Final answer:
Water and cyclohexane cannot be considered a solvent pair because water is a polar solvent while cyclohexane is nonpolar. They do not mix well together due to their differing intermolecular forces, following the 'like dissolves like' principle.
Step-by-step explanation:
When considering whether water and cyclohexane can be considered a solvent pair, it is essential to consider the polarity of the solvents. Water is a polar solvent, exhibiting strong hydrogen bonding, which makes it excellent for dissolving other polar substances. Cyclohexane, on the other hand, is a nonpolar solvent, which means it lacks the polar groups or electronegativity differences that would allow for hydrogen bonding and is instead stabilized by dispersion forces.
According to the principle of "like dissolves like," polar and nonpolar solvents do not mix well together. This is because the different types of intermolecular forces that polar and nonpolar substances experience do not lead to a negative enthalpy of solution that would allow them to dissolve in one another efficiently. In fact, water and cyclohexane are often used together in separations precisely because they do not dissolve in each other, which allows for differing solutes to partition into the layer which best matches their own polarity. Therefore, water and cyclohexane cannot be considered a soluble pair.
To illustrate, consider a polar molecule like methanol (CH3OH) and a nonpolar molecule like n-hexane (C6H14). Methanol would be more inclined to dissolve in water due to similar intermolecular forces (hydrogen bonding), while n-hexane would be more soluble in cyclohexane because both are nonpolar hydrocarbons driven by dispersion forces.