Question

Assertion (a): Dimethyl ether is less volatile than ethyl alcohol.

Reason (r): Dimethyl ether has greater vapor pressure than ethyl alcohol.

a) Both (a) and (r) are true, and (r) is the correct explanation of (a).

b) Both (a) and (r) are true, but (r) is not the correct explanation of (a).

c) (a) is true, but (r) is false.

d) (a) is false, but (r) is true.

Answer 1

Dimethyl ether is more volatile than ethyl alcohol because it lacks hydrogen bonding, leading to weaker intermolecular forces and a higher vapor pressure.

Step-by-step explanation:

The assertion that dimethyl ether is less volatile than ethyl alcohol is false; therefore, the correct answer is (a) is false, but (r) is true. Dimethyl ether (CH3OCH3) and ethyl alcohol (C2H5OH) have the same molecular formula but differ in their connectivity, which explains their difference in volatility. Dimethyl ether does not have hydrogen bonding because it lacks an -OH group, so its primary intermolecular forces are London dispersion forces. On the other hand, ethyl alcohol can form hydrogen bonds due to the presence of an -OH group, leading to much stronger intermolecular forces.

Consequently, at a given temperature, more dimethyl ether molecules will escape into the vapor phase than ethyl alcohol molecules, making dimethyl ether more volatile and giving it a higher vapor pressure than ethyl alcohol. This explanation is consistent with the general understanding that molecules with hydrogen bonding usually have higher boiling points and lower volatility compared to those that cannot engage in hydrogen bonding.