Question

1. Identify the types of intermolecular forces present in the following molecules

Diethyl ether: CH3CH2-O-CH2CH3 Butanol: CH3CH2CH2CH2OH Butane: CH3CH2CH2CH3

2. Rank the compounds in terms of their relative strength of intermolecular interaction

3. Indicate how the boiling point changes as the strength of intermolecular forces increases

4. Compare the boiling points of methanol, ethanol, and propanol. In terms of intermolecular forces why does the boiling point increase as the molecular weight increases

Methanol: CH3OH Ethanol: CH3CH2OH Propanol: CH3CH2CH2OH

Answer 1

1. Identify the types of intermolecular forces present in the following molecules

Diethyl ether: CH3CH2-O-CH2CH3 --> this is nonpolar, thereofre only london dispersion forces are present.

London dispersion forces are present in all mass due to the presence of electrons and protons interacting between each other

Butanol: CH3CH2CH2CH2OH --> Hydrogen bonding between H and OH groups; this must be polar, since it has a OH group which is negatively charged and the chain of carbons, positively charged, and as well as london dispersion forces

Butane: CH3CH2CH2CH3

this is nonpolar, thereofre only london dispersion forces are present.

London dispersion forces are present in all mass due to the presence of electrons and protons interacting between each other

2. Rank the compounds in terms of their relative strength of intermolecular interaction

CH3CH2CH2CH2OH >> CH3CH2-O-CH2CH3 > CH3CH2CH2CH3

Hbonding + Dipoles are much stronger than dispersion forces

Now, between the ether vs. alkane, the ether has a higher mass, thereofre, higher interactions between the species, so higher BP

3. Indicate how the boiling point changes as the strength of intermolecular forces increases

CH3CH2CH2CH2OH >> CH3CH2-O-CH2CH3 > CH3CH2CH2CH3

H-bonding + Dipoles require plenty of energy to be broken, therefore the BP is high, and it takes much more energy to break the interactions....

Dispersion forces are weak, so they are easily broken...

4. Compare the boiling points of methanol, ethanol, and propanol. In terms of intermolecular forces why does the boiling point increase as the molecular weight increases

Methanol: CH3OH --> lower, since it has a lower mass; plenty of dipole interaciton

Ethanol: CH3CH2OH   --> middle , since it has a middle in mass; some of dipole interaciton

Propanol: CH3CH2CH2OH  --> higher , since it has a higher mass; some of dipole interaciton