Identify the compound in each group that is most soluble in water. Explain.
b. pentane, 1-hexanol, propanoic acid

Verified step by step guidance

1. Step 1: Understand the concept of solubility in water. Water is a polar solvent, meaning it dissolves polar compounds and ionic substances well due to its ability to form hydrogen bonds. Nonpolar compounds, on the other hand, are less soluble in water.
2. Step 2: Analyze the molecular structure of each compound. Pentane is a hydrocarbon with no polar functional groups, making it nonpolar. 1-Hexanol contains a hydroxyl (-OH) group, which is polar and can form hydrogen bonds with water. Propanoic acid contains a carboxylic acid (-COOH) group, which is highly polar and can form strong hydrogen bonds with water.
3. Step 3: Compare the polarity and ability to form hydrogen bonds for each compound. Pentane, being nonpolar, will have the lowest solubility in water. 1-Hexanol, with its polar hydroxyl group, will have moderate solubility. Propanoic acid, with its highly polar carboxylic acid group, will have the highest solubility in water.
4. Step 4: Consider the size of the molecules. Larger nonpolar regions in a molecule can reduce solubility in water. Pentane has a purely nonpolar structure, while 1-Hexanol has a larger nonpolar region compared to propanoic acid, which is smaller and more polar overall.
5. Step 5: Conclude that propanoic acid is the most soluble in water due to its highly polar carboxylic acid group, followed by 1-Hexanol with its polar hydroxyl group, and pentane being the least soluble due to its nonpolar nature.

Key Concepts

Polarity

Polarity refers to the distribution of electrical charge over the atoms in a molecule. Polar molecules, which have a significant difference in electronegativity between their atoms, tend to dissolve well in water due to hydrogen bonding. In contrast, nonpolar molecules do not interact favorably with water, making them less soluble.

Hydrogen Bonding

Hydrogen bonding is a type of strong dipole-dipole attraction that occurs between molecules when hydrogen is bonded to highly electronegative atoms like oxygen or nitrogen. This interaction significantly increases the solubility of compounds in water, as seen in alcohols and carboxylic acids, which can form hydrogen bonds with water molecules.

Functional Groups

Functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. In the context of solubility, functional groups such as hydroxyl (-OH) in alcohols and carboxyl (-COOH) in acids enhance water solubility due to their ability to form hydrogen bonds, while hydrocarbon chains, like those in pentane, are hydrophobic and reduce solubility.