Comparing Boiling Pts of Bromine & Iodine Monochloride - Intermolecular Forces

In summary, there is a difference in the boiling points of bromine (Br2) and iodine monochloride (ICl) due to their respective polarities. While both substances have the same number of electrons and thus the same strength of London dispersion forces, iodine monochloride has a stronger dipole-dipole force due to the difference in electronegativities between its atoms. This results in a higher boiling point for ICl compared to Br2.
  • #1
mujahid613
1
0
I have been trying to get my head around this question, but do not understand it.

Consider the two isoelectronic substances, bromine (Br2) and Iodine monochloride (ICl). Based upon your knowledge of intermolecular forces, explain the difference in their boilings pts. (Bromine: 59 degrees C; iodine monochloride: 97 degrees C)

Well, I know that both bromine and iodine monochloride have 70 electrons per molecule, therefore, the strength of the London dispersion forces between the molecules of each should be the same. Now, what I'm not sure of is how to assess their polarities.

VSPER Theory doesn't really help me out because they are both of the same shape, so one would assume that they would both be either polar or non-polar.

However, if I assess their respective electronegativities...

BR-BR (must be the same; therefore has to be non-polar?)
I-CL (is different; therefore polar?)

Therefore, ICL should have stronger dipole-diple-force, and a higher boiling point.

Are these conclusions justified?

Thanks for your prompt response.
 
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  • #2
Looks good to me! You may want to wait for a more qualified person to confirm, but that's probably how I would've gone about doing it.
 
  • #3
Yeah, I think that's a good assessment. Although the london dispersion interactions relate to the polarity of the molecule, in that you'll need to consider the individual atoms and their quantum numbers. The farther away an electron is from the nucleus, the effective nuclear charge is relatively less, the electron is not being held as strongly. The orbit is farther away from the nucleus (quantum number) and there's relatively more electron shielding.
 

1. What are the intermolecular forces present in bromine and iodine monochloride?

The intermolecular forces present in bromine and iodine monochloride are London dispersion forces, dipole-dipole interactions, and induced dipole-induced dipole interactions.

2. Which intermolecular force is the strongest between bromine and iodine monochloride?

The strength of intermolecular forces depends on factors such as molecular size and polarity. In general, London dispersion forces are the weakest, while dipole-dipole interactions and induced dipole-induced dipole interactions are stronger. It is difficult to determine which specific force is strongest between bromine and iodine monochloride without further information about the molecules' properties.

3. How do the intermolecular forces affect the boiling points of bromine and iodine monochloride?

The strength of intermolecular forces directly affects the boiling point of a substance. Stronger forces require more energy to break, resulting in a higher boiling point. Therefore, the presence of stronger intermolecular forces in bromine and iodine monochloride contributes to their relatively high boiling points compared to other molecules of similar size.

4. Why does bromine have a higher boiling point than iodine monochloride?

The difference in boiling points between bromine and iodine monochloride can be attributed to the differences in their molecular size and polarity. Bromine is larger than iodine monochloride, and it also has more electrons, resulting in stronger London dispersion forces. Additionally, bromine is a nonpolar molecule, while iodine monochloride has a dipole moment, leading to stronger dipole-dipole interactions in bromine.

5. How can the boiling points of bromine and iodine monochloride be compared experimentally?

The boiling points of substances can be compared experimentally using a variety of methods, such as a boiling point apparatus or a distillation setup. These methods involve heating the substances and observing the temperature at which they change from a liquid to a gas. The substance with the higher boiling point will require more energy to reach this phase change, and therefore, will have a higher boiling point. Comparing the boiling points of bromine and iodine monochloride in this way would show that bromine has a higher boiling point due to its stronger intermolecular forces.

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