Properties of Solutions

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Properties of Solutions
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Solute
A solute is the dissolved substance in a solution.
Salt in salt water
Sugar in soda drinks
Carbon dioxide in soda drinks
Solvent
A solvent is the dissolving medium in a solution.
Water in salt water
Water in soda
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Calculations of Solution Concentration
Mass percent - the ratio of mass units of solute
to mass units of solution, expressed as a percent
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Calculations of Solution Concentration
Molarity - the ratio of moles of solute to liters
of solution
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Like Dissolves Like
Nonpolar solutes dissolve best in nonpolar
solvents
Fats Benzene
Steroids Hexane
Waxes Toluene
Polar and ionic solutes dissolve best in polar
solvents
Inorganic Salts Water
Sugars Small alcohols
Acetic acid
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Solubility Trends

• The solubility of MOST solids increases with
  temperature.
• The rate at which solids dissolve increases with
  increasing surface area of the solid.
• The solubility of gases decreases with increases
  in temperature.
• The solubility of gases increases with the
  pressure above the solution.

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Therefore
Solids tend to dissolve best when

• Heated
• Stirred
• Ground into small particles

Gases tend to dissolve best when

• The solution is cold
• Pressure is high

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Saturation of Solutions

• A solution that contains the maximum amount of
  solute that may be dissolved under existing
  conditions is saturated.
• A solution that contains less solute than a
  saturated solution under existing conditions is
  unsaturated.
• A solution that contains more dissolved solute
  than a saturated solution under the same
  conditions is supersaturated.

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Solubility Chart
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Henrys Law
The concentration of a dissolved gas in a
solution is directly proportional to the pressure
of the gas above the solution
S1/P1 S2/P2 S solubility in
g/L P pressure
Applies most accurately for dilute solutions of
gases that do not dissociate or react with the
solvent
Yes ? CO2, N2, O2
No ? HCl, HI
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Definition of Electrolytes and Nonelectrolytes
An electrolyte is

• A substance whose aqueous solution conducts
• an electric current.

A nonelectrolyte is

• A substance whose aqueous solution does not
• conduct an electric current.

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Electrolytes?

1. Pure water
2. Tap water
3. Sugar solution
4. Sodium chloride solution
5. Hydrochloric acid solution
6. Lactic acid solution
7. Ethyl alcohol solution
8. Pure sodium chloride

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Answers to Electrolytes
NONELECTROLYTES
ELECTROLYTES

• Pure water
• Sugar solution
• Ethanol solution
• Pure NaCl

• Tap water (weak)
• NaCl solution
• HCl solution
• Lactate solution (weak)

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Suspensions and Colloids
Suspensions and colloids are NOT solutions.
Suspensions The particles are so large that they
settle out of the solvent if not constantly
stirred.
Colloids The particles intermediate in size
between those of a suspension and those of a
solution.
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Types of Colloids
Examples Dispersing Medium Dispersed Substance Colloid Type
Fog, aerosol sprays Gas Liquid Aerosol
Smoke, airborn germs Gas Solid Aerosol
Whipped cream, soap suds Liquid Gas Foam
Milk, mayonnaise Liquid Liquid Emulsion
Paint, clays, gelatin Liquid Solid Sol
Marshmallow, Styrofoam Solid Gas Solid Foam
Butter, cheese Solid Liquid Solid Emulsion
Ruby glass Solid Solid Solid sol
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The Tyndall Effect
Colloids scatter light, making a beam visible.
Solutions do not scatter light.
Which glass contains a colloid?
colloid
solution