In each pair, choose the compound you would expect to have the highest boiling/melting point.
(c)

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Step 1: Understand the factors that influence boiling and melting points. These include intermolecular forces (such as hydrogen bonding, dipole-dipole interactions, and London dispersion forces), molecular weight, and molecular symmetry.

Step 2: Analyze the compounds in the pair provided. Compare their molecular structures to determine the types and strengths of intermolecular forces present in each compound.

Step 3: Consider hydrogen bonding. If one compound has functional groups capable of hydrogen bonding (e.g., -OH, -NH2), it will likely have a higher boiling/melting point due to stronger intermolecular forces.

Step 4: Evaluate molecular weight. Larger molecules generally have higher boiling/melting points because they exhibit stronger London dispersion forces.

Step 5: Assess molecular symmetry. Symmetrical molecules tend to pack more efficiently in a solid state, leading to higher melting points, while asymmetry can affect boiling points due to differences in intermolecular interactions.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Intermolecular Forces

Intermolecular forces are the attractive forces between molecules that influence physical properties like boiling and melting points. The main types include hydrogen bonding, dipole-dipole interactions, and London dispersion forces. Compounds with stronger intermolecular forces generally exhibit higher boiling and melting points due to the increased energy required to overcome these attractions.

Molecular Weight

Molecular weight refers to the mass of a molecule, which can affect its boiling and melting points. Generally, larger molecules with greater molecular weights have higher boiling and melting points because they have more electrons, leading to stronger London dispersion forces. However, this trend can be influenced by the presence of functional groups and molecular structure.

Functional Groups

Functional groups are specific groups of atoms within molecules that determine the chemical properties and reactivity of those molecules. Different functional groups can significantly affect boiling and melting points due to their ability to engage in hydrogen bonding or other interactions. For example, alcohols typically have higher boiling points than hydrocarbons of similar molecular weight due to the presence of hydroxyl (-OH) groups that can form hydrogen bonds.

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