Properties of Solutions Solution: Homogenous mixture of 2 or more substances; particles are small...
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Transcript of Properties of Solutions Solution: Homogenous mixture of 2 or more substances; particles are small...
![Page 1: Properties of Solutions Solution: Homogenous mixture of 2 or more substances; particles are small (transparent) Colloid: Homogenous mixture of 2 or more.](https://reader035.fdocuments.in/reader035/viewer/2022062713/56649f465503460f94c67aaf/html5/thumbnails/1.jpg)
Properties of Solutions
Solution: Homogenous mixture of 2 or more substances; particles are small (transparent)
Colloid: Homogenous mixture of 2 or more substances; particles are larger (opaque)
Solutions can be liquid, solid or gaseous
Examples: Ocean, sugar water
Gold alloy
Air, humid oxygen
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Solvent: Substance present in a solution in the greatest amount
Example: Water in the ocean; nitrogen in air
Solute: Substance present in a solution in lesser amounts than the solvent
Example: Salt in ocean; oxygen in air
Solutes can be electrolytes or nonelectrolytes
Electrolytes: solutes that dissociate in solution into ions that carry charge (ionic compounds)
Nonelectrolytes: solutes that do not dissociate in solution, and do not carry any charge
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Solubility
Soluble substance: Substance that is able to dissolve in a solvent
Insoluble substance: Substance that does not dissolve in a solvent
Solubility: Maximum amount of solute that can be dissolved in a specific amount of solvent under specific conditions of temperature and pressure (g solute/100 mL solution)
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Saturated Solution: Solution containing maximum amount of solute that will dissolve under current conditions
Unsaturated Solution: Solution containing less than the maximum amount of solute that will dissolve under current conditions
Supersaturated Solution: Unstable solution containing amount of solute greater than the solubility value
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General Rules for the Solubility of Ionic Compounds
•A compound is soluble if it contains one of the following cations:
-Group 1A cations: Li+, Na+, K+, Rb+, Cs+
-Ammonium, NH4+
•A compound is soluble if it contains one of the following anions:
-Halide: Cl-, Br-, I-, except for salts with Ag+, Hg22+, Pb+2
-Nitrate, NO3-
-Acetate, CH3CO2-
-Sulfate, SO42-, except for salts with Ba+2, Hg2
2+, Pb+2
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Solubility of Solids and Liquids vs. Gases
•Solubility of liquids and solids in water increases with increasing temperature
Example: More sugar will dissolve in warm water than in cold water
•Solubility of gases in water decreases with temperature
•Solubility of gases in water increases with increasing pressure (Henry’s Law)
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“Like dissolves like:”
polar solvents will dissolve polar solutes
nonpolar solvents will dissolve nonpolar solutes
Examples: wax in CCl4, sugar in water; oil in water?
Solutes fail to dissolve when:
1) forces between solute particles out-weigh attractions between solute and solvent
2) solvent particles are more attracted to each other than to solute
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Examples of Like Dissolves Like
Solvents Solutes
Water (polar) Ni(NO3)2
(ionic)
CH2Cl2 (nonpolar)
I2 (nonpolar)
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Solutes dissolve faster when:
Concentration: Relationship between amount of solute contained in a specific amount of solution
Solute particles are small
Solvent is heated
Solution is stirred
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Concentration as Percent
Percent: Solution concentration giving the amount of solute in 100 parts of solution
% = part/total x 100
Weight/weight percent: Concentration giving the mass of solute in 100 mass units of solution
%(w/w) = solute mass/solution mass x 100
Example: 12.0%(w/w) sugar solution
12 g sugar per 100 g solution
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Weight/volume percent: Concentration giving the grams of solute contained in 100 mL of solution
%(w/v) = grams solute/mL solution x 100
Example: 12.0%(w/v) sugar solution
12 g sugar per 100 mL solution
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Molarity: Unit of concentration used with solutions; number of moles of solute per liter of solution
Molarity (M) = moles of solute/liters of solution
Examples: 2 moles of NaCl dissolved in 1 L of water
M = 2 moles/1 L = 2 M
1.5 moles NaCl dissolved in 2 L of water:
M = 1.50 moles/2.00 L = .750 M
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Dilution
Dilution: addition of solvent to decrease theconcentration of solute. The solution volume changes,but the amount of solute is constant.
moles of solute (mol) = molarity (M) x volume (V)
initial values final values
M1V1 = M2V2
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M1 V1 =M2 V2
Practice Problem: Prepare 250 mL of 0.100 M NaCl solution from a 2.00 M NaCl solution.
M1 = molarity of starting solution (in this case 2.00M NaCl)
V1 = volume of starting solution required (always unknown)
M2 = molarity of final solution after dilution (in this case 0.100M NaCl)
V2 = volume of final solution, after dilution (in this case 250ml)
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Prepare 250 mL of 0.100 M NaCl solution from a 2.00 M NaCl solution.
M1 = molarity of starting solution (in this case 2.00M NaCl)
V1 = volume of starting solution required (always unknown)
M2 = molarity of final solution after dilution (in this case 0.100M NaCl)
V2 = volume of final solution, after dilution (in this case 250ml)
M1 V1 =M2 V2
V1 = M2 V2 / M1
V1 = (0.100M) x (250 ml) / (2.00M) = 12.5ml
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Osmotic Pressure
Osmosis: Movement of water through a semipermeable membrane, from more dilute solution towards more concentrated solution
Osmotic pressure: amount of pressure required to stop flow of water due to osmosis
Isotonic solutions: solutions with identical osmotic pressure; no urge for water to flow
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4% starch
10% starch
H2O
Example:
During osmosis, water flows across the semi-permeable membrane from the 4% starch solution into the 10% solution.
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Eventually, the flow of water across the semi-permeable membrane becomes equal in both directions.
7% starch
7% starch
H2O
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Hypotonic solution: the more dilute of 2 solutions separated by a semipermeable membrane; water leaves this solution and flows across membrane to the more concentrated solution
Hypertonic solutions: the more concentrated of 2 solutions separated by a semipermeable membrane; water enters this solution, moving across the membrane from the more dilute solution
Crenate Burst No Change
(hypertonic) (hypotonic) (isotonic)