Question

evaporation rate
various compounds
the data below shows the change in
temperature when 4 compounds are
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 like
cause for the difference in the rate of
evaporation for compounds a and b?

the atoms have different types of bonds holdir
the molecule together.

the molecules have different numbers of oxyge
atoms.

the molecules have different types of dipole-
dipole forces.

the molecules have different amounts of
dispersion forces.

Explanation:

Evaporation rate relates to intermolecular forces (IMFs): weaker IMFs mean faster evaporation (more temperature drop). Compounds A and B only have dispersion forces (DF). Dispersion forces depend on molecular size/molar mass—larger molecules have stronger DF, slower evaporation. A has a bigger temperature drop (faster evaporation) than B, so A has weaker DF than B, meaning different amounts of dispersion forces.

Answer:

The molecules have different amounts of dispersion forces.