dissolve more in:
"Like dissolves like": a non-polar solute prefers the non-polar solvent; a polar solute the polar one.
The value of the partition coefficient depends on the polarity of the solute and solvents.
Polarity governs how the solute distributes, so it sets the partition coefficient.
Using a partition coefficient
- The solute distributes between two immiscible 不混溶 solvents in a fixed ratio at equilibrium.
- This underlies solvent extraction and chromatography.
You've got it
- $K_{\text{pc}} = \dfrac{[\text{solute in solvent 1}]}{[\text{solute in solvent 2}]}$ (constant at fixed temperature)
- it applies when the solute is in the same physical state in both solvents
- non-polar solute → non-polar solvent; polar solute → polar solvent