Presentation on theme: "Aqueous Reactions and Solution Stoichiometry Pg 105"— Presentation transcript:
1 Aqueous Reactions and Solution Stoichiometry Pg 105 Chapter 4Aqueous Reactions and Solution StoichiometryPg 105
2 Aqueous Solutions-Aqueous Solutions are solutions that have water as the dissolving medium.-Many reactions contain substances that have been dissolved in water, making them aqueous solutions.donkistry.tripod.com/Chem.jpg
3 3 Main Major Chemical Reaction Types Involving Aqueous Solutions Precipitation ReactionsAcid-Base ReactionsRedox Reactions
4 4.1 General Properties of Aqueous Solutions Solutions are homogeneous mixturesUsually has more solvent than solute.Solute is the substance being dissolved in the solvent
5 Electrolytic Properties Pure water is a bad conductorThe presence of Ions in water makes it into a good conductorAqueous solution that conduct electricity such as NaCl(aq) or other ionic compounds are electrolyte.Solutions that do not form ions like sucrose and other molecular compounds are nonelectrolytes.
6 Ionic Compounds in Water Ionic compounds dissolve in water dissociating into component ions (ex. NaCl -> Na+&Cl-)The polar nature of water makes it a very effective solventThe polarity helps prevent anions and cations from rejoining.
7 Molecular Compounds in Water Structure usually remains unchanged, they usually do not form ionsAcids and a few other compounds like ammonia react with water forming ions making an electrolyte.Ex. HCl make H+ and Cl- ions
8 Strong & Weak Electrolytes Strong Electrolytes = Most ionic compounds and a few molecular compounds.Weak Electrolytes = Molecular compounds that produce few ions when dissolvedIf the chemical reaction goes both ways, breaking into ions, and recombining, than the substance is a weak electrolyte.
9 HCl(aq) --> H+ + Cl- One arrow means strong electrolyte HC2H3O29(aq) <--> H+ + C2H3O2-Double arrow means weak electrolyte
10 4.2 Precipitation Reactions Precipitation Reaction = Reactions that result in the formation of an insoluble product.Precipitate = Insoluble solid formed by a reaction in a solution
11 Solubility Guidelines for Ionic Compounds Solubility = Amount of substance that can be dissolved in given amount of solventIf less than .01 mol dissolves in a liter, substance is insoluble. In these substances intermolecular attraction is stronger than the waters polarity.Table 4.1 pg 111 (Solubility Guidelines for Common Ionic Compounds in Water)All ionic compounds with 1A elements or ammonia ions are soluble in water.
12 Is Sodium Carbonate Soluble (Na2CO3) Yes. Carbonate is usually insoluble, but when paired with a 1A element, Sodium, the compound becomes soluble.
13 Exchange (Metathesis) Reactions Exchange or Metathesis Reaction = AX+BY --> AY+BXPrecipitation and Acid Base Reactions conform to this pattern
14 What precipitate forms when BaCl2 and K2SO4 are mixed? BaSO4, SO42- is soluble but Ba2+ is not
15 Ionic EquationsMolecular Equation = complete chemical formulas of reactants and productsComplete Ionic Equation = All Soluble strong Electrolytes are shown as ionsSpectator ions = ions that are present in the same form on both product and reactant side. These are dropped out to form a Net Ionic Equation.
16 Steps to Write a Net Ionic Equation Write a balanced Molecular EquationRewrite to show ions that are formed during dissociation or ionization, only the strong electrolytes are written in ionic formCancel spectator ions on both sides
17 Write the net ionic equation for the mixing of CaCl2 and Na2CO3 CaCl2(aq) + Na2CO3(aq) --> CaCO3(S) + 2NaCl(aq)Ca2++ 2Cl- + 2Na+ + CO32--->CaCO3(s) + 2Na+ + 2Cl-Ca2+(aq) + CO32-(aq)-->CaCO3(s)
18 Acid-Base Reactions Acids and Bases are common Electrolytes Are some of the most common compounds we encounter
19 AcidsSubstances that ionize in aqueous solutions upping H+ concentrationProtic refers to amount of H+ ions ionizing. Monoprotic = 1, Diprotic = 2.Diprotic Acid ionization occurs in two steps, One hydrogen is separated at a time.
20 Bases Substances that accept H+ ions, or increases OH- concentration. Does not need to have an OH- ion, if accepts H+ like NH3 (ammonia is a weak electrolyte)
21 Strong and Weak Acids and Bases Strong Acids and Bases are strong electrolytes that completely ionize in solutionsWeak Acids and Bases are electrolytes that partly ionize in solutionsTable 4.2 pg 115 (Common Strong Acids and Bases)
22 Identifying Strong and Weak Electrolytes Is the compound ionic, yes -> probably strong electrolyteNot ionic, is it an acidYes, is an acid, if strong, is a strong electrolyte if weak, is a weak electrolyte.Not an acid, is it NH3 or another molecular base, yes -> weak base, no -> probably nonelectrolyte
23 Classify HNO3 as a strong, weak, or non Electrolyte HNO3 is a strong acid making it a strong electrolyte.mls.jpl.nasa.gov/images/HNO3.jpg
24 Neutralization Reactions and Salts When acid and base react together, it is a neutralization reaction.These reactions form a salt and a water.Salt = any ionic compound whose cation comes form a base and anion comes from an acid.
25 Write the net ionic equation for HC2H3O2 and Ba(OH)2 HC2H3O2(aq)+OH-(aq)--> H2O(l) + C2H3O2-(aq)
26 Acid-Base Reaction with Gas Formation The sulfide ion and carbonate ion react with acids to form gases2HCl(aq) + Na2S(aq) --> H2S(g)+2NaCl(aq)HCl(aq)+NaHCO3(aq)-->NaCl(aq) + H2O(l)+CO2(g)
28 Oxidation and Reduction Metals undergoing erosion are losing electrons and forming cationsLoss of electrons is known as oxidizationThe gain of electrons by a substance is called reduction
29 Oxidation NumbersOxidization number is the actual charge of the of the atom.In elemental form the Oxidization number is 0Oxidization of monatomic ions equals the chargeNonmetals are usually negative, Oxygen usually is -2, Hydrogen is +1, Fluorine is -1.Sum of oxidation numbers in neutral compound is 0 or equal to the charge in a polyatomic ion.
30 Determine the oxidation stat of sulfur in H2S -2, Hydrogen is always +1 2H = +2 so S = -2 so that sum of oxidation numbers = 0
31 Oxidation of Metals by Acids and Salts Displacement Reactions = ion is solution is displaced or replaced through the oxidation of an element.A+BX-->AX+B
32 Write the net ionic equation for the reaction of aluminum and hydrobromic acid 2Al(S) + 6H+(aq)+6Br--->2Al3+(aq)+6Br-(aq)+3H2(g)2Al(s)+6H+(aq)-->2Al3++3H2(g)
33 The Activity SeriesTable 4.5 pg 124 Activity Series of Metals in Aqueous SolutionIs a table of metals arranged in order of decreasing ease of oxidation.Alkali and Alkaline Earth Metals are at the top.Metals on the list can be oxidized by any of the ions below them.
34 Can Pb(NO3)2 can oxidize Zn, Cu, or Fe Zn and FeRefer to table 4.5
35 4.5 Concentrations Of Solutions Concentration = Amount of solute dissolved in a given quantity of solvent or solution.
36 MolarityMolarity (M) = (moles of solute)/(Volume of Solution in Liters)
37 Calculate the molarity of a solution made by dissolving 23 Calculate the molarity of a solution made by dissolving 23.4 g of sodium sulfate in enough water to form 125ml of solution23.4g*(1mol Na2SO4/142g Na2SO4) = .165 mols125ml*(1L/1000ml)=.125.165mols Na2SO4/.125L = 1.32M
38 Dilution Adding water to lower the concentration is called dilution Mi*Vi=Mf*Vfi = initial f = final M = Molarity V= Volume
39 How many mL of 3.0 M H2SO4 are required to make 450 mL of .10 M H2SO4 ? Vi = (MfVf)/Mi((.10M)(450mL))/3.0M = 15 mL
41 TitrationsSecond solution of known concentration is called the standard solutionCombining the standard solution with a solution of unknown concentration to get a chemical reaction is called titrationEquivalence point is where equivalent quantities have been brought together indicators change the color helping us to find this point.If molar ratio is 1 to 1 you may use the dilution equation.If not, convert standard solution to mols, then use molar ratio to give you the mols of the unknown, then convert to grams.
42 How many grams of chloride ion are in the sample of the water if 20 How many grams of chloride ion are in the sample of the water if 20.2 mL of .1 M Ag is required to react with all the chloride in the sample?(20.2 mL solution) * (1L/1000mL solution) * (.1mol Ag+/L solution) = 2.02 * 10-31mol Ag+ : 1mol Cl-(2.02*10-3 mol Cl-) * (35.5g Cl-/1 mol Cl-) = 7.17 * 10-2 g Cl-