11.1 Intermolecular Forces

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@paymunpezeshkpour2375 5 жыл бұрын

Hi, I just had a question regarding the "H2S, H2Se and H2Te" example! You mention that He2Te is the one with the highest boiling point because its relative size and thus london dispersion forces are greatest among the listed examples and in this case london forces trumps the Dipole-Diople forces. I was wondering how are we to determine the point where london dispersion forces out weigh the dipole diople forces? (ie given a list of a non H-bonding polar molecules when can we say that the london forces play a larger role in the intermolecular forces when compared to the dipole-dipole forces?) Thank you in advance!!

@ChadsPrep 5 жыл бұрын

It's difficult to draw a hard line for comparison, but we typically tell students that if two compounds are very close in size then the more polar one will have greater intermolecular forces. So then we have to define "very close in size." Unfortunately we usually don't but instead only give students comparisons involving compounds of nearly identical molecular weights or fairly different molecular weights. A good rule of thumb I've found is if a molecule is more than 20% larger than it will have greater intermolecular forces than a more polar, but lighter molecule (assuming no hydrogen bonding is involved). It's really more complicated than this as we have to take into account surface area and polarizability of larger atoms, but we don't typically try to give students such complicated examples. Hope this helps!

@deborahaigbedion6323 2 жыл бұрын

can you please describe the difference between vapor pressure and heat of vaporization? Because stronger intermolecular forces lead to a higher boiling point, higher heat of vaporization, higher viscosity, higher surface tension, and lower vapor pressure

@ChadsPrep 2 жыл бұрын

Vapor pressure is a measure of the quantity of particles that are in the gas phase above a liquid or solid at a given temperature. Vapor pressure rises with temperature, and the key here is that this does not need to refer to the boiling temperature (and typically doesn't ). But the heat of vaporization is the amount of heat required to boil a liquid when at its boiling temperature. Hope this helps!

@deborahaigbedion6323 2 жыл бұрын

@@ChadsPrep Thank you

@ChadsPrep 2 жыл бұрын

@@deborahaigbedion6323 You're welcome.

@andrewchristie2997 4 жыл бұрын

Chad, in Chap 11 in most books there is alot of complex info on Solids, Lattice Structures and Closest packing. Any chance on a video covering these topics?

@ChadsPrep 4 жыл бұрын

Sorry Andrew, the only place I have those videos available is in my premium course on chadsprep.com. I just made them part of the Free Preview so that you could access them for free. Use the following link: courses.chadsprep.com/enroll/18908?et=free_trial

@devikanair44 4 жыл бұрын

@@ChadsPrep I just signed up I'm super stoked! you're an excellent teacher and I've learned so much. I'm hopeful to be more comfortable with these topics!