CHEMISTRY 11 AP – “LIKE DISSOLVES LIKE” WORKSHEET
1) A dry cleaner observes that a stain on a piece of clothing dissolves in water but not in
tetrachloroethene. Consider the following diagram of the structure of tetrachloroethene.
(a) What types of intermolecular forces exist in water? In
tetrachloroethene?
Water contains hydrogen bonds, dipole-dipole bonds and London
dispersion forces. Tetrachloroethene contains only London
dispersion forces.
(b) Explain why the stain did not dissolve in tetrachloroethene.
Since the stain was not removed by the tetrachloroethene, the weaker London dispersion forces
present in tetrachloroethene must not have been strong enough to separate the IMFs present
between the molecules of the stain
(c) Explain why you cannot narrow down the solute bond type to just one type.
Since both ionic and polar solutes are soluble in water, you would not be able to classify the
bond type to either ionic or polar. Both ionic and polar solutes possess equally strong IMFs and
are therefore able to separate the IMFs present in a polar solvent and form a solution.
2) Is Br2 (l) more soluble in CS2 (l) or NH3 (l)? Explain.
Br2 (l) is non-polar therefore it is more soluble in CS2, which is also non-polar. The only IMFs
present are London dispersion forces therefore the similar strength IMFs will be able to separate
each other and produce a solution. Since NH3 (l) is polar, there are much stronger IMFs present
(hydrogen bonds) therefore the weaker London dispersion forces would not be able to separate the
hydrogen bonds between NH3 (l).
3) Explain why NH3 (l) is very soluble in water, but NCl3 (l) is not.
NH3 (l) is polar, just like water, therefore the equally strong IMFs present in both molecules will be
able to separate each other and produce a solution. NCl3 (l) is non-polar so will not dissolve in water.
The weaker London dispersion forces present in NCl3 (l) would not be able to separate the hydrogen
bonds between H2O.
4) When I2 is added to water, it does not dissolve. However, if I2 is added to an aqueous solution of KI,
it will dissolve. Use the following reaction, and your understanding of IMFs to explain the above
observations.
I2 (s) + I- (aq) → I3- (aq)
I2 is non-polar, so will not dissolve in polar water. If the water contains I- (aq) ions however, the I2 (s)
reacts to form I3- (aq) which is ionic. This ion will then be attracted to the positive dipole on the
hydrogen atoms on the water molecules.
5) Which is more soluble in water? Explain.
(a) C4H10 or C3H6OH
C3H6OH since it contains a polar end (the –OH group) it is attracted to the polar water
molecules.
(b) MgCl2 or toluene (C7H8)
MgCl2 is ionic so will dissolve better in water since the positive poles of the water molecule will
be attracted to the negative Cl- ion while the negative poles of the water molecule will be
attracted to the positive Mg2+ ion. Toluene is non-polar.
6) Glycerin (shown to the right) is a common solvent and is found in many
skin care products. A student mixes 10 mL of water, 10 mL of glycerin
and 10 mL of carbon tetrachloride together. A small amount of CuCl2
was added to the mixture. Explain what you would see.
The glycerin and water would mix together since both glycerin and
water are polar, but the carbon tetrachloride would remain as a separate
layer since it is non-polar. The CuCl2 would dissolve into the
water/glycerin layer and would colour that layer blue.
7) Ethylene glycol (shown to the left) is commonly used as antifreeze.
Circle the solvent in which it would be most soluble in each pair below.
(a) Water or paint thinner (a non-polar covalent solvent)
(b) Ammonia or carbon tetrachloride
(c) Benzene or glycerin.
Ethylene glycol, water, ammonia and glycerin are all polar molecules and therefore share similar
strength IMFs.
8) List the IMFs present between the following solutes and solvents:
(a) CsCl in H2O
CsCl is ionic. Water contains hydrogen bonds, dipole-dipole bonds and London dispersion
forces.
(b) CH3OH in glycerin
CH3OH is polar and contains hydrogen bonds, dipole-dipole forces and London dispersion
forces. Glycerin is polar and contains hydrogen bonds, dipole-dipole forces and London
dispersion forces.
(c) N2 in C8H18
N2 contains only London dispersion forces as does C8H18 since they are both non-polar.
(d) Acetone
in ammonia
Acetone contains dipole-dipole forces and London dispersion forces. Ammonia contains
hydrogen bonds, dipole-dipole forces and London dispersion forces.