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Accelerated Chemistry Chapter 13 Accelerated Chemistry Chapter 13 notes Chapter 13 Review: 4, 8-12, 20, 22, 23, 27, 28, 29, 30, 34, 39 13.1 Compounds in Aqueous Solution A. Aqueous solution = A solution in which 1. Example: A solution of water (the is the solvent ( ) and NaCl (the ). ) 2. Aqueous solutions can be electrolytes or non electrolytes. a. Electrolytes and non-electrolytes are solutes of solutions. b. Do electrolytes conduct electricity? c. Are non-electrolytes conductors? d. Are all electrolytes conductors? e. Are all conductors electrolytes? CONDUCTORS Pure Substance Mixtures Elements Compounds Alloys Electrolytic Sol’n All metals: Cu, Ag, Fe All ionic compounds in liquid state: NaBr (I), KNO3 (I) Stainless steel, Sterling silver Water solutions of NaBr,HCl, NH3 (aqueous solution) NONCONDUCTORS Pure Substance Mixtures Elements Compounds Non-electrolytic Sol’n All nonmetals: I2, P4 All covalent compounds in liquid state: HBr (I), Al2Cl6 (I), Water solutions of sucrose, isopropyl alcohol, ethyl alcohol, glycerin (aqueous solutions) All solid compounds: Sucrose, NaBr (s), AlBr (s) Ch3 Notes - S Page 1 of 9 Accelerated Chemistry Chapter 13 B. Theory of Ionization Theory of Ionization - Some water solutions conduct solutions are called molecules by the action of the . These from solute . The formation of . Strong electrolytes: NaCl(s) HCl(g) + + H2O(l) H2O(l) Weak electrolyte: HC2H3O2(l) + H2O(l) A arrow shows a strong electrolyte fully producing indicates that the weak electrolyte does not fully . A yield sign . In 1887, Svante Arrhenius (Sweden) proposed the theory of Some substances of changes in . He based his ideas on observations points with different molal concentrations and Note: Some reactions get a arrow ( ) and some get a Arrhenius proposed that when some chemicals are dissolved in particles with . arrow ( , they produce ionic compounds NaCl(s) + MgCl2(s) + acids H2O H2O (covalent dissociation) HCl(g) H2SO4(g) + H2O + H2O Substances that are not Ch3 Notes - S , , or do not dissociate/ionize. Page 2 of 9 ). Accelerated Chemistry Chapter 13 C. Dissociation The separation of ions that occurs when an ionic compound dissolves. 1. A 1.0 M solution of sodium chloride contains: 1 mole of Na+ ions and 1 mole of Cl- ions. NaCl(s) H2O ---------> 1 mole 2. A 1.0 M solution of calcium chloride contains: 1 mole of Ca+2 ions and 2 moles of Cl- ions – a total of 3 moles of ions. CaCl2(s) H2O ---------> 1 mole 3. (a) Dissolve Al2(SO4)3 in water. (b) How many moles of aluminum ions and sulfate ions are produced by dissolving 1 mol of Al2(SO4)3. (c) What is the total number of moles of ions produced by dissolving 1 mol of Al2(SO4)3? (a) Al2(SO4)3(s) H2O ---------> (b) 1 mole ---------> (c) 2 moles Al3+ + 3moles SO42- = of solute ions D. Solubility Equilibria: No ionic compound has No ionic compound has solubility. solubililty. Rough rules of solubililty (using the solubility tables): a. If more than 1 gram per 100g H20 before saturation = b. If .1 gram to 1 gram per 100g H20 = c. If less than .1 gram per 100g H20 = 1. Very slightly soluble ionic compounds – when placed in water, an equilibrium is established between the solid compound and its ions in solution: Example: AgCl(s) Fe(OH)3(s) Ag2S(s) Ch3 Notes - S Page 3 of 9 Accelerated Chemistry Chapter 13 2. Precipitation Reactions = Soluble compounds form Type of rxn: products. - remember – reactants are soluble in water 3. Net ionic equations – double replacement reactions and other reactions of ions in aqueous solutions are represented as ‘net ionic equations.’ Steps: 1. write an equation (molecular equation) 2. write total ionic equation 3. write a net ionic equation – only those compounds and ions that undergo a chemical change in a reaction in an aqueous sol’n and does not include spectator ions (ions found on the reactants and products side). Ex1: Potassium Chloride + Silver nitrate Molecular Equation: Total Ionic Equation: Net Equation: Ex2: Molecular Equation: Total Ionic Equation: Net Equation: Ch3 Notes - S Page 4 of 9 Accelerated Chemistry Chapter 13 15.2 Colligative Properties of Solution Molecular Electrolytes A. Molecular solutes can form electrolytic solutions if they are highly polar. Ionization versus dissociation 1. Dissociation = The separation of that occurs 2. Ionization = The formation of that occurs when a compound dissolves in water (water rips aparts molecules and turns them into ions Ionization example: H2O + HCl When a hydrogen chloride molecule ionizes in water, its hydrogen ion bonds covalently to a water molecule. A ion and a ion are formed. Hydronium Ion: The H+ ion attracts other molecules or ions so strongly that it does not normally exist, so the H+ ion becomes covalently bonded to oxygen. Substances which form electrolytic solutions are: Acids HX HCl, HNO3 Bases MOH NaOH Salts MX NaCl, KBr, CaCO3 H = Hydrogen M = Metal OH = Hydroxide X = NM or P-ion Why? Which of the following form electrolytic solutions? MgBr2 Ch3 Notes - S C8H18 KOH C12H22O11 HNO3 Page 5 of 9 Accelerated Chemistry Chapter 13 Strong vs. weak electrolytes Some compounds ionize/dissociate completely, while others don’t. ( Strong electrolyte – a compound that when dissolved/ionized, yields ) % ions. Distinguishing factor of strong electrolytes – to whatever extent they dissolve in water, they yield only : HCl, HBr and HI are 100% ionized in dilute aqueous solutions. Weak electrolyte – a solute that yields a relatively concentration of ions in an aqueous solution. HF(aq) + H2O(l) In an aqueous solution, the majority of HF molecules are present as dissolved HF s. In general, the extent to which a solute ionizes in solution depends on the bonds within the molecules of the and the strength of attraction to molecules. Note: If the strength of bonds in molecules < the attractive forces of the dipoles, then the covalent bonds break and the molecule separates into . Properties of Electrolyte Solutions Conductivity of Solutions To compare the conductivities of strong and weak electrolytes, the conductivities of solutions of equal concentration must be compared. Ionization of pure water: H2O(l) + H2O(l) So why does water that comes out of the tap conduct electricity? It contains a high enough concentration of dissolved conductor than pure water. Ch3 Notes - S to make it a better Page 6 of 9 Accelerated Chemistry Chapter 13 Colligative Properties of Electrolytic Solutions Properties that depend on the concentration of the solute particles. Freezing point and boiling point are properties. Freezing point depression – the difference between the freezing points of a pure solvent and a nonelectrolyte solution in it. Solutions that conduct electricity contain Ionic compounds : NaCl(s) + H2O(l) yields MgCl2(s) + H2O(l) yields Acids . (dissociation of a covalent compound): HCl(g) + H2O(l) yields H2SO4(l) + H2O(l) yields Substances that are not acids, bases, and salts do not When solutes dissolve in liquids, they . the freezing point. Two factors affect the degree of change in the temperature: the amount of the and the nature of the . ∆tf = kf (m)(x) x = # of produced when the solute dissolves kf water = -1.86 oC/m As the number of solute particles increase, the freezing point . Ex1: Calculate the freezing point of 10.00 grams of NaCl in 200.0 grams of water. Ch3 Notes - S Page 7 of 9 Accelerated Chemistry Chapter 13 Boiling point elevation – when solutes dissolve in liquids, they points. the boiling Same concept as freezing point depression except boiling point . kb water = 0.512 oC/m Why does boiling point elevation occur? The solute takes up space on the of a liquid. This decreases the ability of the liquid to . Thus, the vapor pressure . Boiling occurs when the atmospheric pressure the vapor pressure. So, an in energy is needed to increase the vapor pressure to reach the atmospheric pressure. = solvent versus = solute “A” “B” Which would produce more vapor? Which would have a higher vapor pressure? Which would take less energy to raise the vapor pressure to atmospheric pressure? Which would have a higher boiling point? Ex1: Calculate the boiling point of a solution of 10.00 grams of NaCl in 200.0 grams of water. Ch3 Notes - S Page 8 of 9 Accelerated Chemistry Chapter 13 Ch3 Notes - S Page 9 of 9