Solutions

Solutions

I.
Solutions

A. Definition: mixtures that appear homogeneous.
Made of very small particles that are in fact, individual molecules, atoms or ions.

1. Dissolved particles (SOLUTE) are distributed evenly among the particles of the SOLVENT.

2. SOLUTE won’t come out of SOLUTION.

3. SOLUTION is clear and transparent (not necessarily colorless).

4. Particles of SOLUTE are to small to be filtered.

5. SOLUTE takes the phase of the SOLVENT.

C. Colloidal Dispersion: Particles are larger than in a solution but still don’t settle out – a beam of light increases width as it passes through.

D. Suspension: particles larger than colloidal dispersion and will settle out –a beam of light won’t pass through.

A. Definitions
	Solute: thing being dissolved
	Solvent: thing dissolved in
	Solution: combination of solute and solvent
	Miscible: will dissolve
	Immiscible: won’t dissolve
	Precipitate: solid the comes out of solution

B. Factors affecting solubility
1. Nature of solute and solvent “Like Dissolves Like”- to substances will be miscible if they have same type of bond. ionic tends to be the fastest
2. Temperature Solids/ Liquids – as temp increases, solubility increases Gases – as temp increases, solubility decreases

3. Pressure Solids/ Liquids – NO EFFECT Gases – as pressure increases, solubility increases

C. Factors affecting Rate of Solution (how fast it dissolves)
1. Size of Particles – small particles mean greater surface area therefor higher rate.

2. Stirring - stirring will increase the rate at which a substance dissolves.
3. Temperature – as before, adjusting the temperature will effect the rate of solution by increasing or decreasing the amount that can dissolve at the given temperature.
Solids/ Liquids – as temp increases, rate increases Gases – as temp increases, rate decreases
4. Amount of Solute already dissolved – if the solution is “crowded” with solute it will slow the rate at which more solute can dissolve.

E. Solubility Guidelines – Reference Table F
Tells us compounds that are soluble.

Table F

Solubility Guidelines for Aqueous Solutions

*Ions That Form Soluble* Compounds**	Exceptions
Group 1 ions (Li+, Na+, etc.)
ammonium (NH4+)
nitrate (NO3-)
Acetate (C2H3O2- or CH3COO-)
hydrogen carbonate (HCO3-)
chlorate (ClO3-)
perchlorate (ClO4-)
halides (Cl-, Br-, I-)	when combined with Ag+, Pb2+, and Hg22+
sulfates (SO42-)	when combined with Ag+, Ca2+, Sr2+, Ba2+, and Pb2+

*Ions That Form Insoluble* Compounds**	Exceptions
carbonate (CO32-)	when combined with Group1 ions or ammonium (NH4+)
chromate (CrO42-)	when combined with Group1 ions, Ca2+, Mg2+, or ammonium (NH4+)
phosphate (PO43-)	when combined with Group1 ions or ammonium (NH4+)
sulfide (S2-)	when combined with Group1 ions or ammonium (NH4+)
hydroxide (OH-)	when combined with Group1 ions, Ca2+, Ba2+, Sr2+, or ammonium (NH4+)

The substances listed on the left of each of the above tables are always soluble (blue) or insoluble (purple) in water. The exceptions to these rules are listed to the right of the substance.

Example: Any compound that contains the sulfate ion (SO42-) will be soluble in water except Ag2SO4, CaSO4, BaSO4, and PbSO4

F. Saturation
terms that define the ratio of solute to solvent based on maximum capacity in the solution
	1. Unsaturated – the solution can hold more solute than it is at that temperature. A point under the curve
	2. Saturated – the solution holding exactly what it is capable of at that temperature. A point on the curve
	3. Supersaturated – the solution is holding more solute than typically capable at that temperature. A point above the curve
	How? – The solution is heated so that it can hold more, then as it cools the solute stays in the solution if it is not disturbed.

III.

Effect of Solute on Solvent

A. Freezing Point Depression
a solute dissolved in a solvent will lower the temperature at which it freezes.
The more solute the lower the freezing point.

B. Boiling Point Elevation
a solute dissolved in a solvent will raise the temperature at which it boils.
The more solute the higher the boiling point.

Concentration

A. Molarity(M)

The concentration of a solution based on the number
of moles of solute dissolved in a given amount of solution.

Expressed as moles per liter or a molar solution.

Molarity =

Moles of Solute

Liters of Solution

Example: If 3 moles of NaCl are dissolved in 0.5 liters of water, the calculation would be as follows:
Molarity =	3 moles 0.5 liters	= 6 moles/liter

B. Parts per Million (ppm)

The concentration of a solution based on the number
of grams of solute dissolved in a given mass of solution.

Typically used for very small amounts.

parts per million=

grams of solute

grams of solution

X 1,000,000

Example: A 1000 gram solution is found to contain 25 grams of KBr.
What is the concentration in parts per million?

parts per million=

25 grams

1000 grams

X 1,000,000

= 25,000 ppm

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Last Revised May 9, 2007