aqueous reactions and solution stoichiometry
DESCRIPTION
Aqueous Reactions and Solution Stoichiometry. Aqueous Solutions. Solutions in which water is the dissolving medium. Water Molecule. Hydrogen Bonds. High surface tension Low vapor pressure High specific heat capacity High heat of vaporization High boiling point. - PowerPoint PPT PresentationTRANSCRIPT
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