Types of Chemical Reactions and Solution StoichiometryChapter 4
Section 4.1 Water, the Common Solvent
Nature of Water • Type of bond? • Shape? • Polarity? Covalent Bent/Angular Polar
Ionic Solute-Solvent Interaction • Ionic solids that dissolve are soluble. • Ionic solids will dissolve in polar solvents but not nonpolar solvents • Water molecules break the crystal lattice into separate ions. This is dissociation. • Then the water molecules surround the ions. This is hydration. • Ionic solids that do not dissolve are insoluble.
Solubility of Compounds notes
Solubility of Compounds notes
Liquid Solute-Solvent Interaction • Miscible – Liquids that dissolve freely in one another in any proportion. • Immiscible – Liquids that are not soluble in each other. • “Likes dissolve likes” Polar solutes dissolve in polar solvents. Nonpolar solutes dissolve in nonpolar solvents. • Alcohols are slightly polar.
Immiscible & Miscible p. 412
Section 4.2 The Nature of Aqueous Solutions
Solution • A homogeneous mixture of two or more substances in a single phase • Particles are thoroughly mixed and remains mixed indefinitely • Components of a solution • Solvent: does the dissolving; the larger amount • Solute: is being dissolved; the smaller amount
Electrolytes & Nonelectrolytes • Electrolyte – a substance that dissolves in water to give a solution that conducts electric current • Nonelectrolytes • a substance that dissolves in water to give a solution that does not conduct electricity • Does not produce ions • Example: sugar and ethanol
Strong Electrolytes • Completely ionized when they are dissolved in water • Three classes • Soluble Salts • Strong Acids: produce H+ ions when dissolved in water • HCl (g) + H2O (l) H3O+(aq) + Cl-(aq) • Strong Bases: produce OH- ions when dissolved in water • NaOH (s) Na+(aq) + OH-(aq) NaCl (s) Na1+(aq)+ Cl1-(aq)
Strong Acids • An acid that ionizes completely in aqueous solution. • STRONG ACID LIST • HCl hydrochloric acid • HI hydroiodic acid • HBr hydrobromic acid • H2SO4 sulfuric acid • HNO3 nitric acid • HClO3 chloric acid • HClO4 perchloric acid MEMORIZE!
Strong Bases • Strong Bases – bases that dissociate completely – strong electrolytes • Formed from Group I & II metalscombined with hydroxide
Weak Electrolytes • Substances that exhibit a small degree of ionization in water • Two classes • Weak Acids: produce few H+ ions when dissolved in water CH3COOH(aq)+ H2O(l) CH3COO-(aq) + H3O+(aq) • Weak Bases: produce few OH- ions when dissolved in water NH3 (aq) + H2O (l) NH4+(aq) + OH-(aq)
Section 4.3 The Composition of Solutions
mol M = L Molarity The number of moles of solute in one liter of solution. moles of solute M = liters of solution
Molarity Practice Problems • Calculate the molarity of a solution prepared by dissolving 11.5 g of solid NaOH in enough water to make 1.50 L of solution. • Give the concentrations of each type of ion in the following solutions: • 0.50 M Co(NO3)2 • 1 M Fe(ClO4)3 • Calculate the number of moles of chloride ions in 1.75 L of 1.0 x 10-3 M ZnCl2. • Typical blood serum is about 0.14 M NaCl. What volume of blood contains 1.0 mg NaCl?
Standard Solution • A solution whose concentration is accurately known. • To analyze the alcohol content of a certain wine, a chemist needs 1.00 L of an aqueous 0.200 M K2Cr2O7 solution. How much solid potassium dichromate must be weighed out to make this solution?
Dilution • A solution in concentrated form. • Dilution: process where water is added to achieve the molarity desired for a particular solution. • If the mole ratio is 1:1, then M1V1=M2V2 can be used • What volume of 16 M sulfuric acid must be used to prepare 1.5 L of a 0.10 M sulfuric acid solution?
Section 4.5 Precipitation Reactions
Precipitation Reactions • Two solutions mix and an insoluble solid forms • The solid that forms is called a precipitate. • Predicting Reaction Products: • Using the solubility rules, predict what will happen when the following pairs of solutions are mixed. • Potassium nitrate and barium chloride • Sodium sulfate and lead (II) nitrate • Potassium hydroxide and iron (III) nitrate
Section 4.6 Describing Reactions in Solution
NET IONIC EQUATION • Write the balanced equation for the reaction between ammonium sulfide and cadmium II nitrate. Be sure to include states of matter • What type of reaction is it? What are the products? (NH4)2S (aq) + Cd(NO3)2 (aq) 2 NH4NO3(aq) + CdS (s)
NET IONIC EQUATION (NH4)2S (aq) + Cd(NO3)2 (aq) 2 NH4NO3(aq) + CdS (s) Each (aq) is dissociated. The (s) is not dissociated; it is the precipitate.
NET IONIC EQUATION Cd NH4 (NH4)2S (aq) + Cd(NO3)2 (aq) 2 NH4NO3(aq) + CdS (s) (NH4) S (NO3) NO3 CdS 1+ 1+ 2- 1- 1- 2+ 2 2 + + + 2 + + 2 (s) (aq) (aq) (aq) (aq) (aq) (aq) Break all (aq) into ions; not the (s) Balance and add states
NET IONIC EQUATION (NH4)2S (aq) + Cd(NO3)2 (aq) 2 NH4NO3(aq) + CdS (s) 1+ 1+ 2- 2+ 1- 1- 2 (NH4) 2 NO3 + + + 2 (NO3) + + CdS Cd 2 NH4 S (aq) (aq) (aq) (aq) (aq) (s) (aq) + Identify spectator ions and remove Write what’s left.
NET IONIC EQUATION (NH4)2S (aq) + Cd(NO3)2 (aq) 2 NH4NO3(aq) + CdS (s) 1+ 1+ 1- 1- 2 (NH4) 2 NO3 + + + 2 (NO3) + + 2 NH4 (aq) (aq) (aq) (aq) + Cd 2+ 2- CdS S (aq) (aq) (s) This is the net ionic equation.
NET IONIC EQUATION • Write the balanced equation for the reaction between sodium chloride and silver nitrate. Be sure to include states of matter • What type of reaction is it? What are the products? NaCl (aq)+ Ag(NO3) (aq) NaNO3(aq)+ AgCl (s)
NET IONIC EQUATION Na Cl NO3 Na NO3 AgCl NaCl (aq) + AgNO3 (aq) NaNO3(aq) + AgCl (s) Ag 1+ 1+ 1- 1+ 1- 1- + + + + + (s) (aq) (aq) (aq) (aq) (aq) (aq) Break all (aq) into ions; not the (s) Balance and add states
NET IONIC EQUATION NaCl (aq) + AgNO3 (aq) NaNO3(aq) + AgCl (s) 1- 1- 1+ 1+ 1- 1+ + + + + + Na Ag Na NO3 Cl NO3 AgCl (s) (aq) (aq) (aq) (aq) (aq) (aq) + Identify spectator ions and remove Write what’s left.
NET IONIC EQUATION NaCl (aq) + AgNO3 (aq) NaNO3(aq) + AgCl (s) 1- 1+ 1- 1+ + + + + + Na Na NO3 NO3 (aq) (aq) (aq) (aq) 1- 1+ AgCl + Cl Ag (s) (aq) (aq) This is the net ionic equation.
Section 4.7 Stoichiometry of Precipitation Reactions
Determining the mass of product formed • When aqueous solutions of sodium sulfate and lead (II) nitrate are mixed, lead (II) sulfate precipitates. Calculate the mass of lead (II) sulfate formed when 1.25 L of 0.0500 M lead (II) nitrate and 2.00 L of 0.0250 M sodium sulfate are mixed.
Section 4.8 Acid-Base Reactions
Brønsted-Lowry Acid & Base NH3(aq) + H2O(l) NH4+(aq) + OH-(aq) + H O N OH- H N H H H H H H H A molecule or ion that is a proton donorACID A molecule or ion that is a proton acceptorBASE
Neutralization Reactions ACID + BASE SALT + WATER • The reaction of hydronium ions and hydroxide ions to form water molecules. NaCl(aq) + HOH(l) HCl(aq) + NaOH(aq) H++Cl- + Na++OH- Na++Cl- + HOH H+ (aq)+ OH- (aq) HOH (l)
Neutralization Reactions ACID + BASE SALT + WATER • The reaction of hydronium ions and hydroxide ions to form water molecules. HC2H3O2 (aq)+ KOH(aq) KC2H3O2(aq) + HOH(l) HC2H3O2+ K++OH- K++C2H3O2-1+ HOH HC2H3O2(aq)+ OH- (aq) HOH (l)+ C2H3O2-1(aq)
Neutralization Reactions • What volume of a 0.100 M HCl solution is needed to neutralize 25.0 mL of 0.350 M NaOH? • In a certain experiment, 28.0 mL of 0.250 M HNO3 and 53.0 mL of 0.320 M KOH are mixed. Calculate the amount of water formed in the resulting reaction. What is the concentration of H+ and OH- ions in excess after the reaction goes to completion.
Acid-Base Titration • Delivery from a buret of a measured volume of a solution of known concentration (the titrant) into a solution containing the substance to be analyzed (the analyte) • Equivalence point: the point in a titration where enough titrant has been added to react exactly with the analyte • Endpoint: The point where the indicator actually changes color
Neutralization Titration/Analysis • A student weighs out a 1.3009 g sample of KHC8H4O4 . KHP has one acidic hydrogen. The student dissolves the KHP in distilled water, adds phenolpthalein and titrates the solution with sodium hydroxide to the endpoint. The difference between the final and initial buret readings indicates that 41.20 ML of the sodium hydroxide is required to react exactly with the KHP. Calculate the concentration of sodium hydroxide.
Neutralization Titration/Analysis • An environmental chemist analyzed the effluent from an industrial process known to produce the compounds CCl4 and HC7H5O2, a weak acid with one acidic hydrogen. A sample of the effluent weighing 0.3518 g was shaken with water and the resulting aqueous solution required 10.59 mL of 0.1546 M NaOH for neutralization. Calculate the mass percent of HC7H5O2 in the original sample.