HC Unit 10: Solutions
Name: _______________________
Solution Definitions
solution: a homogeneous mixture
--- e.g.,
alloy: a solid solution of metals
-- e.g.,
solvent: the substance that dissolves the solute
soluble: “will dissolve in”
miscible: refers to two liquids that mix evenly in all proportions
-- e.g.,
Factors Affecting the Rate of Dissolution
1. temperature
As temp. / , rate…
2. particle size
As particle size / , rate…
3. mixing
Rate increases with…
4. nature of solvent or solute
Classes of Solutions
aqueous solution:
amalgam:
e.g.,
tincture:
e.g.,
organic solution:
e.g.,
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/
/
Non-Solution Definitions
insoluble: “will NOT dissolve in”
e.g.,
immiscible: refers to two liquids that will NOT form a solution
e.g.,
suspension: appears uniform while being stirred, but settles over time
e.g.,
Molecular Polarity
nonpolar molecules:
-- ____ are shared equally
-- tend to be symmetric
e.g.,
polar molecules:
-- ____ are NOT shared equally
e.g.,
“Like dissolves like.”
Using Solubility Principles
Chemicals used by body obey solubility principles.
-- water-soluble vitamins:
e.g.,
-- fat-soluble vitamins:
e.g.,
Dry cleaning employs nonpolar liquids.
-- polar liquids damage some fabrics, e.g.,
-- also, dry clean for stubborn stains, e.g.,
-- tetrachloroethylene was in longtime use
2
emulsifying agents (emulsifiers):
-- molecules w/both a polar AND a nonpolar end
-- allows…
e.g., soap
eggs
lecithin
detergent
MODEL OF A SOAP MOLECULE
soap
vs.
detergent
-- made from…
-- made from…
--
Hard water contains minerals w/ions like Ca2+, Mg2+, and Fe3+ that
replace Na+ at polar end of soap molecule. Soap combines
w/these
to form an insoluble precipitate:
micelle: a liquid droplet covered w/soap or detergent molecules
Solubility
SOLUBILITY
CURVE
unsaturated: sol’n could hold more
KNO3 (s)
solute;
saturated: sol’n has “just right” amt.
KCl (s)
Solubility
(g/100 g
H2O)
of solute;
supersaturated: sol’n has “too much” solute
HCl (g)
dissolved in it;
Temp.
(oC)
Solids dissolved in liquids
Gases dissolved in liquids
Sol.
Sol.
To
To
As To , solubility ___
As To , solubility ___
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Solubilities of Selected Solutes in Water
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EX.
Using a solubility curve, classify as unsaturated, saturated, or supersaturated.
80 g NaNO3 @ 30oC
per
100 g
H2O
45 g KCl @ 60oC
30 g KClO3 @ 30oC
70 g Pb(NO3)2 @ 60oC
Per 500 g H2O, 100 g KNO3 @ 40oC
EX.
Describe each situation below.
(A) Per 100 g H2O, 100 g NaNO3 @ 50oC.
(B) Cool sol’n (A) very slowly to 10oC.
(C) “Stress” sol’n (B) by jostling the beaker or adding a seed crystal.
Glassware – Precision and Cost
beaker
1000 mL + 5%
vs.
volumetric flask
1000 mL + 0.30 mL
When filled to 1000 mL line,
how much liquid is present?
water in
grad. cyl.
mercury in
grad. cyl.
**
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Ions in Aqueous Solution
Pb(NO3)2(s)
Pb(NO3)2(aq)
NO3–
Pb2+
NO3–
add
NO3–
Pb2+
water
NO3–
NaI(s)
Na+
NaI(aq)
add
I–
Na+
water
I–
Mix them
and get the
overall ionic equation…
Cancel spectator ions to get net ionic equation…
Mix together Zn(NO3)2(aq) and Ba(OH)2(aq):
Zn(NO3)2(aq)
Ba(OH)2(aq)
NO3–
OH–
Zn2+
Ba2+
NO3–
OH–
Mix them
and get the
overall ionic equation…
Cancel spectator ions to get net ionic equation…
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Concentration…a measure of solute-to-solvent ratio
concentrated
dilute
How much solute?
How much solvent?
Dilute a conc. soln. by…
Concentrate a diluted soln. by…
Molarity
EX.
molarity (M) = moles of solute
L of sol’n
How many mol of sodium hydroxide are req’d to make 1.35 L of 2.50 M sol’n?
What mass of sodium hydroxide is this?
EX.
What mass of Mg3(PO4)2 is needed to make 925 mL of a 0.45 M soln?
EX.
What is the concentration when 58.6 g of barium hydroxide are in 5.65 L of sol’n?
EX.
You have 10.8 g potassium nitrate. How many mL of sol’n will make this a 0.14 M
sol’n?
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mass
Molarity and Stoichiometry
mass
vol.
vol.
part.
EX.
Pb(NO3)2(aq) +
KI (aq) 
PbI2(s) +
part.
KNO3(aq)
What volume of 4.0 M KI sol’n is req’d to yield 89 g PbI2?
Strategy:
(1)
(2)
EX.
How many mL of a 0.500 M CuSO4 sol’n will react w/excess Al to produce 11.0 g Cu?
Dilutions of Solutions
Acids (and sometimes bases) are purchased in concentrated
form (“concentrate”) and are easily diluted to any desired
concentration.
**Safety Tip:
Dilution Equation:
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EX.
Conc. H3PO4 is 14.8 M. What volume of concentrate is req’d to make 25.00 L of
0.500 M H3PO4?
How would you mix the above sol’n?
1. Measure out ________ L of conc. H3PO4.
2. In separate container, obtain ~20 L of cold H2O.
3. In fume hood, slowly pour conc. into cold H2O.
4. Add enough H2O until 25.00 L of sol’n is obtained.
EX.
You have 75 mL of conc. HF (28.9 M); you need 15.0 L of 0.100 M HF. Do you have
enough to do the experiment?
Dissociation occurs when neutral combinations of particles
separate into ions while in aqueous solution.
sodium chloride
NaCl 
hydrochloric acid
HCl 
nitric acid
HNO3 
chloric acid
HClO3 
sodium hydroxide
NaOH 
barium hydroxide
Ba(OH)2 
In general, ________ yield hydrogen (H+) ions
in aqueous solution; ________ yield hydroxide (OH–) ions.
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Strong electrolytes exhibit nearly 100% dissociation.
Na+
NaCl
Cl–
+
Say we put 1000
NaCls into water…
Weak electrolytes exhibit little dissociation.
CH3COOH
CH3COO–
+
H+
Now put 1000
CH3COOHs into water…
electrolytes: solutes that dissociate in sol’n
-- conduct elec. current because of free-moving ions
-- e.g.,
-- are crucial for many cellular processes
-- obtained in a healthy diet
--
nonelectrolytes: solutes that DO NOT dissociate
--- e.g.,
Colligative Properties 
Compared to a pure solvent’s…
a sol’n w/that solvent has a…
…normal freezing point (NFP)
…normal boiling point (NBP)
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For example…
NBP
water SOLUTION
WATER
(i.e., with some solute
– like salt or sugar –
mixed in)
NFP
Applications of Colligative Properties
EX.
(NOTE: Data are fictitious.)
salting roads in winter
FP
BP
FP
BP
water
water + a little salt
water + more salt
EX.
antifreeze (AF) (a.k.a., “coolant”)
water
water + a little AF
50% water + 50% AF
EX.
law enforcement
white powder
starts
melting at…
finishes
melting at…
A
B
C
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penalty, if
convicted
Calculations with Colligative Properties
Adding a nonvolatile solute to a solvent decreases the solution’s freezing point (FP)
and increases its boiling point (BP).
The freezing point depression and boiling point elevation are given by:
Tx = FP depression or BP elevation
Kx = Kf (molal FP depression constant) or Kb (molal BP elevation constant)
-- they depend on the solvent
-- for water:
m = molality of solute
i = van’t Hoff factor (accounts for # of particles in solution)
In aq. soln., assume that…
-- i = __ for nonelectrolytes
-- i = __ for KBr, NaCl, etc.
an integer. Use the guidelines unless
given information to the contrary.
-- i = __ for CaCl2, etc.
EX.
In reality, the van’t Hoff factor isn’t always
Find the freezing point and boiling point of a solution containing 360 g barium
chloride and 2.50 kg of water.
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