The Solution Process
Chapter 13 part 3: Solubility
Read: BLB 13.1 - 13.3
HW: BLB 13:7,15, 21, 23, 33;
Packet 13:6-12
Know: Factors that affect solubility
NaCl dissolves in water. What kind of IMF?
! thermodynamics of solution process
! intermolecular interactions (like
dissolves like)
! temperature effects
! pressure effects
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Chapter 13 Part 3
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Chapter 13 Part 3
Dissolution requires 3 Steps:
1. break solute-solute
interactions
! EXO OR ENDOTHERMIC?
2. break solventsolvent interactions
! EXO OR ENDOTHERMIC?
Enthalpy changes
accompanying the solution
process
L: Net exothermic process ("Hsoln<0)
Example: CuSO4
3. form solute-solvent
interactions
! EXO OR ENDOTHERMIC?
Is Dissolution overall Exo or
endothermic?
Is Dissolution Spontaneous?
Processes occur spontaneously when:
• energy is released (exothermic)
• disorder increases (increase in entropy)
! An endothermic process can be
spontaneous if the increase in
entropy (disorder) is large enough.
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Chapter 13 Part 3
R: Net endothermic process ("Hsoln>0)
Example: NH4NO3
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Chapter 13 Part 3
Is the dissolution of CH3COONa (sodium acetate)
exothermic or endothermic?
The Solution Process is a
DYNAMIC EQUILIBRIUM
1. exothermic
2. endothermic
solvent
solute
Solute
dissolve
+
!!!!"
Solvent !"""""
solution
crystallize
Define Saturated solution:
Define Supersaturated solution:
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Chapter 13 Part 3
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Chapter 13 Part 3
Dependence of Solubility on
Temperature
SOLUBILITY IS:
Effect of
Temperature
on solubility of
ionic solids
FACTORS THAT AFFECT SOLUBILITY
1. Temperature
! Effect of temperature on solubility of
ionic solids
! Effect of temperature on solubility of
gases
2. IMF’s: Type and Strength
Effect of
temperature
on solubility
of gases
3. Pressure
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Chapter 13 Part 3
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Chapter 13 Part 3
Effect of Intermolecular Forces
on Solubility
In general: like dissolves like
Like dissolves like
What kind of molecule is CH3CH2OH?
What kind of IMF’s?
Is it an electrolyte?
. Polar solvents dissolve what kind of
solutes?
. Nonpolar solvents dissolve what kind of
solutes?
If the intermolecular forces broken
and formed are approximately equal,
dissolution is probable.
Molecule
Which one of the following will be most
soluble in benzene (C6H6(l))?
1.
2.
3.
4.
5.
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H2O(l)
CH3OH(l)
HCl(l)
CH3CH2OH(l)
heptane
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solubility in water
at 25°C (g/100g of H2O)
CH3OH
CH3CH2OH
CH3CH2CH2OH
CH3CH2CH2CH2OH
CH3CH2CH2CH2CH2OH
CH3CH2CH2CH2CH2CH2OH
total
total
total
8.06
2.82
0.62
As the length of hydrocarbon chain increases,
what happens to the solubility in water?
Chapter 13 Part 3
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Chapter 13 Part 3
Ammonia Fountain
Effect of Pressure on Solubility
Does pressure affect solid, liquid or gas
solubility?
What happens to solubility of a gas when:
Increase Pg?
NH3 gas
H2O
Decrease Pg?
HENRY’S Law
Relationship between:
solubility
and pressure
Cg (note: text uses Sg)
H2O +
phenolphthalein
Pg
(pink/basic solution)
amount of gas dissolved (Cg)
is proportional to the partial pressure of
that gas (Pg) above the solution.
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Chapter 13 Part 3
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To increase the solubility of N2 in water
1.
2.
3.
4.
Which of the following aqueous solutions has the
greatest total concentration of ions?
1. 0.2M NH4NO3
increase T
decrease T
increase P
decrease P
2. 0.2M Pb(NO3)2
3. 0.2M Na2SO4
4. 0.2M AlPO4
How will the solubility of KClO3 be
effected by an increase in pressure?
5. 0.2M AlBr3
6. 0.5M CH3COOH (acetic acid)
1.
2.
3.
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increase solubility
decrease solubility
no effect on solubility
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Chapter 13 Part 3
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Chapter 13 Part 3