Is it always apparent in a solution which component is the solute, for example, in a solution of liquid in a liquid?

No, it is not always apparent, especially when the two components are miscible. Nitrogen in Oxygen gas is an example , as is kerosene in gasoline.

In a solution of liquid in a liquid, determining which component is the solute may not always be apparent solely based on observation. However, there are a few methods to determine the solute in a liquid-liquid solution:

1. Literature or Reference Sources: Consult literature or reference sources such as textbooks, research papers, or reliable online sources to identify the solute component of a specific liquid-liquid solution. These sources usually provide information on the composition and properties of solutions.

2. Solubility Data: If you have access to solubility data, it can help identify the solute. Solubility data typically indicates the maximum amount of solute that can dissolve in a solvent at a specific temperature. By comparing the observed concentrations of the two liquids and their solubility values, you can determine which component is in excess and thereby identify the solute.

3. Density Measurements: Density can sometimes help identify the solute in a liquid-liquid solution. By measuring the density of the solution and comparing it to the densities of the pure liquids, you can infer which component is the solute. The solute usually has a lower density when it dissolves in a solvent.

4. Distillation: Distillation is a separation technique that utilizes differences in boiling points. If the boiling points of the two liquids in a solution (solute and solvent) are significantly different, distillation can help separate the components. By collecting the distillate, you can identify the low boiling point component, indicating that it was the solute.

It is important to note that these are general methods and may require specific conditions or additional techniques for accurate identification of the solute in specific liquid-liquid solutions.