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Chapter 8 Solutions Solution = a Homogeneous Mixture
of 2 or more Substances Solvent: the component present in the greatest amount Solute: the component present in a smaller amount Aqueous Solution: Water is the Solvent
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Not all Solutions are Liquids:
Metal alloys (brass, yellow gold, bronze) are solid solutions Air is a gaseous solution
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Water as a Solvent Water is polar Water forms Hydrogen bonds
polar & ionic compounds dissolve in water Water forms Hydrogen bonds -with other water molecules -with other molecules that can H-bond
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Solubility “Like dissolves like” a qualitative statement of solubility
-polar solutes: -nonpolar solutes: Degree of Solubility a quantitative assessment of solubility Temperature dependent -solids: -gases: Pressure dependent
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Effect of Temperature on Solubility
Effect of Pressure on Solubility Henry’s Law: as the pressure above a liquid increases, the solubility of the gas increases.
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Solubility Saturated Solution Supersaturated Solution Dilute Solution
-contains the maximum amount of solute Supersaturated Solution -unstable solution containing more solute than “allowed” Dilute Solution -contains a small amount of solute relative to the maximum Concentrated Solution -contains a large amount of solute sodium acetate demo
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Electrolytes & Nonelectrolytes
Electrolytes - dissociate into ions when dissolved in water Strong Electrolytes – are 100% dissociated Weak Electrolytes – only partially dissociated Nonelectrolytes – do not produce ions
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Water-soluble salts: Li+, Na+,K+, NH4+ All NO3-, C2H3O All Cl-, Br- , I All except Ag+, Hg+, Pb2+ SO All except Ca, Sr, Ba, Hg, Pb, Ag Water-insoluble salts: CO32-, PO43- All except Group IA metals and NH4+ OH- All except Group IA metals (Ca2+, Sr2+, Ba2+ are slightly soluble) S2- All except Groups IA & IIA metals and NH4+
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K2SO3 HNO3 Al(C2H3O2) 3 Ba3(PO4) 2 HClO4
Check the Solubility Rules—are the following compounds soluble in water? Write equations for their dissociation: K2SO3 HNO3 Al(C2H3O2) 3 Ba3(PO4) 2 HClO4 Dissociation of ionic compound animation:
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Solution Concentrations
Concentration Based on Mass/Volume: %(w/v) = grams solute x 100 ml solution Concentration Based on Mass/Mass: %(w/w) = grams solute x 100 grams solution
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Concentration Based on Moles/Volume: Molarity M = moles of solute
Liters of solution Sample Problems: Find the Molarity of a solution that contains 5.0 x 10-2 moles of NaOH dissolved in 0.25 Liters of solution. Find the Molarity of a solution that contains 12.5 grams FeCl3 dissolved in 750 mL of solution.
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Using Molarity as a Conversion Factor
Sample Problems: How many liters of 2.00M NaCl are needed to provide 1.75 mole of NaCl? How many moles of NaOH are in 125 mL of a 0.211M solution of NaOH? M x V = moles
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More practice: Calculate the %(m/v) of a solution that contains 25 grams of glucose in 525 mL. What volume of 4.8%(m/v) glucose solution contains 5.3 grams of glucose? How many grams of glucose are needed to make 1.0Liter of 3.0%(m/v) solution?
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More practice: Find the molarity of a solution that contains 2.5 x 10-2 moles of NaCl in Liter. Find the molarity of a solution that contains 25 grams of NaCl in Liter. Find the molarity of a solution that contains 25 grams of glucose in 525 mL.
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More practice: How many moles of NaCl are in 2.0 Liters of 0.10M NaCl solution? How many moles of glucose are in 25.0 mL of 0.265M glucose solution? What volume of 0.265M glucose contains mole of glucose?
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Suspensions: mixtures with larger particles
Liquid Solutions: -clear & transparent -colorless or colored Colloids: solute particles are large enough to scatter light particles (>1nm) -true solutions do not scatter light -colloids are solutions that do not settle out -examples: fog, smoke, whipped cream, mayonnaise, gelatin Suspensions: mixtures with larger particles -suspensions will settle -particles can be filtered out -examples: muddy water, calamine lotion
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Colligative Properties: Concentration-Dependent Solution Properties
vapor pressure lowering - boiling point elevation freezing point depression 4. Osmotic pressure
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Osmotic pressure: the amount of pressure required to stop the flow of solvent through a membrane.
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Two aqueous solutions are separated by a
semipermeable membrane.
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Isotonic Solutions – same osmotic pressure
Hypotonic Solutions — lower solute concentration Hypertonic Solutions — higher solute concentration How Osmosis works
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Concentration-Dependent solution properties:
-are proportional to the concentration of solute particles -strong electrolytes give more particles in solution solute type molarity osmolarity freezing pt boiling pt
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Double Replacement Reactions/Precipitation
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Neutralization
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Titration: Acid + Base Salt + Water Equivalence Point = Endpoint =
A volumetric analysis technique used to find the concentration of something in solution frequently used for Acid-Base (Neutralization) Reactions Acid + Base Salt + Water Equivalence Point = Endpoint =
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At the Equivalence Point: MA x VA = MB x VB
(given that the molar ratio of acid-to-base is 1 to 1) Example: A 20.0 mL sample of HCl was titrated to an equivalence point with 41.6 mL of 0.165M NaOH. What is the Molarity of the acid? Example: A 42.6 ml sample of vinegar (acetic acid solution) is titrated with 26.5 ml of 0.055M NaOH. What is the Molarity of the acid?
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