Properties of Water Resulting from Hydrogen Bonding
• High surface tension• Low vapor pressure• High specific heat
capacity• High heat of vaporization• High boiling point
Solvents and Solutes
• Aqueous Solutions: Water samples containing dissolved substances
• Solute: the dissolved particles• Solvent: The medium the particles dissolve in• Solutions are homogeneous mixtures• Solutes can be solids, liquids or gases- ionic or
molecular
Like Dissolves Like
• Solvation: the process that occurs when a solute dissolves
• H2O and NaCl
• H2O and Oil
Factors that affect Solubility
• Nature of the solvent and solute• Agitation (stirring)• Temperature• Surface Area
Temperature• The higher the
temperature the higher the solubility
• Higher temperatures= greater kinetic energy = increased frequency of collisions between solute and solvent
Surface Area
• Fine powders will dissolve more rapidly than large crystals
• Dissolving is a surface phenomenon• More surface = faster dissolution
Solubility
• Is the amount of a substance that dissolves in a given quantity of a solvent at a given temperature
Saturated Solution
• A solution that contains the maximum amount of solute for a given amount of solvent at a constant temperature
Solubility of liquids
• Miscible: Two liquids that dissolve in each other (i.e. Ethanol and water)
• Immiscible: two liquids that are completely insoluble (i.e. Oil and water)
Concentration
• Concentration of a solution is expressed as the amount of solute dissolved in an amount of solution
• Dilute solution: contains a low concentration of solute
• Concentrated Solution: contains a high concentration of solute
Molarity
• Molarity (M) is the number of moles of solute dissolved per liter of solution
• Volume is the total volume of the solution, NOT the volume of the solvent alone
Example
• A solution has a volume of 250 mL and contains 0.70 mol NaCl. What is the molarity of the solution?
• Molarity (M) = Moles of solute Liter of solution
Example
• A solution has a volume of 2.0 L and contains 36.0 g of glucose. If the molar mass of glucose is 180 g/mol what is the molarity of the solution?
Molarity (M) = Moles of solute Liter of solution
Making Dilutions
• You can make a solution less concentrated by diluting it with solvent
• The dilution reduces the moles of solute per unit volume
• Total moles of solute does not change• Moles of solute = moles of solute before dilution after dilution
Example
• How many milliliters of a stock solution of 4.00 M KI would you need to prepare 250.0 mL of 0.760 M KI?
• M1V1=M2V2
Electrolytes and Nonelctrolytes• Electrolytes:
compounds that conduct electricity in aqueous solution or molten state
• ALL Ionic compounds are electrolytes
• Not all conduct to the same degree
• Nonelectrolytes: don’t conduct
Acids
• Give food a sour flavor• Aqueous solutions of acids are electrolytes• React with compounds containing hydroxide
ions to form salt and water
Formulas of Acids
• An acid produces hydrogen ions- generic acid HX (X is an ion)
• IE– HCl– H2SO4
– HNO3
Common Monoprotic Acids
HCl Hydrochloric Acid
HF Hydrofluoric Acid
HNO3 Nitric Acid
CH3COOH Acetic Acid
Strong Acids
• Strong acids are completely ionized in an aqueous solution
• Hydrochloric Acid• Sulfuric Acid
• HCl (g) + H2O (l) H3O+ (aq) + Cl- (aq)
Weak Acids
• Weak acids ionize only slightly in aqueous solution, ionization is not complete
• CH3COOH (aq) + H2O H3O+(aq) + CH3COO- (aq)
• Ethanoic Acid Ethonate ion <1%
Bases
• Feel slippery• Taste bitter• Are electrolytes• React with acids to form water and salt
Strong Bases
• Strong bases dissociate completely into metal ions and hydroxide ions in aqueous solutions
• ALL bases containing OH- ions are strong bases
Weak Bases
• Weak bases react with water to form the hydroxide ion and the conjugate acid of the base
• NH3 (aq) + H2O (l) NH4+ (aq) + OH- (aq)
• <1%
Titration
• The concentration of an acid (or base) in a solution can be determined by performing a neutralization reaction
Steps for Titration
• Measured volumes of a base of known concentration are mixed into the acid until the indicator barely changes color
Titration
• HCl (aq) + NaOH (aq) H2O (l) + NaCl (aq)
• 1 mol 1 mol 1 mol 1mol
• H2SO4 (aq) + 2KOH (aq) 2H2O (l) + K2SO4 (aq)
• 1 mol 2 mol 2 mol 1 mol
Example
• How many milliliters of 0.45 M hydrochloric acid must be added to 25.0 mL of 1.00 M potassium hydroxide to make a neutral solution?
Example
How many milliliters of 0.45 M hydrochloric acid must be added to 25.0 mL of 1.00 M potassium hydroxide to make a neutral solution?
HCL (aq) + KOH (aq) H2O (l) + KCl (aq)
25.0mLKOH =.0250 L KOH x1.00 mol =0.0250 mol KOH 1L0.025 mol KOH x 1 mol HCl x 1 L HCl = .0556 L HCl 1 mol KOH 0.45 mol HCl
Oxidation
• Originally meant: the combination of an element with oxygen to produce oxides
2Fe (s) + 3O2 (g) FeO2 (s)
Redox Reactions
• Oxidation-reduction Reactions• Oxidation is loss of electrons or gain of oxygen• Reduction is gain of electrons or loss of
oxygen
Redox Reactions
• Mg + S Mg 2+ + S 2-
• Magnesium Sulfur Magnesium Sulfur
• Atom Atom Ion Ion
• Mg Mg 2+ + 2 e- (Loses 2 e-) oxidized• S S 2- (gains 2 e-) reduced
+
• Reducing Agent: the substance that loses electrons
• Oxidizing Agent: The substance that gains electrons
• Mg + S MgS
Oxidized
Reduced
Reducing Agent
Oxidizing Agent
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