C4_AQ_rxns_fillin1.pdf - Chapter 4 1 Solutions \u2022 Solution \u2013 \u2022 Solvent \u2013 \u2022 Solute \u2013 2 3 Preparation of a solution Solubility Solubility

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Unformatted text preview: Chapter 4 1 Solutions • Solution – • Solvent – • Solute – 2 3 Preparation of a solution Solubility Solubility depends on: Temperature For gases in liquids: For solids and liquids: Pressure Henry’s Law: Mathematically: Henry’s law applies best when 4 Solution Terms Saturated solutionUnsaturated solution – Supersaturated solution – Hydrated ionSolvated ion – 5 Rate of dissolution Rate of reaction determined by 1 Chapter 4 6 Concentration: Mass percentage – Volume percentage – Parts per million (ppm) – Molarity (M) – Millimolar (mM) – Molality (m) – Mole fraction of A Normality- 7 Concentration example Sodium carbonate (MM 106.0 g/mol) is a base which is sold commercially as aqueous solution that is 10.0% sodium carbonate by mass. The solution has a density of 1.10 g/mL. The density of water is 0.997 g/mL. Determine its concentration in the following units. (a) g solute/L soln (b) Mole fraction (c) Molarity (d) molality 2 Chapter 4 8 Concentration Stoichiometry The reaction that occurs when current is drawn from a lead storage battery is described by the following equation: Pb(s) +PbO2(s) + 2 H2SO4(aq) 2PbSO4(s) + 2H2O(l) What volume of 0.500 M H2SO4 solution is required to produce 10.0 g of PbSO4(MM: 303.26 g/mol)? 9 Electrical Conductivity of Aqueous Solutions 10 Electrolytes • Electrolytes: • Strong Electrolytes – • Strong Electrolytes – • Weak Electrolytes – • Nonelectrolytes – 11 Aqueous Solution process 12 Concentration of Ions What is the concentration of Cl ions for a 0.25 M CaCl2 solution: CaCl2(s)→ Ca2+(aq)+ 2Cl–(aq) Ca2+: Cl–: Concentration of ions in solution: 3 Chapter 4 13 Dilution • The process of • Dilution with water does not alter the numbers of • of solute before dilution = Mathematically: present. after dilution 14 Dilution What is the minimum volume of a 2.00 M NaOH solution needed to make 150.0 mL of a 0.800 M NaOH solution? 15 Types of reactions in Aqueous Solution • Precipitation reactions • Acid-base reactions • Oxidation-reduction reactions 16 Precipitation Reactions • Rules of solubility control what happens • A solid 1. Writing solution chemistry reactions 2. Solubility rules 3. Net ionic equations 4. Solution chemistry stoichiometry 29 Formula Equation (Molecular Equation) AgNO3(aq) + NaCl(aq) → AgCl(s) + NaNO3(aq) 30 Complete Ionic Equation Ag+(aq) + NO3-(aq) + Na+(aq) + Cl-(aq) → AgCl(s) + Na+(aq) + NO3-(aq) 31 Net Ionic Equation Ag+(aq) + Cl - (aq) → AgCl(s) 4 Chapter 4 Example: K2CrO4(aq) and Ba(NO3)2(aq) Formula equation Complete ionic equation Net ionic equation 25 26 Precipitates • Soluble – • Insoluble – • • Insoluble and slightly soluble are often used interchangeably. Soluble and marginally soluble are often used interchangeably. Simple Rules for Solubility – Table 4-2 in text 1. Most nitrate (NO3-) salts are soluble. 2. Most alkali metal (group 1A) salts and NH4+ are soluble. 3. Most Cl-, Br-, and I- salts are soluble (except Ag+, Pb2+, Hg22+). 4. Most sulfate salts are soluble (except BaSO4, PbSO4, Hg2SO4, CaSO4). 5. Most OH- are only slightly soluble (NaOH, KOH are soluble, Ba(OH)2, Ca(OH)2 are (marginally) soluble). 6. Most S2-, CO32-, CrO42-, PO43- salts are only slightly soluble, except for those containing the cations in Rule 2. 32 Chemical Equations Write the correct formula equation, complete ionic equation, and net ionic equation for the reaction between cobalt(II) chloride and sodium hydroxide. 5 Chapter 4 33 Solving Stoichiometry Problems for Reactions in Solution 1. Identify the species present in the combined solution, and determine what reaction if any occurs. 2. Write the balanced net ionic equation for the reaction. 3. Calculate the moles of reactants. 4. Determine which reactant is limiting. 5. Calculate the moles of product(s), as required. 6. Convert to grams or other units, as required. 34 Solution Stoichiometry 1 10.0 mL of a 0.30 M sodium phosphate solution reacts with 20.0 mL of a 0.20 M lead(II) nitrate solution (assume no volume change). What precipitate will form? What mass of precipitate will form? What is the concentration of nitrate ions left in solution after the reaction is complete? What is the concentration of phosphate ions left in solution after the reaction is complete? 39 5 Chapter 4 39 Acid and Bases • Arrhenius Acids Bases HCl(aq) + NaOH(aq) NaCl(aq) + HOH(l) Net ionic equation: • Too limiting because we would like to work with bases besides OH40 Acid–Base Reactions (Brønsted–Lowry) • Acid— • Base— NH3(aq) + HNO3(aq) NH4+(aq) + NO3-(aq) 41 Performing Calculations for Acid–Base Reactions 1. List the species present in the combined solution before any reaction occurs, and decide what reaction will occur. 2. Write the balanced net ionic equation for this reaction. 3. Calculate moles of reactants. 4. Determine the limiting reactant, where appropriate. 5. Calculate the moles of the required reactant or product. 6. Convert to grams or volume (of solution), as required. 42 Acid–Base Titrations • Quantitative analysis of acid base chemistry • Titration – analyte – 43 • Equivalence point – • Endpoint – Acid-base titration For the titration of sulfuric acid (H2SO4) with sodium hydroxide (NaOH), how many moles of sodium hydroxide would be required to react with 1.00 L of 0.500 M sulfuric acid to reach the endpoint? 6 Chapter 4 44 Oxidation-Reduction Reactions • Redox reaction – Oxidation – Reduction – Oxidation and Reduction must occur Oxidizing agent – Reducing agent – 51 Rules for Assigning Oxidation States 1. Oxidation state of an atom in an element = 0 2. Oxidation state of monatomic ion = charge of the ion 3. Oxygen = ・2 in covalent compounds (except in peroxides where it = ・1) 4. Hydrogen = +1 in covalent compounds 5. Fluorine = ・1 in compounds 6. Sum of oxidation states = 0 in compounds 7. Sum of oxidation states = charge of the ion in ions Oxidation states Find the oxidation states for each of the elements in each of the following compounds: K2Cr2O7 PCl5 52 CO32- SF4 MnO2 7 ...
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