How to determine which of the compounds will have the lowest boiling point vs the highest boiling point?
another question:
Which of the following solutions will have the largest temperature range for the liquid state?
1) 1M C3H8? (ethanol)
2)1M CH3COOH (acetic acid)
3) 1M KBr(Potassium Bromide)
4) 1M MgBr2 (Magnesium Bromide)
I answered b, since it was the largest molecule, thought. How do i approach this question.
BY the way I have a chem final tomorrow, so i might be asking questions throughout the day.
#2 question is one on the colligative properties of liquid; i.e., remember
delta Tf = i*Kf*molality
delta Tb = i*Kb*molality
So the one with the largest range will be the one that i*K*m is the highest.
Since K is constant for each salt and m is constant fo reach salt, the only difference is i.
Which has the largest i value. (By the way, C3H8 is NOT ethanol. C3H8 is propane; C2H5OH is ethanol).
the largest I value would be MgBr2 because it has 3 ions, KBr has 2, and the other 2 are - to 1 because they do not split, correct?
What about my first question? About determining BP highest or lowest. Does the same principle apply?
You are correct that MgBr2 will have the highest range because i=3.
For #1, the same approach applies.
The largest boiling point will be the one with the highest i.
The lowest boiling point depends upon if C3H8 actually is C2H5OH or not. If so, it's a toss up between 1 and 2. Both ethanol and CH3COOH have i = 1 (theoretical) but we know CH3COOH ionizes about 1% or so and that would make me pick ethanol (which has no ionization) over CH3COOH (which has a little). In terms of i, i = 1 for ethanol but perhaps 1.1 for CH3COOH.
ok thank you. It is ethanol, not propane o that would make sense.
To determine which compound will have the lowest or highest boiling point, we need to consider several factors:
1. Intermolecular forces: Boiling points primarily depend on the strength of intermolecular forces between molecules. The three main types of intermolecular forces are van der Waals forces, dipole-dipole interactions, and hydrogen bonding. In general, stronger intermolecular forces result in higher boiling points.
2. Molecular weight: Larger molecules tend to have higher boiling points due to increased surface area and more extensive intermolecular interactions.
3. Molecular polarity: Polar molecules have stronger intermolecular forces due to the attraction between their positive and negative regions. As a result, polar molecules generally have higher boiling points compared to nonpolar molecules of similar size.
4. Hydrogen bonding: Hydrogen bonding is a strong intermolecular force that occurs when a hydrogen atom is bonded to a highly electronegative atom (such as oxygen, nitrogen, or fluorine). Compounds that can form hydrogen bonds tend to have higher boiling points.
5. Branching and symmetry: Branched molecules generally have lower boiling points compared to straight-chain isomers because the branching disrupts intermolecular interactions. Similarly, molecules with more symmetry tend to have lower boiling points.
Considering these factors, you can compare the compounds and determine which one is likely to have the lowest or highest boiling point. However, it's important to note that these rules provide a general guideline and there can be exceptions. To get an accurate determination, it is often necessary to consult experimental data or use computational methods to calculate boiling points.