Final answer:
To determine which layer is aqueous in a separatory funnel, we can add a few drops of water and observe which layer they join. For separating butyric acid from hexane, liquid-liquid extraction is used, exploiting their solubility in water versus an organic layer. Alternatively, distillation utilizes differences in their boiling points to achieve separation.
Step-by-step explanation:
To determine which layer in a separatory funnel is the aqueous layer, you could add a few drops of water to the funnel and observe which layer the added water joins. Water will integrate into the aqueous layer due to its polarity and miscibility with other aqueous substances. Regarding the separation of butyric acid and hexane, we would employ the method of liquid-liquid extraction. Butyric acid is more soluble in water due to being a carboxylic acid (can form hydrogen bonds with water), while hexane, a hydrocarbon, is non-polar and will not mix with water.
After adding an aqueous solution to the funnel, the butyric acid would preferentially dissolve in the aqueous layer, while the hexane would remain in the organic layer. By draining the bottom layer, you could separate butyric acid from hexane if it formed the bottom layer, or remove the top layer if the hexane formed it. This separation technique is based on different partitioning behaviors of compounds in immiscible liquids.
If the distillation method is chosen, because hexane and butyric acid have different boiling points, hexane being the more volatile would vaporize first, and could then be condensed and collected, effectively separating it from the less volatile butyric acid.