Podcast
Questions and Answers
The attractive force called the London dispersion force is one of the three types of ______ forces.
The attractive force called the London dispersion force is one of the three types of ______ forces.
van der Waals
The dispersion force is named in honor of physicist Fritz ______.
The dispersion force is named in honor of physicist Fritz ______.
London
Dispersion forces become significant only when molecules are very ______.
Dispersion forces become significant only when molecules are very ______.
close
Larger and heavier atoms exhibit stronger dispersion forces than ______ atoms.
Larger and heavier atoms exhibit stronger dispersion forces than ______ atoms.
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In a polar molecule like hydrogen chloride, the Cl atom bears a partial ______ charge.
In a polar molecule like hydrogen chloride, the Cl atom bears a partial ______ charge.
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Dipole-dipole attractions occur due to the attraction between the positive end of one molecule and the negative end of another, such as in ______.
Dipole-dipole attractions occur due to the attraction between the positive end of one molecule and the negative end of another, such as in ______.
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Nonpolar molecules such as F2 do not have a permanent ______ charge separation.
Nonpolar molecules such as F2 do not have a permanent ______ charge separation.
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When comparing HCl to nonpolar molecules, both substances have approximately the same molecular ______.
When comparing HCl to nonpolar molecules, both substances have approximately the same molecular ______.
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HCl has a higher normal boiling point of ______ K compared to F2 which is ______ K.
HCl has a higher normal boiling point of ______ K compared to F2 which is ______ K.
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The attractions between HCl molecules are known as - attractions.
The attractions between HCl molecules are known as - attractions.
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Water (H2O) has a lower molecular mass of ______ amu than nitrosyl fluoride (ONF), which has a mass of ______ amu.
Water (H2O) has a lower molecular mass of ______ amu than nitrosyl fluoride (ONF), which has a mass of ______ amu.
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Hydrogen bonding is a particularly strong type of - attraction.
Hydrogen bonding is a particularly strong type of - attraction.
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Molecules with ______-H, O-H, or N-H moieties experience strong hydrogen bonding.
Molecules with ______-H, O-H, or N-H moieties experience strong hydrogen bonding.
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Hydrogen bonds are about ______ to ______% as strong as covalent bonds.
Hydrogen bonds are about ______ to ______% as strong as covalent bonds.
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The weaker dispersion forces between nonpolar F2 molecules are insufficient to keep them in a ______ state.
The weaker dispersion forces between nonpolar F2 molecules are insufficient to keep them in a ______ state.
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The large difference in boiling points between H2O and ONF cannot solely be attributed to ______ forces.
The large difference in boiling points between H2O and ONF cannot solely be attributed to ______ forces.
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Study Notes
Dispersion Forces
- One of the three types of van der Waals forces, present in all condensed phases.
- Named after physicist Fritz London, who explained the forces in 1928.
- Also known as London dispersion forces or simply dispersion forces.
- Atoms and molecules can develop temporary dipoles due to the constant motion of electrons.
- Temporary dipoles can induce dipoles in neighboring atoms or molecules, leading to attractive forces.
- These forces are relatively weak and significant only at close distances.
- Larger, heavier atoms and molecules exhibit stronger dispersion forces.
- Example: F2 and Cl2 are gases at room temperature; Br2 is a liquid; I2 is a solid, reflecting varying strengths of dispersion forces.
Dipole-Dipole Attractions
- Occur between polar molecules, which have distinct partial positive and negative charges.
- Example: In hydrogen chloride (HCl), Cl has a partial negative charge, while H has a partial positive charge.
- The attraction between the positive end of one HCl molecule and the negative end of another leads to dipole-dipole attraction.
- Comparison of HCl and nonpolar F2 demonstrates that dipole-dipole attractions create stronger intermolecular forces than dispersion forces.
- Both HCl and F2 can have similar properties (number of atoms and molecular mass), but boiling points differ significantly: HCl has a boiling point of 188 K, and F2 is 85 K.
- The strength of dipole-dipole attractions correlates with boiling points, freezing points, and enthalpies of vaporization or fusion.
Hydrogen Bonding
- Occurs in polar molecules with hydrogen atoms bonded to highly electronegative elements (F, O, N).
- Example: Nitrosyl fluoride (ONF) is a gas at room temperature, while water (H2O) is a liquid despite having a lower molecular mass.
- The disparity in boiling points between ONF and H2O is not due to dispersion forces or dipole moments but rather to hydrogen bonding.
- Hydrogen bonds arise from the significant electronegativity difference between hydrogen and the bonding electronegative atom (F, O, or N).
- Characterized by highly concentrated partial charges and strong intermolecular attractions.
- Hydrogen bonds, despite being termed "bonds," are intermolecular forces, significantly weaker than covalent bonds (5-10% as strong) but stronger than typical dipole-dipole attractions and dispersion forces.
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Description
Explore the concept of dispersion forces, one of the three van der Waals forces present in all condensed phases. This quiz delves into the London dispersion force, its significance, and the motion of electrons that contribute to this attractive force. Test your understanding of this fundamental chemical phenomenon.
