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Solutions
CPS Chemistry
Definitions
Solutions A homogeneous mixture of two or more
substances in a single phase Soluble
Capable of being dissolved
Solvent Dissolving medium in a solution
What is doing the dissolving
Solute Substance dissolved in a solution
What is dissolved
Example Sugar in tea –
tea is solvent, sugar solute
Types of Solutions
May exist as gasses, liquids or solids One component is designated as
solvent and one as solute Chart on pg. 396
Phase If there are two different types of
substances it is a phase change Water + salt; water and gas
Same phase Water and apple juice
This is an aqueous solution Means there is water involved
Alcohol and liquid Tincture solution Means there is alcohol involved
Mixtures
2 or more substances when each retains its properties
Homogeneous Uniform distribution of particles 0.01-1nm size particles, can be atoms Can be physically separated Ex. Salt water, air Also called solution
Heterogeneous Distribution of particles is not uniform
Can be separated by physical means
Particle size 1-1000 nm (nanometer)
Suspensions
When particles in a solvent are so large that they settle out unless stirred constantly
Gravity pulls particles to bottom of container
Particles >1000nm in diameter, 1000 times as large as atoms
Ex. Italian salad dressing, muddy water
Can be separated by passing liquid through a filter
Colloids
Has particles that are intermediate in size and they remain dispersed in the solute
1-1000nm particle size Emulsion or foam are specific types Mayonnaise is an emulsion of egg and
oil
The Tyndall effect
Is a sign that it may be a colloid The particles are not large enough to
be seen, but large enough to scatter light
Ex: headlights on a foggy night
Test tube
Light Beam
Test tube
Light Beam
Tyndall Effect, beam of light can be seen in suspensions and colloids
No Tyndall Effect, beam of light cannot be seen in solutions
Electrolytes vs. Nonelectrolytes
Electrolyte A substance that dissolves in water to
give a solution the ability to conduct electricity
Nonelectrolyte A substance that when dissolved in water
to make a solution that does not conduct electricity
When ionic compounds dissolve, the positive and negative ions separate from each other and are surrounded by water molecules
When the ions are free to move, electricity moves easily
How to Make Solutions
You need to know the: Solubility –the maximum amount solute
can dissolve in a solvent Rate – how fast the solute dissolves
Factors that affect rate of dissolution
Surface area of the solute The larger the surface area, the more
quickly it dissolves Agitation of a solution
When you stir or shake the solute particles are dispersed throughout the solvent, and it increase the rate of dissolution
Saturated Solutions A solution that contains the maximum
amount of dissolved solute is saturated
The factors that determine saturation are mass of solvent, mass of solute and the temperature
When a solution contains less than the maximum saturation it is considered unsaturated
Supersaturate
A solution that contains more dissolved solute than a saturated solution contains under the same conditions
But will form crystals when disturbed or cooled
Like dissolves like
The rule for predicting whether one substance will dissolve in another is related to the type of bonding, the polarity of a molecule and the intermolecular forces between the solute and solvent
Things need to be similar for them to dissolve
Solvent Solute = Solution
Polar Polar = yesPolar non-polar= noNonpolar Polar = noNonpolar Nonpolar = yes
Reminder molecule polarity
More Vocab.
Immiscible Liquid solutes and solvents that are not
soluble in each other Oil and water Oil and salt
Miscible Liquids that dissolve freely in one
another in any proportion Water and food coloring
Back to Temperature- Solubility Increase temp =increase KE=
increase in solubility + increase in rate Higher temps dissolve faster( Liquids)
BUT Gasses act differently
Increase temp = decrease solubility Because gasses will leave solution at high
temps
Pressure –solubility
There is no difference to solids or liquids, but with an increase in pressure it will increase the solubility of a gas For example CO2 dissolved in a solution
of sucrose and water (soda) will come out of solution when the pressure is decreased (opening the bottle, lets the soda bubble)
Size of the Particle – rate
Because the dissolution occurs only at the surface of the solute, when you crush a substance,
You get a larger surface, so you increase the rate at which it is dissolved
Stirring - rate
When you agitate the solvent, you increase the contact with the surface of the solute
You increase the rate
Amount of Solute -rate
As you increase the amount of solute you want to dissolve
You decrease the solubility and rate
Concentration
A measure of the amount of solute in a given amount of solvent or soulution
MATH IS INVOLVED
Molarity The number of moles of solute in one
liter of solution Molar mass- as a reminder it is the
mass listed on the PTE.. If it is for a compound, you simly add the masses of the atoms of the emperical formula
Ex. H2O H=1.00 O=15.99 total molar mass is 1.00+1.00+15.99 =17.99g
Formula
Amount of solute (mol)
Molarity ( M) = ______________________ Volume of solution (L)
Practice
You have3.50 L of solution that contains 90.0 g of sodium chloride, NaCl. What is the molarity of that soulution?
Mass of solute 90.0 Solution volume = 3.50 L Molar Mass if NaCl 58.44 g/mol
Molality
Don’t confuse them… The concentration of a solution
expressed in moles of solute per kilogram of solvent
You measure the mass of the solvent…
Formula
moles of solute (mol)Molality = ______________________
mass of solvent (Kg)
Practice
A solution was prepared by dissolving 17.1 g of sucrose C12H22O11 in 125g of water. Find the molal concentration
Given Solute mass = 17.1g sucrose Solvent mass = 125 g H2O
Colligative Properties
Boiling- point elevation Freezing-point depression Vapor-pressure lowering Osmotic pressure
These change in relation to the total number of solute particles present
They are a constant that can be used to calculate the changes in solvents that contain nonvolatile solutes
Electrolytes have greater affects on colligative properties
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