In an organic chemistry lab, why is the organic layer usually the upper layer in the separatory funnel while the aqueous layer is usually the bottom layer?
The density of H2O is about 1.00 g/mL. Many organic solvents have a density less than that; hence they float.
In an organic chemistry lab, when performing liquid-liquid extractions using a separatory funnel, the organic layer is typically the upper layer, while the aqueous layer is usually the bottom layer. This arrangement is observed due to differences in the densities of the organic and aqueous solutions.
The separation of the layers is based on the principles of immiscibility and density. Immiscibility refers to the inability of two liquids to dissolve in each other; in this case, the organic and aqueous solutions do not mix completely. When two immiscible liquids are combined, they tend to form separate layers due to differences in their densities.
Organic solvents generally have lower densities compared to water (which makes up the aqueous layer), resulting in the organic layer floating on top. Organic solvents are typically less dense because they are composed of carbon and hydrogen, which are lighter elements compared to oxygen and hydrogen found in water.
Thus, the organic layer becomes the upper layer while the aqueous layer becomes the bottom layer when the two immiscible liquids are settled in a separatory funnel. This enables easy separation and extraction of the desired organic compound from the aqueous solution during the extraction process.