Solubility

 Define: miscible, saturated, unsaturated, solubility, supersaturation.
 Describe factors that effect solubility.
 Use “solubility rules” to predict the solubility of an ionic compound in water.
 Interpret and construct solubility curves.
Use solubility curves to distinguish among saturated, supersaturated, and unsaturated
solutions.
 Apply the “like dissolves like” rule to real-world situations.

Materials: Salt, Alcohol, Water, Test Tubes, Test Tube Rack
Essential Questions:
1.What are the factors that
affect solubility?
2.How do we use “solubility
rules” to predict the solubility
of an ionic compound in
water? Explain.
3.What does a solubility curve
show and how do we use it?
Aim:
How can we
predict the
solubility of a
solute in a
solvent?
Key Words:
miscible, saturated,
unsaturated, solubility,
supersaturation
Do Now
Reference Table F was used to identify the precipitate in doublereplacement reactions (see notes from previous week).
Use the solubility rules in Table F to classify each of the five
compounds given below as soluble or insoluble.
(a) NaNO3
_____________________
(b) BaSO4
_____________________
(c) (NH4)2S
_____________________
(d)AgI
_____________________
NaNO3 _____________________
BaSO4
_____________________
(NH4)2S _____________________
AgI
_____________________
Answers
(a) NaNO3
(b) BaSO4
(c) (NH4)2S
(d) AgI
Soluble
insoluble
soluble
insoluble
Salt/Alcohol + Water Demo
1) Why won’t the salt dissolve after a certain amount has
been added?
2) What do we call this point?
3) What do we call it before we reach this point?
4) How can we get a supersaturated solution?
5) Does the same phenomenon occur between alcohol and
water?
6) What can we call a solution between alcohol and water?
Notes
I. Solubility
A. Definitions
1. Saturated Solution - a solution where the
solvent can no longer dissolve more solute at
a certain temperature
2. Unsaturated Solution - a solution that has not
yet reached its saturation point.
3. Supersaturated Solution – a solution which
holds more solute that can be dissolved at a
certain temperature
Notes
4. Soluble – a substance that can form
fairly concentrated solutions
5. Miscible – a solution that can be mixed
in all proportions of solutes to solvent
without hitting a saturation point. Most
liquid-liquid solutions and all gas-gas
solutions are miscible.
6. Insoluble – A substance that can form
only very dilute solutions.
How can we define
solubility?
Notes
7. Solubility - the ability and quantity
of solute needed to saturate a
given amount of solvent.
a. The unit used to designate this number is grams
of solute per 100 grams of solvent.
Ex. at 53 C, 85 grams of KNO3 will saturate 100
grams of H2O. Therefore, the solubility of KNO3
at 50 C is reported as: 85 grams KNO3 per 100
grams H2O.
Solubility Curves
Answer the following questions based
on the solubility chart on the left
1. What is the maximum amount in
grams of hydrochloric acid that can
dissolve in 100 g of water in 80 C?
How about in 40 C?
____________
____________
2. What is the maximum amount in
grams of salt that can dissolve in 100
ml of water in 80 C? How about in 40
C?
____________
____________
Notes
B. Solubility Chart
(Reference Table G)
1. Solubility curves show
the concentration of
a saturated solution
at varying
temperatures.
Thought Questions
Based on the solubility curve in the previous slide, we
can see that solubility increases with increasing
temperature.
A. How can you explain 3 curves on the table which
show that solubility decreases with increasing
temperature?
B. What do you predict will happen if I prepare a
solution to saturation at a high temperature and
then slowly decrease the temperature?
Notes
C. The solubility of a gas in water decreases
as the temperature increases.
Ex: HCl (aq) SO2 (aq)
D. Supersaturated Solution – Usually, when a
solution is prepared at a higher
temperature and then cooled slowly, the
solute is still suspended in the solution in an
unstable way.
Ex. Honey – After a period of time, the excess sugar in
honey will crystallize at the bottom of the jar. The
honey can be restored to its original supersaturated
state by heating it and then allowing it to cool slowly
What Are Some Factors
that Effect Solubility
Hint: Think about why your soda
needs to be chilled or coffee needs
to be heated.
Notes
E. Factors that affect solubility
1. Temperature
2. Nature of Solute & Solvent
3. If the solute is a gas: Atmospheric
Pressure
Learning Check
Use reference table G to answer the following questions:
1) A solution containing 95 grams of KNO3 dissolved
in 100 grams of water at 55 C is classified as being
a. saturated
b. unsaturated
c. supersaturated
d. ultrasaturated
2) What is the maximum number of grams of NH4Cl
that will dissolve in 200 grams of water at 70 C?
a. 62
b. 124
c. 70
d. 226
Learning Check
3) Approximately how many grams of KClO3 are
needed to saturate 100 grams of H2O at 40 C?
a. 6
b. 14
c. 37
d. 47
4) Which of the following is most soluble at 60
C?
a. NH4Cl
b. NaNO3
c. KNO3
d. KI
5) Which saturated solution is the most
concentrated at 20 C?
a. NaCl
b. KClO3
c. KI
d. KNO3
Notes
Solubility
I. Solubility
A. Definitions
1. Saturated Solution - a solution where the solvent
can no longer dissolve more solute.
2. Unsaturated Solution - a solution that has not
yet reached is saturation point.
3. Supersaturated Solution - Occasionally, when a
solution is prepared at a higher temperature and
then cooled slowly, the solute is still suspended
in the solution in an unstable way.
Ex. Honey – After a period of time, the excess
sugar in honey will crystallize at the bottom
of the jar. The honey can be restored to its
original supersaturated state by heating it and
then allowing it to cool slowly
4. Miscible – a solution that can be mixed in all proportions of
solutes to solvent without hitting a saturation point. Most
liquid-liquid solutions and all gas-gas solutions are
miscible.
5. Soluble – a substance that can form fairly concentrated
solutions
6. Insoluble – A substance that can form only very dilute
solutions,
7. Solubility of Solute-Solvent Pair - the quantity of solute
needed to saturate a given amount of solvent.
8. The unit used to designate this number is grams of solute
per 100 grams of solvent.
Ex. at 53 C, 85 grams of KNO3 will saturate 100 grams of
H2O. Therefore, the solubility of KNO3 at 50 C is
reported as: 85 grams KNO3 per 100 grams H2O.
B. Factors that affect solubility
1. Temperature
2. Nature of Solute & Solvent
3. If the solute is a gas: Atmospheric Pressure
C. Solubility Chart (Reference Table G)
1. Solubility curves show the composition of a
saturated solution at varying temperatures.