Question

Water interacts with polar substances like –OH groups but not with non-polar substances like methyl (-CH3) or ethyl groups (-CH2). Using this information, select the molecules that will easily dissolve in water based on polarity not on size. Check all that apply.

A.) CH4
B.) CH3OH
C.) CH3 CH3
D.) CH3 CH2 CH2 OH
E.) CH3 CH2 CH2 CH2 CH2 CH3

Answer 1

Molecules that contain polar functional groups like -OH will dissolve in water; hence, CH3OH and CH3CH2CH2OH will be soluble. Non-polar molecules without such groups, like CH4, CH3CH3, and CH3CH2CH2CH2CH2CH3, will not dissolve in water.

Step-by-step explanation:

When selecting molecules that will easily dissolve in water based on polarity and not size, we should look for molecules with polar functional groups such as the -OH (hydroxyl) group, which is hydrophilic because it can form hydrogen bonds with water. From the given options:

• B.) CH3OH (Methanol) has an -OH group that is polar and can interact with water, making it soluble or miscible in water.
• D.) CH3 CH2 CH2 OH (Propanol) has a longer hydrocarbon chain than methanol, but it still contains an -OH group that is polar and can form hydrogen bonds with water, thus it will also dissolve in water, although its solubility will be less than that of methanol.

On the contrary, A.) CH4 (Methane), C.) CH3 CH3 (Ethane), and E.) CH3 CH2 CH2 CH2 CH2 CH3 (Hexane) are non-polar molecules because they lack polar functional groups and instead have alkyl groups like methyl (-CH3) or ethyl (-CH2), which are hydrophobic. Thus, these substances will not dissolve easily in water.

Answer 2

The compounds CH4, CH3 CH3 and CH3CH2CH2CH2CH2CH3, do not have -OH groups linked to C atoms, so they are not polar, and based of the criterium given they will not interact well with water, meaning they will not easily dissolve in water. On the other hand, CH3OH and CH3CH2CH2OH meet the criterium of polarity (they contain the group -OH) so these two substances (alcohols) will easily dissolve in water. So you have to check the options B. and D.