Chemistry Problem Dealing With Miscible Substances

Chemistry Question of Miscible?

Methanol is not miscible with hexane. I've actually seen it form two layers of liquid in the lab. I don't have direct experience with 1-pentanol + hexane, but theoretically it would be miscible. That being said, here is the explanation.

It has to do with hydrogen bonding, and the principle of "like dissolves like". Both methanol and 1-pentanol are capable of forming hydrogen bonds. But methanol has only one carbon per OH grroup, and the percentage of its surface that is capable of participating in hydrogen bonding is high, about 50%. This is why it mixes with water, and why it doesn't mix with alkanes such as hexane. 1-pentanol also has an OH group, but the rest of the molecule is hydrocarbon-like and so 1-pentanol will mix with hydrocarbons and only partially mixes with water. An alcohol with even more carbons, like 1-octanol, will be immiscible with water.

What are some examples of miscible substances? And how can you determine what is miscible and what is not?

The formula itself may not tell you, but drawing its Lewis structure definitely will. The rule "like dissolves like" is key here; it means that polar molecules will be miscible in polar molecules, and nonpolar will be miscible with other nonpolar molecules. Sometimes structures that appear polar and nonpolar can be miscible, but without limit, polar+polar and nonpolar+nonpolar.

Examples:
Polar+polar: H2O and acetone. They both have big dipole moments, which tips you off.
H2O and alcohols like CH3OH and CH3CH2OH: again, both have dipole moments and are very polar.

However, H2O and CH3CH2OCH2CH3 (diethyl ether) are NOT miscible, because H2O has a dipole moment and diethyl ether does not (the oxygen is right in the middle so the dipoles cancel).

Nonpolar+nonpolar: hexane (CH3CH2CH2CH2CH2CH3, or C6H14) and diethyl ether are miscible.

Questions about miscibility (chemistry)?

miscibility is solubility. basically, will one substance dissolve in the other.

a) alcohol and water. miscible, because they are both polar with hydrogen bonds.
b) yes because they are both hydrophobic (not polar)
c) no because one is polar (hydrophilic) and one is not (hydrophobic)
d) One's ionic, one's polar. Think about it.

Miscible substances cannot dissolve in one another.?

True.
Petrol , diesel are miscible
water , alcohol, acetone are miscible.
But water , petrol, diesel are not miscible.