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Chapter 12 Lecture
Basic Chemistry
Fourth Edition
Chapter 12
Solutions
12.3 Solubility
Learning Goal Define solubility;
distinguish between an unsaturated and
a saturated solution. Identify a salt as
soluble or insoluble.
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Solubility
Solubility
• is the maximum amount of solute that
dissolves in a specific amount of solvent
• can be expressed as grams of solute per
100 grams of solvent, usually water
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Saturated Solutions
Saturated Solutions
• contain the maximum amount of solute that can
dissolve
• have undissolved solute at the bottom of the
container
• have equal rates at which the solute dissolves
and crystallizes
Solute dissolves
Solute + Solvent
Saturated Solution
Solute recrystallizes
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Saturated, Unsaturated Solutions
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Solubility and Temperature
Solubility
• depends on temperature
• increases as temperature
increases for most solids
• decreases as temperature
increases for gases
In water, most common solids
are more soluble as the
temperature increases.
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Learning Check
At 40 C, the solubility of KBr is 80. g/100 g H2O.
Identify the following solutions as either
(S) saturated or (Un) unsaturated.
A. 60. g of KBr added to 100. g of water at 40 C
B. 200. g of KBr added to 200. g of water at 40 C
C. 25 g of KBr added to 50. g of water at 40 C
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Solution
At 40 C, the solubility of KBr is 80. g/100 g H2O.
A. 60. g of KBr added to 100. g of water at 40 C
Un, the amount of 60. g of KBr in 100. g of water, is
less than the solubility of 80. g of KBr in 100. g of
water.
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Solution
At 40 C, the solubility of KBr is 80. g/100 g H2O.
B. 200. g of KBr added to 200. g of water at 40 C
S, in 100. g of water, 100. g of KBr exceeds the
solubility of 80. g of KBr water at 40 C.
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Solution
At 40 C, the solubility of KBr is 80. g/100 g H2O.
C. 25 g of KBr added to 50. g of water at 40 C
Un, this is the same as 50. g of KBr in 100. g
of water, which is less than the solubility of
80. g of KBr in 100 g of water at 40 C.
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Solubility and Pressure
Henry’s law states that
• the solubility of a gas in a liquid is directly
related to the pressure of that gas above the
liquid
• at higher pressures, more gas molecules
dissolve in the liquid
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Solubility and Pressure, Henry’s Law
When the pressure of a gas above the solution
decreases, the solubility of that gas in the
solution also decreases.
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Learning Check
A. Why could a bottle of carbonated drink
possibly burst (explode) when it is left out in
the hot sun?
A. Why do fish die in water that is too warm?
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Solution
A. Why could a bottle of carbonated drink
possibly burst (explode) when it is left out in
the hot sun?
The pressure in a bottle increases as the gas leaves
solution, because it becomes less soluble at high
temperatures. As pressure increases, the bottle
could burst.
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Solution
B. Why do fish die in water that is too warm?
Because O2 gas is less soluble in warm water, fish
cannot obtain the amount of O2 required for their
survival.
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Soluble, Insoluble
Ionic compounds that
• dissolve in water are soluble salts
• do not dissolve in water are insoluble salts
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Solubility Rules
Soluble salts typically contain at least one ion
from Groups 1A (1), NO3−, or C2H3O2− (acetate).
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Using Solubility Rules
A barium sulfate-enhanced
X-ray of the abdomen
shows the large intestine.
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Learning Check
Predict if the following compounds are soluble
in water.
A. Li3PO4
B. PbSO4
C. Ca(NO3)2
D. AgCl
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Solution
Predict if the following compounds are soluble
in water.
A. Li3PO4
Soluble in water (Li+)
B. PbSO4
Not soluble in water
C. Ca(NO3)2
Soluble in water (NO3−)
D. AgCl
Not soluble in water
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Guide to Writing Equations for
Insoluble Salt
A chemical equation shows the complete formulas
of all the compounds in a reaction.
Pb(NO3)2(aq) + 2NaCl(aq)
PbCl2(s) + 2NaNO3(aq)
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Guide to Writing Equations for
Insoluble Salt
An ionic equation shows all the ionic
compounds as separate ions.
Pb2+(aq) + 2NO3−(aq) + 2Na+(aq) + 2Cl−(aq)
PbCl2(s) + 2Na+(aq) + 2NO3−(aq)
A net ionic equation shows only the ions that
react to form a solid.
Pb2+(aq) + 2Cl−(aq)
PbCl2(s)
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Guide to Writing Equations for
Insoluble Salt
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Learning Check
When solutions of AgNO3 and NaCl are mixed, a
white solid forms. Write the ionic and net ionic
equations for the reaction.
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Solution
When solutions of AgNO3 and NaCl are mixed, a
white solid forms. Write the ionic and net ionic
equations for the reaction.
Step 1 Write the ions of the reactants.
Ag+(aq) + NO3−(aq) + Na+(aq) + Cl−(aq)
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Solution
When solutions of AgNO3 and NaCl are mixed, a
white solid forms. Write the ionic and net ionic
equations for the reaction.
Step 2 Write the combinations of ions and
determine if any are insoluble.
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Solution
When solutions of AgNO3 and NaCl are mixed, a
white solid forms. Write the ionic and net ionic
equations for the reaction.
Step 3 Write the ionic equation including
any solid.
Ag+(aq) + NO3−(aq) + Na+(aq) + Cl−(aq)
AgCl(s) + Na+(aq) + NO3−(aq)
Ionic equation
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Solution
When solutions of AgNO3 and NaCl are mixed, a
white solid forms. Write the ionic and net ionic
equations for the reaction.
Step 4 Write the net ionic equation.
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Solution
Ag+(aq) + Cl−(aq)
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AgCl(s)
Net ionic equation