Domanda del libro di testo
(b) What is the relationship between viscosity and temperature?
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Ch.11 - Liquids and Intermolecular Forces
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232
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TOC.tableOfContents
- Ch.1 - Introduction: Matter, Energy, and Measurement177
- Ch.2 - Atoms, Molecules, and Ions231
- Ch.3 - Chemical Reactions and Reaction Stoichiometry216
- Ch.4 - Reactions in Aqueous Solution189
- Ch.5 - Thermochemistry175
- Ch.6 - Electronic Structure of Atoms168
- Ch.7 - Periodic Properties of the Elements150
- Ch.8 - Basic Concepts of Chemical Bonding177
- Ch.9 - Molecular Geometry and Bonding Theories200
- Ch.10 - Gases179
- Ch.11 - Liquids and Intermolecular Forces113
- Ch.12 - Solids and Modern Materials154
- Ch.13 - Properties of Solutions157
- Ch.14 - Chemical Kinetics199
- Ch.15 - Chemical Equilibrium128
- Ch.16 - Acid-Base Equilibria164
- Ch.17 - Additional Aspects of Aqueous Equilibria163
- Ch.18 - Chemistry of the Environment105
- Ch.19 - Chemical Thermodynamics164
- Ch.20 - Electrochemistry171
- Ch.21 - Nuclear Chemistry122
- Ch.22 - Chemistry of the Nonmetals82
- Ch.23 - Transition Metals and Coordination Chemistry79
- Ch.24 - The Chemistry of Life: Organic and Biological Chemistry16
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Non è quello che usi tu?Cambia libro di testo
Capitolo 11, Problema 32
The generic structural formula for a 1-alkyl-3-methylimid- azolium cation is where R is a -CH2(CH2)nCH3 alkyl group. The melting points of the salts that form between 1-alkyl-3-methylimidazolium cation and the PF6- anion are as follows: R = CH2CH3 (m.p. = 60 °C), R = CH2CH2CH3 (m.p. = 40 °C), r = CH2CH2CH2CH3 (m.p. = 10 °C), and R = CH2CH2CH2CH2CH2CH3 (m.p. = -61 °C). Why does the melting point decrease as the length of alkyl group increases?
Guida verificata passo dopo passo1
Identify the trend in melting points as the alkyl chain length increases: the melting point decreases.
Understand that the melting point is influenced by the strength of intermolecular forces in the solid state.
Recognize that longer alkyl chains increase the hydrophobic character and disrupt the packing efficiency of the ions in the solid state.
Explain that as the alkyl chain length increases, the van der Waals forces become more significant, but the overall packing becomes less efficient, leading to a decrease in melting point.
Conclude that the decrease in melting point with increasing alkyl chain length is due to the reduced packing efficiency and increased disorder in the solid state.
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Intermolecular Forces
Intermolecular forces are the attractive forces between molecules that influence physical properties such as melting and boiling points. In ionic compounds, like the salts formed from 1-alkyl-3-methylimidazolium cations and PF6- anions, the strength of these forces is crucial. As the alkyl chain length increases, the overall molecular size increases, which can lead to weaker interactions due to increased distance between charged regions.
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Percorso guidato
01:59
Intermolecular vs Intramolecular Forces
Hydrophobic Effect
The hydrophobic effect refers to the tendency of nonpolar substances to aggregate in aqueous solutions to minimize their exposure to water. In the context of ionic liquids, longer alkyl chains are more hydrophobic, which can disrupt the packing of ions in the solid state. This disruption can lead to a decrease in the melting point as the solid structure becomes less stable with longer, bulkier alkyl groups.
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02:31Photoelectric Effect
Crystal Lattice Energy
Crystal lattice energy is the energy released when ions in the gas phase come together to form a solid ionic compound. It is a measure of the stability of the ionic lattice. As the alkyl chain length increases, the lattice energy may decrease due to the larger size and lower charge density of the cation, resulting in weaker ionic interactions and a lower melting point for the resulting salts.
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00:53Lattice Energy
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