Question

exposed to room temperature air over 2 minutes.
compare the data for compounds a and b only to answer the question.

compound	temperature change (°c)	type of imf
b	-9.2	df
c	-7.6	df, dd
d	-4.8	df, dd, hb

df – dispersion forces, dd – dipole - dipole, hb – hydrogen bonding

which of the following is the most likely cause for the difference in the rate of evaporation for compounds a and b?

• the molecules have different amounts of dispersion forces.
• the atoms have different types of bonds holding the molecule together.
• the molecules have different types of dipole - dipole forces.
• the molecules have different numbers of oxy atoms.

Explanation:

Evaporation rate depends on intermolecular forces (IMFs). Compounds A and B both have only dispersion forces (DF) as their IMF. A larger temperature drop means faster evaporation (weaker IMFs). Since their IMF type is the same, the difference in evaporation rate must come from different strengths of dispersion forces (e.g., due to different molecular sizes/masses affecting DF strength).

Answer:

The molecules have different amounts of dispersion forces.