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The correct answer is B. Can anyone explain why? Thanks!
EK 30 Min CHEM 1 lecture
- Thread starter joe_1395
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London dispersion forces are just very weak dipole forces between induced dipoles. Some molecules have permanent dipoles, like water. These dipoles always exist and so the molecules will orient themselves accordingly. Other molecules don't have dipoles. Thus, they really don't attract or repel each other. However, if you put two of them close enough together, their electron clouds will reorient themselves such that energy is minimized, i.e. a dipole will be induced. Because you have to induce these dipoles (these molecules, when left alone, don't really want to form dipoles), London dispersion forces are weaker than permanent dipole-dipole interactions.
C is incorrect because dispersion forces always exist. D is incorrect because dipole-dipole interactions occur in covalent compounds as well, such as H2O or any asymmetric molecule with atoms with significantly different electronegativities bonded together. A is incorrect because dipoles aren't really static point charges.
C is incorrect because dispersion forces always exist. D is incorrect because dipole-dipole interactions occur in covalent compounds as well, such as H2O or any asymmetric molecule with atoms with significantly different electronegativities bonded together. A is incorrect because dipoles aren't really static point charges.
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Why is it only dispersion forces are permanent?
Because while not everything has a permanent dipole, you can always induce a dipole in something by moving something else near it. "Permanent" is also not a good word to use to describe dispersion forces. They are precisely impermanent, or temporary.
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Sorry, by permeant I guess I mean always possible or always present in some way. For example, every solution will have London forces present, but they may be insignificant compared to other forces present. That close?
Yes, dispersion forces will always be present so they by themselves usually don't explain any unusual phenomena. They explain, for example, why lipids cling together in the biological membranes. But they don't explain why water boils at a high temperature compared to light hydrocarbons. Water has dispersion forces too, but it's the H-bonding that makes it different.