SOLUTIONS
SOLUTIONS
Solution: A solution is a homogeneous mixture where all particles exist as individual molecules or ions.
A solution has two components:
1. Solute
2. Solvent
Solute: The substance being dissolved.
Solvent: The substance which does the dissolving.
Types of Solutions:
1. Saturated: Contains as much solute as solvent
2. Unsaturated: Contains more solvent than solute.
3. Supersaturated: Contains more solute than solvent.
SOLUBILITY
Solubility: The ability of substances to dissolve in a given solvent.
Factors that effect solubility:
1. Temperature:
Higher temperature greater ability for solute to dissolve.
2. Chemical nature: The similar the solute & solvent are; the more soluble the pair will be.
Like dissolves like.
3. Pressure: For gases & liquids increasing pressure increases the solubility
of a gas in a liquid.
Solubility Curve: Shows the dependence of solubility on temperature.
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WHY SOLUTIONS FORM?
What occurs when NaCl dissolves in water?
1. NaCl breaks up into its ions, Na+ & Cl-
2. Cl- ions are attracted to the positive end of water.
3. Na+ ions are attracted to the negative end of water.
4. Due to the attraction the solid dissolves.
5. Like dissolves like.
CONCENTRATION
Refers to the amount of solute contained in a certain amount of solution.
There are several ways to express a solution’s concentration.
1. Volume Percent
2. Weight Percent
3. Weight / Volume Percent
4. Molarity
Volume Percent: Used when the solution is made by mixing two liquids.
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Weight Percent: Measures the amount of solute & solution in grams
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Example 1:
What is the weight percent of glucose in a solution made by dissolving 4.6 g of glucose in 145.2 g of water?
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Weight / Volume Percent: Measures the amount of solute in grams but measures the amount of solution in milliliters.
An example would be a 5%(w/v) NaCl solution. It contains 5 g of NaCl for every 100. mL of solution.
Molarity:
1. The number of moles of solute dissolved in one liter of solution.
2. The units are moles of solute per liter of solution.
3. The units are abbreviated as M.
Example 1:
What is the molarity of a solution which contains 5 g NaCl in 212 mL?
First find the number of moles:
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Example 2:
How many moles of solute are present in 1.5 L of a 0.24 M Na2SO4?
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DILUTION
1. Adding more solvent without the addition of more solute.
2. Moles of solute remain the same.
3. Equation:
M1V1 = M2V2
M=Molarity V=Volume
4. Use equation ONLY when the ratio is 1:1
Example 4:
A chemist starts with 50.0 mL of a 0.40 M NaCl solution and dilutes it to 1000. mL. What is the concentration of NaCl in the new solution?
Use M1V1=M2V2
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