Solutions
and Their
Properties
Aim
Solution1a
– what is a
solution?
Solutions Review
• Heterogeneous mixture
– An unevenly distributed
(clumpy) mixture
• Solution
– A homogeneous mixture
– Mixtures that are evenly distributed
• Parts of a solution
– Solute - the dissolved substance in a solution
– Solvent - the substance doing the dissolving in a
solution
Examples - Solutions
• Gas in gas
– air (various gases)
• Gas in liquid
– cola (water and CO2)
– Effervescence – the bubbles you
see are escaping gas molecules
• Liquid in liquid
– beer (alcohol and water)
• Solid in liquid
– saltwater, sugar water
• Liquid in solid
– mercury in gold amalgam for fillings
• Solid in solid
– alloys like steel and brass
Solubility
• Dissolution (dissolving)
– the separation of solute particles by
solvent particles
– Ex: salt (ionic) and water (polar)
– The attractive forces between solute
and solvent particles are slightly broken
– The different particles attract each other
with forces of similar strength
• Dissolving is based on polarities
– “Like dissolve like”
– polar solvents dissolve polar solutes
– Nonpolar solvents dissolve non polar
solutes
Solution Types
• Saturated solution
– The amount of solute needed to just saturate a given
amount of solvent
– These are the points ON the solubility curve
• Unsaturated solution
– When more solute can
still be dissolved in
solution
– The area below the
solubility curve
• Supersaturated solution
– When more solute than
normal is dissolved in solution
– The area above the solubility curve
Table G Solubility
Curves
•
Curves represent
the solubility
– in grams,
– of various
substances (solids
and gases),
– in 100 g (100 mL)
of water,
– at varying
temperatures
Solubility Curves
• Relationships:
– Solids in the chart
– (KNO3, KI, NaCl, etc)
– As the temperature
increases, the solubility of
solids in solution increases
(more can dissolve)
– Gases in the chart
– (SO2, NH3, and HCl)
– As the temperature increases,
the solubility of solids in
solution decreases (less can
dissolve)
Reading Table G - Solubility Curves
1. What is the solubility of KI (potassium iodide) at
20oC?
145 g
2. What is the difference in solubility for ammonia
when the temperature changes from 10oC to
90oC?
60 g difference
3. Which substance at 10oC has the lowest solubility
in 100 g of water? KClO3
4. At what temp does KNO3 and NaNO3 have the
same solubility? 71oC
5. What is the solubility of KCl at 55oC in 200 g of
water? 44 gram of KCl / 100 gram of water so
200 grams of water = 88 grams of KCl
Soluble vs Insoluble substances
Aim Solutions2b
- How do I keep
my cola fizzy?
Factors Affecting Solubility
• Various factors will increase (or decrease) the
solubility of substances in a liquid solution
• Surface Area
• For solids
– the amount of the solute’s surface that is exposed to
solvent
– By reducing the particle size (for example, by crushing)
– dissolving rate increases
– Example: sugar cube vs granulated sugar dissolving rates
• For gases
– There is no reducing the particle size for a gas
– Therefore, surface does not affect gas solubility
Factors Affecting Solubility
• Stirring
– For solids
• Increases solubility of the solid in solution
• Increases kinetic energy
• Exposes fresh solvent to solute
– For gases
• Decreases solubility
of the gases in solution
• Increases kinetic energy
• Gases more easily
escape solution
Factors Affecting Solubility
• Pressure
– For solids
• Does not affect the
solubility
• You can’t “squeeze” a
solid or a liquid
– For gases
• Increases the solubility of
the gases in solution
• Squeezes a gas into the
liquid
• Gases go into solution or
are held in solution more
Factors Affecting Solubility
• Temperature
– For solids
•As the temperature
increases
•The solubility
increases
– For gases
•As the temperature
increases
•The solubility
decreases
Application of what you just learned…
• What factors will keep your cola fizzy?
–
–
–
–
•
Lower the temperature
Don’t stir or shake it
Increase gas pressure
Surface area – nothing you can do!
What factors will dissolve your sugar into
your coffee faster?
– Raise the temperature
– Stir or shake it
– Crush the solid solute so there is more
surface area
– In terms of pressure – nothing you can do!
Chemical Effects on Solubility
•
Different substances have different
solubilities
– Their chemical nature does not always allow
them to exist in solution
– For example
– AgNO3 – highly soluble in water
– AgCl – insoluble in water (or nearly so)
•
See Table F for Solubility Guidelines for
Aqueous Solutions
See Table F for Solubility Guidelines for
Aqueous Solutions
•
•
Left side of chart
Soluble substances
with exceptions
•
•
Right side of chart
Insoluble substances
with exceptions
Reading Table F
Compound
Soluble or
insoluble?
Reason
KI
Soluble
All Group 1 elements soluble
AgNO3
Soluble
All nitrates soluble
Fe(OH)3
Insoluble
Hydroxides insoluble
NH4Cl
Soluble
Ammonium always soluble
BaSO4
Insoluble
Barium is SO4 exception
Na2SO4
Soluble
All Group 1 elements soluble
PbCrO4
Insoluble
Chromates are insoluble
Concentration
Strength
Aim Solutions 3c
– how strong is
my ice tea?
Nerd (def): (noun)
an individual
persecuted for their
superior skills or
intellect, most often
by people who fear
and envy them…
Solution Strength or Concentration
•
Concentration
– The strength of a solution
– A measure of the quantity of solute in a given
solvent
– Concentrated
• high levels of
solute per solvent
– Dilute – low levels
of solute per
solvent
• Molarity
– A measure of concentration in moles per liter (M)
– Molarity is the number of moles of solute dissolved in
1 liter of solution
– Concentration formula: molarity = moles of solute
liters of solution
• Mr. Foley pours 2.80 moles of salt into 2.00 liters of
solution. What is the concentration of the salt solution?
M = moles
liter
x M = 2.80 moles
2.00 L
x M = 2.80 moles = 1.40 M solution of salt
2.00 L
Calculating the molarity of solutions
•
A student dissolves 2.00 moles of NaCl in 8.00 L of
solution. What is the molarity or concentration of the
solution?
M = moles
liter
2.00 M NaCl = x moles
8.00 L
x = 16.0 moles of NaCl
•
Mr. Foley adds 2.80 moles of salt to another container,
making a 5.20 molar solution. How much solution did he
make?
M = moles
liter
5.20 M = 2.80 moles
xL
x L = 2.80 moles = 0.538 L of solution
5.20 M
•
Parts per million
– Measures very dilute solution
– Some substances are toxic / carcinogenic in very
small amounts
– Formula on Table T
ppm = mass in grams of solute x 106
mass of solution
– Examples
• Carbon monoxide
– 100 ppm can cause health issues
– 1 balloon in a gym’s worth of air!
• Arsenic
– 0.05 ppm is dangerous
– 1 drop in a gallon container!
Calculating parts per million in very dilute
solutions
Examples
A given toxin has a concentration of 2.20 grams
per 10,000 grams of solution. If only 200.0 ppm is
required to kill you, will you get sick if you drink
the water?
ppm of solute = mass of solute x 106
mass of solution
ppm of solute = 2.20 g of poison
x 106
10,000 g of solution
ppm of solute = 220 ppm
you are over the limit of toxin allowed!
Solution Concentration - ppm
Ex: Dr. Phaux Lee, a mad scientist hidden within the
bowels of Hauppauge HS, has added 200.0
grams of his truth serum to a teacher’s room
Poland spring water container with 20,000 grams
of water. What is the concentration in parts per
million?
ppm =
mass of solute x 106
mass of solution
ppm = 200.0 grams of serum
x 106
20,000 g of water + 200 g of serum
ppm = 200.0 grams of serum x 1,000,000
20,200 g of solution
ppm = 990 ppm – that’s a lot of truth serum!
Other Effects of Solute in solution
Colligative properties
• Boiling and freezing points are affected by solutes
dissolved in a solution
• Dependent on the number of particles or ions in
the solution
• Examples: how many different particles dissolve
in:
• Glucose (C6H12O6)?
– 1 only – glucose doesn’t break up
• Sodium chloride (NaCl)?
– 2 particles – a Na+ ion and a Cl- ion
• Rock salt (CaCl2)
– 3 particles – 1x Ca+2 ion and 2x Cl- ions
Solute Effects on Boiling Point
• Solute particles in solution bond with solvent
particles
• This lowers the vapor pressure of the solvent
• Therefore RAISING the boiling point
• Example:
– table salt (NaCl) in water for cooking pasta
– 2.00 moles of NaCl (117 g) are added to 1.00 kg
of water. What is the new boiling point?
– NaCl divides into Na+ ions and Cl- ions, for a total
of 4 moles of solute
– Boiling point = 100oC + (4 x 0.52oC) = 102.04oC
Solute Effects on Freezing Point
• Solute particles in solution bond with solvent
particles and inhibit crystal formation as the
temperature drops
• This lowers the freezing point of the solvent
• Therefore lowering the freezing point
• Example:
– Rock salt (CaCl2) placed on your driveway
– 2.00 moles of CaCl2 (111 g) are added to 1.00 kg
of water. What is the new freezing point?
– CaCl2 divides into Ca+2 ions and Cl- ions, for a
total of 6 moles of solute
– Freezing point = 0oC - (6 x 1.86oC)
= -11.2oC or 11.84oF
– this is the temp the air must get to in order to
freeze the water