LAB 10: SOLUBILITY:
SOLUBILITY RELATIONSHIPS OF SALTS AND GASES
PURPOSE: To observe and describe with net ionic equations the formation of insoluble salts.
To measure the solubility of KNO3 at various temperatures and graph a solubility
curve.
To derive from experiment the relationships between Pressure (P), Temperature
(T), and Water Solubility of gases.
SAFETY CONCERNS:
Always wear safety goggles.
Handle and dispose of broken glass safely.
SOLUBILITY:
Soluble and Insoluble Salts:
Although many ionic compounds (salts) dissolve in water (are soluble) there are some that do
not. These are known as insoluble salts. A slurry of the insoluble salt barium sulfate (BaSO4) is
often used in medicine as an opaque substance to help outline the gastrointestinal tract in x-ray
images.
The solubility of ionic compounds can be predicted by using the simple rules given in the
following tables:
Solubility Rules for Ionic Compounds:
Soluble in Water
Any salt with
Li1+,
NH41+,
1+
Na ,
NO311+
K ,
C2H3O21Most Chlorides,
Cl1Most Sulfates,
SO42-
Insoluble in Water
 Except
Except 
Salts with
OH1-,
CO32-,
S2-,
3PO4
AgCl,
Hg2Cl2, PbCl2,
CaSO4
SrSO4
BaSO4,
Except 
PbSO4
Table of Common Solubilities:
1+
Li
Na1+
K1+
NH41+
Ca2+
Sr2+
Ba2+
Pb2+
Ag1+
Hg1+
NO31S
S
S
S
S
S
S
S
S
S
C2H3O21S
S
S
S
S
S
S
S
S
S
Cl1S
S
S
S
S
S
S
I
I
I
SO42S
S
S
S
I
I
I
I
S
S
OH1S
S
S
S
I
I
I
I
I
I
CH104 Lab 10: Solubility (F15)
CO32S
S
S
S
I
I
I
I
I
I
S2S
S
S
S
I
I
I
I
I
I
PO43S
S
S
S
I
I
I
I
I
I
127
When solutions of two soluble ionic compounds are mixed, the formation of an insoluble solid
precipitate indicates that a chemical reaction has occurred. A solid forms when the positive ion
of one substance in solution, and the negative ion in solution are more attractive to each other
than they are to water. For example, mixing solutions of the soluble salts NaCl(aq) and AgNO3(aq)
will produce a white solid, which is the insoluble salt AgCl(s).
NaCl(aq) + AgNO3(aq)
Soluble Salts

AgCl(s)
+
NaNO3(aq)
Insoluble Salt
Total Ionic Equation: (Shows all ions present)
Na1+(aq)
+ Cl1-(aq) + Ag1+(aq) + NO31-(aq)  AgCl(s) + Na1+(aq) + NO31-(aq)
Net Ionic Equation: (Shows only the reaction that has occurred)
Ag1+(aq) + Cl1-(aq)  AgCl(s)
Solubility Values:
The solubility (ability to dissolve) of a solid in a liquid depends upon the
 polarity of the solute and solvent (like dissolves like),
 temperature, (Generally, the dissolving of a solid solute is endothermic, which means that solubility

increases with an increase in temperature. So most solids are more soluble (S) as T where gases are less
soluble (S) as T),
pressure (most solids and liquids are not affected by pressure but gases are more soluble (S) as P)
A solution that holds the maximum amount of solute possible at a certain temperature it is said to
be saturated. When more solute is added to a saturated solution the excess appears as a solid in
the container. The maximum amount of solute that dissolves in a particular solvent is called the
solubility. Solubility is usually stated as the number of grams of solute that dissolve in 100 mL (
or 100g) of water.
Solubility =
g solute
or =
g solute
100 mL water
100 g water
Solubility of Gases:
Gases, like some solids or liquids, are able to dissolve partially in water. Some gases, such as
Oxygen (O2), Nitrogen (N2), or Carbon Dioxide (CO2) easily dissolve in water. We say these
are soluble gases. However, some gases such as Helium (He) dissolve only a little bit. Gases
that do not dissolve in water very much are said to be either insoluble or partially soluble
depending on just how much does dissolve.
Unlike the solubility of solids or liquids, the ability of gases to dissolve in water (the solubility
of gases) changes if either the surrounding pressure or the surrounding temperature changes.
In the laboratory exercises that follow you will discover the relationships between Pressure (P),
Temperature (T) and the Solubility of a gas, and be able to derive Henry’s Law for yourself.
128
CH104 Lab 10: Solubility (F15)
NOTES:
PROCEDURES:
ACTIONS:
1
4. Make mixtures by adding 3 drops of the following solutions
to those already in the wells. Observe any insoluble salts
formed and report your observations. (Column I3.)
1. To the AgNO3, add sodium chloride, NaCl.
2. To the AgNO3, add sodium sulfate, Na2SO4.
3. To the AgNO3, add sodium hydroxide, NaOH.
4. To the AgNO3, add sodium carbonate, Na2CO3.
5. To the AgNO3, add sodium phosphate, Na3PO4.
6. To the Ba(NO3)2, add sodium chloride, NaCl.
7. To the Ba(NO3)2, add sodium sulfate, Na2SO4.
8. To the Ba(NO3)2, add sodium hydroxide, NaOH.
9. To the Ba(NO3)2, add sodium carbonate, Na2CO3.
10. To the Ba(NO3)2, add sodium phosphate, Na3PO4.
11. To the CaCl2, add sodium chloride, NaCl.
12. To the CaCl2, add sodium sulfate, Na2SO4.
13. To the CaCl2, add sodium hydroxide, NaOH
14. To the CaCl2, add sodium carbonate, Na2CO3.
15. To the CaCl2, add sodium phosphate, Na3PO4.
3
Pattern of spot plate wells:
AgNO3
1
Ba(NO3) 2 CaCl2
6
11
NaCl
O O O
2
Na2SO4
3. Choose a pattern of wells on your spot plate similar to that
shown3 and place drops of the following solutions:
 Into the 1st column of 5 wells place 3 drops of silver
nitrate, AgNO3, solution.
 Into the 2nd column of 5 wells place 3 drops of barium
nitrate, Ba(NO3)2, solution.
 Into the 3rd column of 5 wells place 3 drops of calcium
chloride, CaCl2, solution.
In the absence of a
transparent spot plate a
transparent plastic sheet can
be used. Place it on a nonwhite background so that the
formation of any white solid
precipitate will be visible.
7
12
O O O
3
8
13
O O O
NaOH
2. Obtain a transparent spot plate and place it over a dark or
colored background. 2
2
Na2CO3
1. Obtain dropper bottles of 0.1 M aqueous solutions1 of
NaCl, Na2SO4, Ba(NO3)2, AgNO3, Na3PO4, CaCl2, NaOH,
and Na2CO3.
4
9
14
O O O
5
Na3PO4
I. SOLUBLE & INSOLUBLE SALTS:
Verify, using the solubility
tables, that these compounds
are indeed soluble in water.
10
15
O O O
5. Write the ions that are present in each of the two solutions
mixed in each reaction (Column I2.).
6. Using the solubility rules, draw a circle around the ions that
would form an insoluble salt.
7. For any chemical reactions that took place write the net ionic
equations (Column I4) showing the correct formulas for any
insoluble salts formed. Use the symbols (aq) and (s) for
those ions or compounds that are aqueous or solid.
CH104 Lab 10: Solubility (F15)
129
II. SOLUBILITY OF POTASSIUM NITRATE, KNO3:
The temperature at which KNO3 is soluble is determined by heating
and cooling a KNO3 solution.
1. Weigh out a portion4 of solid potassium nitrate, KNO3, as
instructed5 on a tared weighing paper or tared container.
2. Report the mass of the potassium nitrate you weighed to the
accuracy of your balance.
3. Place 5.0 mL of water in a large test tube and add your weighed
amount of KNO3.
4. Clamp the test tube of KNO3 to a ring stand and place the test
tube in a beaker of water. Use a hot plate or Bunsen burner to
heat the water. 6 Stir the mixture and continue heating until all
the KNO3 dissolves.
4
To reduce the amount of
KNO3 used, each group of
students will be assigned to
weigh out an amount of KNO3
from 2 to 7 grams. The results
will be shared with the class.
5
Weigh out an amount of
KNO3 that is close to your
assigned amount. It does not
have to be exact. For example,
if you are assigned an amount
of 3 grams, measure out a
mass such as 3.10 g or 3.25 g
or 2.85 g. It is not necessary
to add or remove KNO3 to
obtain exactly 3.00 g. Weigh
carefully and record the actual
mass of your sample to the
accuracy of your balance.
6
Heating the solution.
5. As soon as all the KNO3 dissolves, turn off the burner or hot
plate. Loosen the clamp and remove the test tube from the hot
water. As the test tube and contents cool, stir gently7 with a
thermometer. Look closely for the first appearance of crystals.
As soon as you see some solid crystals, read and record the
temperature of the solution. 8
6. Place the test tube back into the hot water bath and begin
heating again. Repeat the warming and cooling of the solution
until you have obtained three or more temperature readings
that closely agree.
7. Set the test tube aside. In 15-20 minutes, observe the
appearance of the crystals in the test tube.
8. To discard, add water and heat until the KNO3 dissolves. Pour
the solution in proper waste container.
9. From your data, express the solubility of KNO3. in g’s per 100
mL water. 9
10. Collect the solubility data obtained by other members of the
class from other sample sizes.
11. On the same grid where you reproduced the text book solubility
curve for KNO3 create another curve using the class solubility
data. (Plot solubility (g KNO3/100 mL water) on the vertical axis (Y) and
the temperature (0-100oC) on the horizontal axis (X).) Distinguish the 2
curves using different colors or symbols or line styles.
130
CH104 Lab 10: Solubility (F15)
7
Without gentle stirring there
is a chance of “super cooling”
where a temporarily
supersaturated solution forms.
If this happens crystals may
not precipitate until a lower
temperature than expected.
8
This is the temperature at
which the solution becomes
saturated. The amount of
KNO3 in that solution is the
solubility of KNO3 at that
temperature.
9
Solubility is expressed as the
number of grams of solute in
100 mL of water. Because
you used a sample of 5.0 mL
of water, the mass of the solute
you measured out and the 5.0
mL of water are both
multiplied by 20.
g KNO3 x 20 = g KNO3
20 100 mL H2O
5.0 mL H2O
PROCEDURES:
10
ACTIONS:
III. HENRY’S LAW: SOLUBILITY VS PRESSURE
8. Pour ice cold10 carbonated water (CO2 dissolved in H2O)
into a vacuum flask to a level of about 1 inch.
9. Set the tightly stoppered flask in an ice water bath to keep
it cold.
10.
Connect the flask to the vacuum source and turn it on full
force.
On the report sheet (IIIA) record your
observations. Indicate increasing solubility (Ability of gas
to dissolve) (S) of CO2 gas with up arrows, and
decreasing solubility (S) of CO2 gas with down arrows.
11. Detach the vacuum tubing from the source to allow the
flask to return to atmospheric pressure. Record your
observations. (IIIB)
12. Formulate Henry’s Law by summarizing your results in
the space provided on the report sheet. (IIIE)
PHYSIOLOGICAL APPLICATION: THE BENDS
13. Now that you have discovered Henry’s law, imagine what
would happen to the solubility (S) of air (oxygen and
nitrogen gases) in the blood (a water solution) of a diver
that descends to the depths of the ocean (P)11 Record
your hypothetical results (IIIC).
We keep the solution cold
because we want to look at only
one condition at a time. We are
now looking at the effects of
pressure on the solubility of the
CO2. Temperature also affects
solubility of gases in water, so to
change the temperature changes
the experiment.
11
At the atmospheric pressure of
sea level we all have a certain
amount of Oxygen (O2) and
Nitrogen (N2) gases dissolved in
our blood. When a scuba diver
descends to the bottom of the
ocean there is a greater amount
of atmosphere, including water,
pressing down.
12
When a diver ascends too
quickly from a high pressure
atmosphere under the ocean, to a
low pressure atmosphere at sea
level, the change in solubility of
the blood gases occurs too
rapidly.
Imagine that the
carbonated beverage in step IV3
is blood containing dissolved air
and that putting it under reduced
pressure is similar to the diver
rising quickly from the depths of
the ocean to the surface.
Bubbles in the blood, joints, and
muscles cause the diver to bend
over in pain with “the bends”.
14. Now imagine that the diver in the depths of the ocean
quickly rises to the surface. What happens to the
atmospheric pressure and what happens to the solubility
of gases in the blood? 12 Record your hypothetical results
(IIID)
CH104 Lab 10: Solubility (F15)
131
IV. SOLUBILITY VS TEMPERATURE
As you follow the instructions given in this section you will answer the given question by
practicing the scientific method. Use the example given in the discussion section at the
beginning of the Burners and Flames lab chapter to help you. The question we’ll tackle is:
What is the relationship between the solubility of a gas and the
temperature of the liquid in which it is dissolved?
1. On the report sheet (IVA) make an educated guess, or
hypothesis, to answer the question. Explain why
you came up with the hypothesis you did based on
what you have learned so far or past experiences.
2. Create experimental procedures (IVB/C) to test
your hypothesis.13
3. Perform your experiment and record the results14 on
the report sheet (IVD).
4. Write a conclusion statement (IVE) that sums up
the answer to the original question giving factual
evidence from your experiment to support your
answer.
5. Analyze any potential for errors, and record (IVF)
any hints to achieving reliable results.
PRACTICAL OR PHYSIOLOGICAL APPLICATION:
6. Report a practical application or a physiological
application where this relationship between gas
solubility and temperature might be important. (IVG)
132
CH104 Lab 10: Solubility (F15)
13
Your experimental procedures must
be clear enough to be followed by
another person. Be clear about what
results to look for.
Depending on the type of experiment
you choose, you may need to include
a “control” experiment so that you
are confident that you are seeing
solubility
and
temperature
relationships and not just water
boiling.
14
Be sure that you are correct in the
description of your results.
For
example, if your experiment requires
you to look for bubbles escaping are
you sure that the gas bubbles you
see are dissolved gases escaping or
are you just seeing water boil?
LAB 10: SOLUBILITY
NAME_____________
PRE LAB EXERCISES:
DATE______________
1. ___An insoluble salt is _____
A. an ionic compound that dissolves in water at room temperature.
B. an ionic compound that does not dissolve in water at room temperature.
C. a covalent compound that dissolves in water at room temperature.
D. a covalent compound that does not dissolve in water at room temperature.
2. ___The correct name(s) for the formula PbSO4 is(are)
A. Plumbous Sulfate
B. Plumbic Sulfate
C. Lead Sulfate
3. ___The correct formula for Calcium Nitrate is
A. CaNO3
B. Ca(NO3) 2
C. Ca2NO3
D. Lead (I) Sulfate
D. Ca3N2
E. Ca(NO2)2
4. ___Which of the following is true about the solubility of substances in water?
A. Atmospheric pressure has no effect on the quantity of any substances that will dissolve in
water.
B. Atmospheric pressure has a large effect on the quantity of a solid that will dissolve in water.
C. Atmospheric pressure has a large effect on the quantity of a liquid that will dissolve in water.
D. Atmospheric pressure has a large effect on the quantity of a gas that will dissolve in water.
E. More than one of these is correct.
5. A. Write a balanced chemical equation for the reaction between silver nitrate and sodium
carbonate. Use symbols (aq) and (s) to indicate aqueous and solid components of the equation.
B. Write the balanced ionic equations for the reaction between silver nitrate and sodium carbonate.
Use symbols (aq) and (s) to indicate aqueous and solid components of the equation.
Total ionic equation
Net ionic equation
6. On the grid in part II of your report sheet reproduce the theoretical solubility curve for KNO3 using
the graphed data from the solubility curve in your text.
7. What effect would “super cooling” have on the solubility of KNO3? How can you prevent it?
CH104 Lab 10: Solubility (F15)
133
134
CH104 Lab 10: Solubility (F15)
LAB 10: SOLUBILITY
NAME___________________
REPORT:
PARTNER_________DATE___
I. SOLUBLE AND INSOLUBLE SALTS
1. Compounds in
Mixture
2. Ions present in 3. Observations
mixture
4. Write the balanced net ionic equation
(if none put NR)
1.
Ag1+
NO31-
AgNO3(aq) + NaCl(aq)
Net ionic equation
1+
Na
2.
AgNO3(aq) + Na2SO4(aq)
3.
AgNO3(aq) + NaOH(aq)
4.
AgNO3(aq) + Na2CO3(aq)
5.
AgNO3(aq) + Na3PO4(aq))
6.
Ba(NO3)2(aq) + NaCl(aq)
Observations
1-
Cl
Observations
Net ionic equation
Observations
Net ionic equation
Observations
Net ionic equation
Observations
Net ionic equation
Observations
Net ionic equation
7.
Observations
Ba(NO3)2(aq) + Na2SO4(aq)
Net ionic equation
8.
Observations
Ba(NO3)2(aq) + NaOH (aq)
Net ionic equation
CH104 Lab 10: Solubility (F15)
135
1. Compounds in
Mixture
2. Ions present in 3. Observations
mixture
4. Write the balanced net ionic equation
(if none put NR)
9.
Observations
Ba(NO3)2(aq) + Na2CO3(aq)
Net ionic equation
10.
Observations
Ba(NO3)2(aq) + Na3PO4(aq)
Net ionic equation
11.
Observations
CaCl2(aq) + NaCl(aq)
Net ionic equation
12.
Observations
CaCl2(aq) + Na2SO4(aq)
Net ionic equation
13.
Observations
CaCl2(aq) + NaOH(aq)
Net ionic equation
14.
Observations
CaCl2(aq) + Na2CO3(aq)
Net ionic equation
15.
Observations
CaCl2(aq) + Na3PO4(aq)
Net ionic equation
Summary & Conclusions:
Complete the following solubility table using Theoretical value (THR) and
your own Experimental (EXP) results. Use S for soluble, and I for insoluble. Circle any unexpected results:
NO31THR
1+
Na
Ca2+
Ba2+
Ag1+
S
S
S
S
EXP
Cl1THR
S
EXP
SO42THR
EXP
S
Explanation/Analysis: Were your results as expected?
136
OH1THR
EXP
S
Explain specifics.
CH104 Lab 10: Solubility (F15)
CO32THR
S
EXP
PO43THR
S
EXP
II. SOLUBILITY OF KNO3:
Group Names:
Circle your own
Actual Mass KNO3 used
Temperature
Solubility
(crystals appear)
( g KNO3/100 mL H2O)
2g.
3g.
3.5g.
4g.
4.5g
5g.
5.5g
6g.
6.5g
7g.
Solubility Curve for KNO3
Solubility ( g KNO3/100 mL H2O)
200
150
100
50
0
0
25
50
Temperature (oC)
75
100
Summary:
1.___ The solubility of KNO3 in water _____ as the temperature increases.
A. decreases
B. increases,
C. does not change
Explanation/Analysis: How does your solubility curve compare to that of KNO3 presented in your textbook?
CH104 Lab 10: Solubility (F15)
Explain.
137
III. HENRY’S LAW: SOLUBILITY VS PRESSURE
Action
Observations
Effect on
Pressure
P or P
Effect on
gas
Solubility
S or S
A. Vacuum source turned on
with carbonated solution in
flask.
B. Vacuum hose detached
with carbonated solution in
flask.
C. A diver is deep in the
ocean with gases dissolved in
the blood
D. A diver, deep in the ocean
with gases dissolved in the
blood, comes rapidly to the
surface.
Imagine what you would see.
Imagine what you would see.
E. Conclusion:
1.___ The solubility of a gas in water (the ability of a gas to dissolve) _____ as the pressure _____.
A. decreases, increases
B. increases, increases.
C. does not change, changes
2.___ Henry’s Law: The solubility of a gas ____________ the pressure.
A. varies directly with
B. varies inversely with
C. is unrelated to
Explanation/Analysis: Were your results as expected?
138
Explain specifics.
CH104 Lab 10: Solubility (F15)
IV. SOLUBILITY VS TEMPERATURE
QUESTION:
What is the relationship between the solubility of a gas (the ability of a gas to
dissolve in water) and the temperature of the solvent in which it is dissolved?
A. Hypothesis: (Do before any experiment is done. Use complete sentences; give rationale based on previous information.)
I believe that as the temperature of a liquid increases the solubility of dissolved gases will _______.
I believe this because ………………
B. Experimental Procedure: (Give details that others could follow; include instructions for what to look for and how to
determine if your experiment is accomplishing your goal.)
1.
2.
3.
4.
C. Experimental Control: If your experiment requires you to look for bubbles escaping how will you insure that the gas bubbles you see are
dissolved gases escaping and not just water boiling? If your experiment requires you to look for gases filling a balloon how will you insure that the
inflation of a balloon is from dissolved gases escaping and not just hot gases expanding (Charles Law)?
D. Results:
Action
Observations
Effect on
Temperature
T or T
Effect on gas
Solubility
S or S
E. Summary/Conclusion:
1.___
The solubility of a gas in water (the ability of a gas to dissolve) ___ as the temperature ___.
A. decreases, increases
B. increases, increases.
2.___
The solubility of a gas ____________ the temperature.
A. varies directly with
B. varies inversely with
3.___
C. is unrelated to
My original hypothesis was___
A. totally incorrect.
B. correct as written.
C. correct with the following revisions:______________________________________
F. Explanation/Analysis: (Give warnings or advice for modifications to your experiment.
Give potential for errors. Explain)
G. Practical or Physiological Application: (Where might this temperature/solubility relationship be observed in nature, health, or
everyday life?)
CH104 Lab 10: Solubility (F15)
139
LAB 10: SOLUBILITY
NAME____________
RELATED EXERCISES:
1.___
Gas being evolved when the cap is removed from a cola drink illustrates
B. Boyle’s Law
C. Charles’s Law
H. Henry’s Law
N. None of these
2.___
Which of the following portions of today’s laboratory experiments most illustrates the “bends”?
A. The precipitation of an insoluble salt at atmospheric pressure.
B. The variation of solubility of KNO3 with temperature.
C. The variation of solubility of CO2 with pressure.
D. The variation of solubility of CO2 with temperature.
N. None of these
3.___
When sea divers who are suffering from the “bends” are transported to the hospital pressure
chamber which of the following would be most advisable?
A. Apply ice packs to the diver.
B. Apply heat packs to the diver.
4.___
When an airplane suddenly looses cabin pressure the pilot will quickly decrease the altitude
because decreasing the altitude will ____________
A. increase the temperature and thus prevent the bends.
B. decrease the temperature and thus prevent the bends.
C. decrease the pressure and thus prevent the bends.
D. increase the pressure and thus prevent the bends.
E. give the passengers less distance to fall when they have to jump out of the plane.
5.
A. The solubility of sucrose (common table sugar) at 70oC is 320 g/100 g H2O. How much sucrose
(a common carbohydrate) can possibly dissolve in a cup of tea (about 240 g of water) at 70oC?
(Show calculations and circle your answer.)
B. How many Food Calories (kcals) would the cup of tea in part A provide? (Show calculations and
circle your answer.)
C. A can containing 355 mL of soft drink contains 42 g sugar (sucrose). How many Food
calories would come from drinking this soda? (Show calculations and circle your answer.)
REFERENCE SEARCH:
6. A. Solubility is not an all or nothing concept but rather every substance has degrees of solubility. Substances in which a
“high” number of grams will dissolve in 100 mLs water are labeled soluble (S). Substances in which a “low” number of
grams will dissolve in 100 mLs water are labeled insoluble (I).
Use the CRC Handbook to look up solubility data that would complete the table. Record the solubility
and label S or I.
2+
Ca
Solubility of Selected Salts (g/100 mL) in cold water
NO31Cl1SO42OH1CO32121.2 = S
PO43-
B. How does the CRC solubility information compare to your results in Part I? At what point do you think
compounds are considered to be soluble or insoluble? Explain
140
CH104 Lab 10: Solubility (F15)