Compounds with nearly identical molar masses often have very...

Name: Problem 49, Chapter 15: CHEMISTRY: The Molecular Nature of Matter and Change
Uploaded: 2020-07-08T20:06:53-08:00
Duration: 1 min 25 s
Channel: Dalton Hilovsky
Description: Compounds with nearly identical molar masses often have very different physical properties. Choose the compound with the higher value for each of the following properties, and explain your choice. (a) Solubility in water: chloroethane or methylethylamine (b) Melting point: diethyl ether or 1 -butanol (c) Boiling point: trimethylamine or propylamine

Compounds with nearly identical molar masses often have very different physical properties. Choose the compound with the higher value for each of the following properties, and explain your choice. (a) Solubility in water: chloroethane or methylethylamine (b) Melting point: diethyl ether or 1 -butanol (c) Boiling point: trimethylamine or propylamine

Compounds with nearly identical molar masses often have very different physical properties. Choose the compound with the higher value for each of the following properties, and explain your choice.
(a) Solubility in water: chloroethane or methylethylamine
(b) Melting point: diethyl ether or 1 -butanol
(c) Boiling point: trimethylamine or propylamine

Key Concepts

Structure-Property Relationships

Structure-property relationships refer to the understanding that small differences in molecular structure, such as the presence or absence of certain functional groups or changes in molecular geometry, can lead to significant variations in physical properties. This concept underpins the evaluation of substances with similar molar masses but differing physical behavior based on their intermolecular interactions.

London Dispersion Forces

London dispersion forces are the weakest intermolecular forces but are present in all molecules, especially in nonpolar compounds. Their strength increases with the number of electrons and the size of the molecule, influencing properties such as boiling and melting points, particularly when other stronger intermolecular forces are absent.

Intermolecular Forces

Intermolecular forces are the forces of attraction or repulsion between molecules that determine many physical properties such as boiling points, melting points, and solubility. These forces include hydrogen bonding, dipole-dipole interactions, and London dispersion forces, and a molecule’s ability to engage in these interactions depends on its functional groups and molecular structure.

Hydrogen Bonding

Hydrogen bonding is a particularly strong type of dipole-dipole interaction that occurs when hydrogen is bonded to highly electronegative atoms like nitrogen, oxygen, or fluorine. Molecules capable of hydrogen bonding tend to exhibit higher boiling and melting points and enhanced solubility in polar solvents like water compared to molecules that cannot form such bonds.

Dipole-Dipole Interactions

Dipole-dipole interactions occur between molecules that possess a permanent dipole moment, leading to attractive forces between the positive end of one molecule and the negative end of another. Although these interactions are generally weaker than hydrogen bonds, they still significantly affect physical properties by increasing boiling and melting points.

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