Download 6.2 Solution Varieties

Unit 6: Solution Chemistry
Content Outline: Solution Varieties (6.2)
I.
Solutions can be either homogenous (same in composition) or heterogeneous (differing in composition).
II. The 6 Solutions compositions by “states” of matter:
A. Gas into another Gas (such as air… Oxygen gas (O2) dissolved in Nitrogen gas (N2)
B. Gas into a Liquid (such Oxygen or CO2 into blood or CO2 into a soda)
1. Henry’s Law
a. The British Chemist, William Henry in 1803, proposed this law.
b. The law states, “The solubility of an unreactive gas dissolved in a liquid solvent is directly
proportional to the partial pressure of that gas on the surface of that liquid at a constant
temperature.”
Basically it states: If pressure goes up so will the dissolved amount of gas at a constant
temperature.
c. Equilibrium (equal rates)
i.
Amount/rate of a gas entering the solution will equal the amount/rate of gas leaving
the solution. Both processes are occurring at equal rates… hence the term
equilibrium.
ii.
If pressure on the gas increases, then the amount/rate of dissolving into the solution
will increase.
iii.
If the amount/rate of dissolving into the solution increases, the amount/rate of gas
leaving the solution increases.
iv.
Until a new equilibrium is established between the gas and liquid at the surface.
d. Effervescence (“fizzing”)
i.
This is the rapid release of a dissolved gas from a solvent liquid.
For example: the fizzing sound and small gas bubbles leaving your soft drink when
you open it. Keeping the lid on helps your soda not go flat as the gas cannot escape
into the air. The gas is CO2.
ii.
Adding Kinetic energy in the form of heat or shaking will increase the effervescence
(by making the gas less soluble in the liquid).
Gas molecules moving faster (greater Kinetic energy), makes it easier for them to
escape the liquid’s attractive forces.
C. Liquid into another Liquid (Such as an alcohol into water)
1. Miscible
a. This term refers to a liquid being freely dissolvable, in any proportion, to another liquid.
2. Immiscible
a. This term refers to a liquid that will not dissolve into another liquid.
Like dissolves like… not different.
Polar liquids dissolve other polar liquids.
Non-polar liquids dissolve other non-polar liquids.
Polar liquids do not dissolve non-polar…for example water and oil.
How do you clean greasy dishes and pan with water? You use colored highly concentrated salt
water (dish washing soap). The salt ions act as a “connection” between the two substances.
D. Solid into a Liquid (Such sugar or salt into water)
1. Homogenous (Pure)
a. Equal distribution of the solid throughout giving it the same chemical properties and
composition.
b. To separate the two would require heating (evaporating) one out, like the water.
2. Suspension
a. This term refers to a heterogeneous solution with particles that are too big so that the liquid
cannot suspend them. Gravity “drags” them to the bottom of the container.
b. Agitating (“stirring”) can resuspend them for a short period of time.
Why you want to shake or stir Italian dressing before you put it on your salad? So you get
the good spices and not just oil.
c. Can be separated by filtering.
3. Colloid
a. A heterogeneous solution with particle of intermediate size in comparison to Pure solutions
and Suspensions.
b. They will appear to be homogenous (dispersed phase), but over time gravity will separate
the particles into differing layers based upon molecular density.
c. Milk is a good example. If left undisturbed, the proteins and sugars will separate into
different layers. Why you should always shake your milk before pouring or drinking in the
carton?
d. Colloids can display what is called the Tyndall Effect
 John Tyndall, an Irish Physicist, proposed in 1850.
i.
The scattering of light passing through because of the moving suspended particles.
It appears “hazy” instead of clear like water.
ii.
This effect is used to tell the difference between a true solution and a colloid.
iii.
The motion of the rapidly moving particles is called Brownian Motion.
 Robert Brown, British Botanist proposed in 1827.
e. Can be separated by complex filtering or by putting it in a centrifuge (“spinner”).
4. Electrolytes & Non-Electrolytes
a. Electrolytes – Solid dissolves into ions. The ions allow electricity (flowing electrons) to be
conducted through the solution. For example: salt in water.
b. Non-electrolytes – Solid does not create ions. So there is no ability to conduct electricity.
For example: sugar in water.
c. Hydration Shell – the surrounding of ions by water molecules using Hydrogen Bonds in
between them.
d. Hydrates - dried Ionic crystals that contain water.
α. These are written chemically like the following: CuSO4* 5 H2O – called Copper (II) Sulfate
Penta-hydrate.
E. Liquid into a solid (not common but an example is the material used to fill teeth cavities, called
Dental Amalgam)
F. Solid into a solid
1. Must be in the molten (super-cooled) phase so as to mix uniformly. These “blended” metals are
called alloys.
a. They have a mixture of chemical properties of the composing metals.
b. Can be separated by heating to the different melting points of each metal.