Rank the following atoms or molecules in order of increasing strength of intermolecular forces in the pure substance. which exists as a gas at 25 degrees Celisus and 1 atm?
a. Ne
b. CH4
c. CO
d. CCl4
Please help me and show how you got it so i can understand this, thanks so much in advance!
a. Ne
b. CH4
c. CO
d. CCl4
Please help me and show how you got it so i can understand this, thanks so much in advance!
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Well, we should review the three types of IMFs. The weakest IMF is London forces a.k.a dispersion forces. Everything has London forces. The strength of London forces increases as the number of electrons increases. The next strongest IMF is dipole-dipole attractions. These occur between polar molecules. As the polarity of a molecule increases, the strength of dipole-dipole attractions increases. The strongest IMF is hydrogen bonding. Hydrogen bonding occurs between molecules that have H bonded to N, O or F. Hydrogen bonding is actually a subset of dipole-dipole attractions, i.e. Hydrogen bonding is a very strong type of dipole-dipole attractions.
a. Ne
The attractions between Ne atoms only involves London forces.
b. CH4
There are London forces. Methane is not polar because the electronegativities of C and H are almost the same and the molecular geometry is symmetrical.
d. CCl4
There are London forces only. Even though the bond between the C atom and a Cl atom is polar, the molecule is not polar. This is because the molecule is symmetrical.
When we look at Ne, CH4 and CCl4, they all have London forces only. So, you have to compare the number of TOTAL electrons of each substance. Ne has 10 e-. CH4 has a total of 10 e-. CCl4 has a total of 74 e-. How do we tell between Ne and CH4 which has the stronger London forces if they have the same number of e-? We look at the electronegativities. Two Ne atoms will have the same ENs. A C atom and an H atom, however, have different ENs. Since there is a greater difference in ENs between C and H, CH4 has stronger London forces than Ne.
c. CO
There are London forces and dipole-dipole attractions. CO is a polar molecule. Unlike the other atoms/molecules, which only had London forces, CO additionally has dipole-dipole attractions which are stronger than London forces.
a. Ne
The attractions between Ne atoms only involves London forces.
b. CH4
There are London forces. Methane is not polar because the electronegativities of C and H are almost the same and the molecular geometry is symmetrical.
d. CCl4
There are London forces only. Even though the bond between the C atom and a Cl atom is polar, the molecule is not polar. This is because the molecule is symmetrical.
When we look at Ne, CH4 and CCl4, they all have London forces only. So, you have to compare the number of TOTAL electrons of each substance. Ne has 10 e-. CH4 has a total of 10 e-. CCl4 has a total of 74 e-. How do we tell between Ne and CH4 which has the stronger London forces if they have the same number of e-? We look at the electronegativities. Two Ne atoms will have the same ENs. A C atom and an H atom, however, have different ENs. Since there is a greater difference in ENs between C and H, CH4 has stronger London forces than Ne.
c. CO
There are London forces and dipole-dipole attractions. CO is a polar molecule. Unlike the other atoms/molecules, which only had London forces, CO additionally has dipole-dipole attractions which are stronger than London forces.
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a,b,d,c
First start with the non-polar molecules. Of these the ones with the least number of electrons would have the less momentary dipoles.
The polar molecule would have the greatest attractions.
First start with the non-polar molecules. Of these the ones with the least number of electrons would have the less momentary dipoles.
The polar molecule would have the greatest attractions.