Final answer:
In a solution made of 15 mL of oxygen and 5 mL of helium, oxygen is the solvent and helium is the solute. This determination is based on the relative amounts of each substance, with the greater quantity being the solvent.
Step-by-step explanation:
To determine the solvent and solute in a solution, consider the quantities of the substances involved. Typically, the substance present in the greater amount is the solvent, and the substance present in the lesser amount is the solute. In the provided example where a solution is made of 15 mL of oxygen and 5 mL of helium, oxygen would be the solvent since there is more of it, and helium would be the solute.
Similarly, in the given reference exercise where 3.33 g of HCl(g) is dissolved in 40.0 g of liquid methyl alcohol (CH3OH), the methyl alcohol is the solvent due to its larger quantity, and the gaseous HCl is the solute.