Evaporation and intermolecular

2013-10-20 5:04 pm

Evaporation and intermolecular attractions problems

1. What are some structural features of a substance that might influence
its ability to evaporate? For instance, compare the two substances
below and list at least three different structural features that might
lead to differences in their properties:

Compound Formula

octane C8H14

2-butanol C4H10O

2. A substance evaporates from the surface of a temperature probe. What
do you think happens to the temperature of the probe—does it increase
or decrease? Explain.

3. What does the term “volatility” mean? What does it mean for Substance
A to be more volatile than Substance B?

4. The temperature of the probe changes as the substance evaporates. The
more evaporation there is, the greater the change in temperature.
Which will produce a larger change in temperature (ΔT): a more volatile
substance or a less volatile substance? Explain.

5. Based on #4 above, true or false: A large change in temperature (ΔT)
indicates that strong attractions are present in the evaporating
substance. Explain.

回答 (1)

用戶4366

2013-10-21 5:58 am

✔ 最佳答案

1. I can only list 2 factors. sorry !

1. Intermolecular force.
2-butanol C₄H₁₀O is held by hydrogen bonding while octane is held by Van Der Waak's force. B.P. of 2-butanol > octane. Actually, this is the predominent factor for this comparision.
Molecular mass of 2-butanol = 74 and octane = 86
The larger molecular mass of octane predicts octane to has a higher B.P. But actually 2-butanol has higher B.P. ==> this is a minor factor in this comparision.

The symmetry of molecule would has influence to M.P. but not B.P. So, I can list only 2 factors.

2. It decrease the temperature of the probe, it cools down the probe. As the substance evaporates, it absorbs heat from the probe as the latent heat for the evaporation.

3. It means substance A evaporate more easily than B OR A has a lower B.P. than B.

4. The more volatile one.

5. False, it indicates a weaker intermolecular force.

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