Final answer:
To determine the aqueous layer, examine the densities of the liquids after they have settled; the layer with a density closest to water (1.00 g/mL) is likely the aqueous one. Comparison to known densities or data sheets can also assist in identification.
Step-by-step explanation:
To determine which layer is the aqueous layer in a chemical experiment, one commonly used property to consider is the density of the liquids involved. The aqueous layer is typically the layer that consists of water or is water-based, and since the density of water is 1.00 g/mL at room temperature, the layer closer to this density value is likely to be the aqueous one. If you have a mixture of two immiscible liquids, the one with a density less than 1.00 g/mL will float on top, while the denser liquid will form the bottom layer.
This can be observed without additional substances or equipment by simply looking at the two layers after they have settled. The densities of substances involved in the chemical process are often known or can be found in a material safety data sheet (MSDS) or a chemistry reference. By comparing the known density of one liquid to the observed results or using a density value from a reliable source, you can identify the aqueous layer.