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A solution is composed of:Solute: the substance being dissolved
Usually a solid. Can be a gas or another liquid.
Solvent: the substance doing the dissolvingUsually water (aq)
Soluble: when a solid is able to dissolve in a liquid
Insoluble: when a solid cannot dissolve (precipitate)
Immiscible: two liquids that will not mix
Miscible: two liquids that will mix
Solvation process:What is happening at the molecular level when a
solid dissolves in a liquid?
The solid must be “picked apart” layer by layer by the liquid.
Water makes a great solvent because it is polar.
1. TemperatureHot: water molecules move rapidly and contact
solid often.
Cold: water molecules move slowly. Little contact.
2. Concentration of solute or solvent
More solvent: increases rate of liquid coming into contact with solid.
More solute: Less water to suspend solid.
4. Surface area of substance
The larger the surface area (larger crystal), the more layers there are to pick apart.
Smaller crystals also have more surface area in proportion to their volume.
6. Type of substancesSome solutes are
more easily dissolved due to less “intermolecular” attraction.
Some liquids are better solvents (polarity).
Essential question: What factor has the greatest effect on the
rate of solution formation?
Choose any two factors.
You must test an increase and a decrease for each factor.
You must have a control.
You should keep all other conditions constant.
1. Percent Concentration:
Used more in “every day” life.
What are some examples of solutions in your world?
% Concentration = Mass or volume of solute X
100
Mass or volume of solute + solvent
Remember: solution = solute + solvent
Examples for % concentration:
1. What is the concentration of a solution that has 25 grams of salt dissolved in 250 ml of water?
2. Ocean water has a salt concentration of 3.5% How much salt and water would I need to make 500 ml of ocean water?
3. Power equipment uses a 2% oil/gas mixture. How much oil (solute) and gas (solvent) would I need to make 2 liters?
2. Molarity and Molar concentrations
How chemists make solutions.
A 1 molar solution is a solution in which 1 mole of a compound is dissolved in a total volume of 1 litre.
1 M = molar mass of solute dissolved in
total volume of 1000 ml
How to make a molar solution:1. Determine chemical
formula of solute.
2. Calculate molar mass of solute.
3. Dissolve solute in water to a final volume of 1000 ml.
Molarity examples:1. How do you make a one molar solution of calcium
chloride?
2. How do you make 500 ml of a one molar solution of calcium chloride?
3. How do you make a 2 molar solution of sodium chloride?
4. What is the molarity of a sodium chloride solution that has 30 grams dissolved in 1000 ml?
Solubility:How much of a solid will dissolve in
a given amount of liquid at a given temperature.
Often look at solubility curves, or saturation curves.
To
Sol.
To
Sol.
Solids dissolved in liquids Gases dissolved in liquids
As Temperature increases, Solid solubility increases.
As Temperature increases, Gas solubility decreases.
What type of solutions exist?
SATURATED SOLUTION
no more solute can be
dissolved
UNSATURATED SOLUTION
more solute can be dissolved
SUPERSATURATED SOLUTION
Contains more solute than it
normally would at that temperature.
increasing concentration
A supersaturated solution is unstable, and crystallization will occur upon cooling.
A “seed” crystal will disturb the equilibrium and start the crystallization process.
Let’s watch…
http://www.stevespanglerscience.com/experiment/00000078
Solubility of Sodium Acetate
Temperature (oC)
025 50 75 100
Solu
bili
ty(g
/100 g
H2O
)
50
100
150Supersaturated
solution
Unsaturated solution
Saturated
Charles H.Corwin, Introductory Chemistry 2005, page 378
In the world of solubility, “Like dissolves Like”
Polar solvents will dissolve polar molecules.
Non-polar solvents will dissolve non-polar molecules.
Example: Oil-based paint is non-polar, and requires non-
polar paint remover for cleaning.Water-based paint can be cleaned with water.
Vitamins
Multi Vitamin Provides many essential
vitamins “Expensive urine”
Water Soluble Vitamin C Must be replenished
regularly
Fat Soluble Can overdose Vitamin A Can be ingested periodically,
stored in body fat