Boiling point question.?

Question

How do you find the boiling point. I read up on Wikipedia and my chem book and I can't find out how to do it. Thanks very much...chem homework is really driving me crazy today.

I have the following problem:

Which substance will have the highest boiling point?

a. They will all have similar boiling points because they have similar molar masses.
b. CH3CH2CH3
c. CH3Cl
d. CH3CH2OH

Answer 1

d) due to Hydrogen bonding

Answer 2

Water has a higher freezing point and a melting point because of the very strong attraction between water molecules, giving rise to the formation of hydrogen bonds. But it's surprising to find that RMM (relative molecular mass) of similar other compounds like water, which has H2O=18 compared with Methane (RMM=16), Ammonia (RMM=17) are ALL gases at zero degrees except water, which is at it's solid state. The reason is as above, in addition, it has a high latent heat of vaporization, requiring a GREAT deal of energy to over some the forces of attraction between the molecules, allowing them to change from solid to liquid, and liquid to gas. Hope this helps!

Answer 3

Well, you could look up each substance's b.p., but I don't really think that's the point of the question.

The boiling point of a substance is determined not only by its molecular weight, but also by the strength of the interactions between molecules in the liquid phase. The stronger these interactions are, the highest its boiling point is. That's why polar compunds show very high boiuling points in comparison with non-polar ones.

Therefore, without knowing the exact value of the coumpunds' b.p.s, one could easily predict that they will be, from lowest to highest:

1. propane
2. chloromethane
3. ethanol

Answer 4

Well, let's see:

Compound b is propane: MW = 44.10 g/mol; BP = -42.1°C
Compound c is chloromethane: MW = 50.49 g/mol; BP = -24.0°C
Compound d is ethanol: MW = 46.07 g/mol; BP = 78.2°C

So, what's the answer? D!

Ethanol has the highest boiling point because of the hydroxyl group (which is what makes it an alcohol). This group can undergo some weak hydrogen bonding, which means it resists separation better, so it will boil at a higher temperature.

Hope that helps.

Answer 5

The greater the forces of attraction the higher the boiling point or the greater the polarity the higher the boiling point.

Answer 6

CH3CH2OH will have the highest boiling point. Then CH3Cl. Then finally CH3CH2CH3.

Here's the actual numbers:
CH3Cl = −24.22 °C
CH3CH2CH3= −42.09 °C
CH2CH2OH = 78.4 °C

Answer 7

i belive that the more branched a molecule is the higher its boiling point is....ie the more bonds there are that have to be broken. i'm not 100% on that. so i would say that B) would have the higher boiling point.