Final answer:
Hexane has the lowest solubility in water among the compounds listed because it is a nonpolar substance and does not interact well with the polar solvent water. The correct answer is a. hexane.
Step-by-step explanation:
The solubility of a compound in water is influenced by the polarity of the compound in relation to water. Water is a polar solvent, which means that substances with similar polarities are more likely to be soluble in water.
The compound with the lowest solubility in water from the given options is hexane (a). Hexane is a nonpolar hydrocarbon with no affinity for polar solvents like water. Therefore, it does not dissolve well in water.
In contrast, acetone and ethyl alcohol (ethanol) have polar groups that can form hydrogen bonds with water, making them highly soluble.
Sugar, which is also polar, dissolves well in water due to its ability to form multiple hydrogen bonds. Methanol is highly soluble in water just like ethanol because it contains a polar hydroxyl (-OH) group capable of hydrogen bonding.