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Solutions
Concentration and Solubility
Mix and Flow 2.2
What are the Chemical solutions you see:
Solutions
• Homogeneous mixture of two or
more substances
▫ The dissolved substance is completely
dispersed throughout the solution
 Concentration is the SAME throughout
▫ Usually a solid is dissolved in a liquid
 Some liquids can dissolve in one
another
 Some gases can be dissolved in liquids
“Anatomy” of a Solution
Properties of Solutions
• Small particles
• Evenly distributed particles – will not
separate
• Solvent: the substance DOING the
dissolving
• Solute: the substance BEING
dissolved
Which is the SOLUTE?
Solute and Solvent
• Typically the substance in greater proportion is
the SOLVENT
• The substance in minor proportion is the
SOLUTE
Measuring Concentration
• Concentrated and diluted are NOT exact terms.
• Concentration of a solution describes the amount of
solute dissolved in a specific amount of solvent
(typically amount of solute for 100mL).
• Example:
▫ a solution with 50 g of solute dissolved in 100mL of
water has a concentration of 50g/100mL
There are other ways to measure concentration, such
as percentage, g/mL, etc.
We will focus on g/100mL
Let’s Practice
• A 355 mL can of Iced Tea
has 20g of sugar. What is
the concentration (in
g/100mL) of the iced
tea?
• Mr. Chappell’s morning
coffee is in a big, 473mL
cup and contains 0.252g
of caffeine. What is the
concentration of caffeine
of Mr. Chappell’s coffee?
Solubility
• Amount of substance that dissolves in a
given amount of solvent (at a given
Temp)
• Commonly:
▫ Grams solute/100 g solvent
▫ Grams solute/100 mL water
Solubility
dissolve - ability
Saturated Solutions
• A solution has reached it’s saturation point when
no more solute is able to dissolve in a fixed
volume of solvent at a given temperature
• Considered saturated when the concentration
of the solution is equal to its solubility of solute
• Considered unsaturated when the
concentration of the solution is less than its
solubility of solute
• Considered super-saturated when the
concentration of the solution is greater than its
solubility of solute
Factors Affecting Solubility
Mix and Flow 2.3
Solubility
• Maximum amount of substance
that dissolves in a given amount
of solvent (at a given Temp)
• Commonly:
Solubility
dissolve - ability
Solubility
• Solubility is largely dependent on (at least) three
factors:
▫ Type of Solute
▫ Type of Solvent
▫ Temperature of the Solution
Types of Solutes and Solvents
• The most common solvent is Water – the
universal solvent
• The term aqueous or (aq) describes a solution in
which the solvent is water
• Not all solutes and solvents are liquid!
▫ Brass (zinc and nickel)
▫ Seawater (salt and other substances in water)
▫ Air (Many different gasses in Nitrogen)
Types of Solutes and Solvents
The type of solute and solvent affects solubility
due to interactions between the solvent and
solute!
These interactions affect the amount of solute
suspended in solution.
Solubility Changes With Temperature
• For most common solids, or liquids, you can
dissolve more solute as the temperature of the
solvent increases.
• The OPPOSITE is true for gases! As the
temperature increases, the solubility of a
gaseous solute decreases in a liquid or gas
solvent.
Solids and Liquids
Gases
What is thermal pollution?
What impacts could thermal pollution have on an aquatic environment?
Solubility Factors
• Greater contact between solvent and solute
molecules means faster dissolving
▫ Crushing, stirring increase surface area – so
increase rate of solution
Solubility Factors
• Temperature
▫ Solids & Liquids
 Solubility increases with Temperature
▫ Gases
 Solubility decreases with Temperature
 (Gas escapes to the atmosphere with increased
energy)
 Carbonated beverages go flat
• Pressure
▫ Solids & Liquids
 Very little effect – doesn’t increase solubility
▫ Gases
 Solubility increases with Pressure – squeezes gas
molecules into the solvent