Final answer:
Pure water has the highest water vapor pressure because it does not contain solutes that would lower its vapor pressure, unlike the other options which are solutions containing solute particles. option b is correct.
Step-by-step explanation:
The question concerns the vapor pressure of various solutions and aims to identify which of the given options has the highest water vapor pressure. In chemistry, the concept known as Raoult's Law explains that the vapor pressure of a solvent is lowered when a nonvolatile solute is dissolved in it. This is due to the fact that solute particles occupy space at the surface of the liquid and impede the evaporation of solvent molecules.
Given the options of a dilute saltwater solution, pure water, a sugar solution, and a concentrated saltwater solution, pure water (option a) would have the highest water vapor pressure. This is because pure water does not contain any solutes that would decrease its vapor pressure. In contrast, both dilute and concentrated saltwater solutions, as well as the sugar solution, will have lower vapor pressures due to the presence of solute particles that hinder the escape of water molecules into the vapor phase.
Therefore, the correct option, demonstrating the highest water vapor pressure, is pure water.