Predict which substance in each pair has the highest viscosity. (a) Hexane 1CH3CH2CH2CH2CH2CH32 or 1-hexanol 1CH3CH2CH2CH2CH2CH2OH2

Verified step by step guidance

1. Identify the molecular structure of each substance: Hexane is a hydrocarbon with the formula \( \text{C}_6\text{H}_{14} \), while 1-hexanol is an alcohol with the formula \( \text{C}_6\text{H}_{13}\text{OH} \).
2. Consider the intermolecular forces present in each substance: Hexane, being a nonpolar molecule, primarily exhibits London dispersion forces. 1-hexanol, on the other hand, is capable of hydrogen bonding due to the presence of the hydroxyl (\( \text{OH} \)) group.
3. Understand that viscosity is influenced by the strength of intermolecular forces: Stronger intermolecular forces generally lead to higher viscosity because the molecules are more strongly attracted to each other, making it harder for them to flow past one another.
4. Compare the intermolecular forces: Since hydrogen bonding is stronger than London dispersion forces, 1-hexanol will have stronger intermolecular forces compared to hexane.
5. Predict the substance with the highest viscosity: Based on the stronger intermolecular forces due to hydrogen bonding, 1-hexanol is expected to have a higher viscosity than hexane.

Key Concepts

Viscosity

Viscosity is a measure of a fluid's resistance to flow. It reflects how easily molecules within a substance can move past one another. Higher viscosity indicates a thicker fluid that flows more slowly, while lower viscosity corresponds to a thinner fluid that flows more easily. Factors influencing viscosity include temperature, molecular size, and intermolecular forces.

Intermolecular Forces

Intermolecular forces are the attractive forces between molecules that influence physical properties such as boiling point, melting point, and viscosity. These forces include hydrogen bonding, dipole-dipole interactions, and London dispersion forces. Substances with stronger intermolecular forces typically exhibit higher viscosity due to the increased energy required to overcome these attractions during flow.

Hydroxyl Group

The hydroxyl group (-OH) is a functional group found in alcohols, such as 1-hexanol. This group is capable of forming hydrogen bonds, which significantly increases the viscosity of the substance compared to hydrocarbons like hexane that lack such polar functional groups. The presence of the hydroxyl group enhances intermolecular interactions, leading to a thicker, more viscous liquid.