Presentation on theme: "Types of Chemical Reactions And Solution Stoichiometry"— Presentation transcript:
1Types of Chemical Reactions And Solution Stoichiometry Chapter 4
2Section 4.1: Water, The Common Solvent Hydration of an ionic compound will occur when the partial positive end of a water becomes attracted to the anions in the compound; likewise for the partial negative center of the water and the cations.Solubility depends on the strength of the intermolecular attractions between the ions and water, as well as the intramolecular attractions of the cations and anions of the compound.Water has polar, covalent bonds. The oxygen atom is more electronegative, making electrons more attracted to it than to the hydrogen. This will create a dipole on the molecule, with a more positive end and a more negative end.When an ionic compound dissolves in water, the ions dissociate completely, as shown in the equation.NH4NO3(s) NH4+(aq) + NO3-(aq)
3What can dissolve in H2O? WHY? Insoluble Soluble Fats Alcohols ex: bacon greaseOilsex: cooking oilNon-Polar Substancesex: turpentineSolubleAlcoholsex: C2H5OHSugarsex: C6H12O6Ionic compoundsex: NaCl, KOH, LiBrDraw the Lewis structures for alcohol, glucose, and water. Observe how the highly EN O and less EN H are present in each of these structures (hydrogen bonding).Like Dissolves Like speaks only about polarity of a molecule. Polar things are attracted to other polar molecules; non polar molecules are attracted to other non-polar molecules. It has nothing to do with shape.WHY?Because of intermolecular forces: the OH group on the sugars and alcohols is particularly attractive to a water molecule.Generally speaking: “Like Dissolves Like”
4Section 4.2: Strong and Weak Electrolytes Solute + Solvent = SolutionStrong electrolytes conduct electricityWeak electrolytes barely conduct electricityConductivity depends upon ionizationSolute is what is being dissolved (not necessarily solid).Solvent is doing the dissolving (typically more of this present).Solution is homogeneous mixture.More ions present, more conductivity because the ions are the substances capable of carrying a charge and complete the circuit.
5All of these dissociate completely in water. Weak Electrolytes Strong ElectrolytesSoluble saltsStrong acidsStrong basesAll of these dissociate completely in water.Weak ElectrolytesWeak acidsWeak basesAll of these partially dissociate in waterHCl H+ + Cl-NaOH Na+ + OH-HC2H3O H+ + C2H3O2Weak electrolytes are represented at equilibrium because the ions combine to make the molecule again. In the case of ammonia, the ionization occurs very slowly since it is not favored to occur.Non-Electrolytes are completely molecular substances in water (not even a little dissociation); Non polar substances.
6Section 4.3: Composition of Solutions Concentration is measured in molarity, molality, and many others.Concentration DOES NOT directly express the number of ions present in a solution.M= moles soluteliters solutionMgCl2 Mg Cl-1.0 M M M
7Sample ProblemsCalculate the number of moles of Cl- ions in 1.75 L of 1 x 10-3 M ZnCl2.A chemist needs 1.0 L of 0.20 M K2Cr2O7 solution. How much solid K2Cr2O7 must be weighed out to make this solution?DUH! This is chem 1 material.
8Standard Solution: a solution whose concentration is accurately known. Example: M HCl; M NaOHCreating dilutionsChemical analysis of a compoundTheoretical CalculationsWhat would you do to prepare a standard solution? In your answer, include specific pieces of glassware, techniques, or equipment you should use.ANSWERNOW
9moles before dilution = moles after dilution DilutionsDilution is the process used to make the solution less concentrated.moles before dilution = moles after dilutionBecause M =mol/L,V1(M1) = V2(M2)Lab Technique: Use a pipet to deliver the correct amount of original solution to a volumetric flask. Add some water, swirl. Fill to line, invert.
10You have a large quantity of 1. 5 M NaOH solution available You have a large quantity of 1.5 M NaOH solution available. Dilute this to 100.0mL of a 0.05 M solution. Submit your calculations and store your final product for use in our first lab.DONOW
11Section 4.4: Types of Chemical Reactions There are more than just these few types, but in this chapter we will cover…PrecipitationAcid-baseOxidation-Reduction
12Section 4.5: Precipitation Reactions Precipitation Reactions (double displacement)Forms a solid precipitate from aqueous reactants.Color of precipitate can help in identificationSolubility rules help BUNCHESMORE…
13Solubility RULESAll compounds containing alkali metal cations and the ammonium ion are soluble.All compounds containing NO3-, ClO4-, ClO3-, and C2H3O2- anions are soluble.All chlorides, bromides, and iodides are soluble except those containing Ag+, Pb2+, and Hg2+.All sulfates are soluble except those containing Hg2+, Pb2+, Sr2+, Ca2+, and Ba2+.All hydroxides are only slightly soluble, except those containing an alkali metal, Ca2+, Ba2+,and Sr2+. NaOH and KOH are the most soluble hydroxides.All compounds containing PO43-, S2-, CO32-, and SO32- are only slightly soluble except for those containing alkali metals or the ammonium ion.
14Practice Predicting Potassium nitrate and barium chloride Sodium sulfate and lead (II) nitratePotassium hydroxide and iron (III) nitrate
15ALL REACTIONS SHOULD BE WRITTEN IN NET IONIC FORM
16Section 4.7: Stoichiometry of Precipitation Reactions Stoichiometry in a precipitation reaction is performed just like stoichiometry for a molecular reaction.You need to know which ion comes from which molecular formula.
17Sample problemCalculate the mass of solid NaCl needed to add to 1.5 L of 0.1 M silver nitrate solution to precipitate all Ag+ ions in the form of AgCl.Net Ionic Eq: Ag+ + Cl- AgCl
18General Format Write the Net Ionic Equation Calculate the moles presentIdentify the Limiting Reactant*Use Mole Ratio(s)Fancy-fy your answer (put in correct units)
19Try Me!What mass of precipitate will be produced when 50.0 mL of 0.200M aluminum nitrate is added to mL of M potassium hydroxide?
20Section 4.8: Acid-Base Reactions Acids yield H+Bases yield OH -Definitions of acid and base vary.Arrhenius and Bronsted/Lowry are common theories.Acid-Base rxns are called NEUTRALIZATIONSBases are proton acceptorsAcidsare protondonors
21Strong Acid-Strong Base (HCl) (NaOH) Both dissociate completelyH+ + OH- H2ONa+ and Cl- are spectators.Weak Acid - Strong Base(HC2H3O2) (KOH)Acetic acid will not dissociateKOH will completelyHC2H3O2 + OH- H2O + C2H3O2-K+ is a spectator.
22Stoichiometry sampleWhat volume of M HCl is needed to neutralize 25 mL of 0.35 M NaOH?H+ + OH- H2O
24To complete a successful titration… The reaction between the titrant and the analyte should be known (you should know WHAT substances you have)The equivalence point should be marked accurately (you should use the right indicator)Volume of the titrant needed to reach the equivalence point should be recorded accurately (you should use a buret!)
26Titration Try Me Calc 1A 50.0 mL sample of a sodium hydroxide solution is to be standardized M of KHP (potassium hydrogen phthalate, KHC8H4O4) is used as the titrant. KHP has one acidic hydrogen mL of the KHP solution is used to titrate the sodium hydroxide solution to the endpoint. What is the resulting concentration of the analyte?
27Titration Try Me Calc 2How many milliliters of a M sodium hydroxide solution are needed to neutralize 20.0 mL of a M sulfuric acid solution?
28Norton TutorialGo to the websiteFind the tutorial on Acid/Base ionization.Complete the tutorial question form.
29Section 4.9: Redox Reactions What is it??-A reaction that occurs in conjunction with a transfer of electrons.We assign oxidation states to individual atoms in a reaction to observe the change in electrons.Oxidation statesare written withthe +/- signbefore the quantity.Ion charges arewritten with the+/- sign behindthe quantity.
30Assigning Oxidation States The Oxidation State of…Quantity of Oxid. StateExamplesAn atom in element formZeroNa(s), O2(g)A monatomic ionEqual to the charge on the ionNa+, Cl-Fluorine in a compound-1 , alwaysHF, PF3Oxygen in a compound-2, except in peroxide where it is -1H2O, CO2, H2O2Hydrogen in a compound+1, alwaysH2O, HCl, NH3
31Oxidation= an increase in the oxidation state Reduction = a decrease in the oxidation stateoxidation2Na(s) + Cl2(g) 2NaCl(s)reduction
32The metal is oxidized and the other substance is reduced. Metal AtomOxidized Substance:Loss of electronsOxidation state increasesGets SmallerCalled the Reducing AgentOther Atome-Other IonMetalIonReduced Substance:Gain of electronsOxidation state decreasesGets BiggerCalled the Oxidizing AgentThe metal is oxidized and the other substance is reduced.
33Section 4.10: Balancing Redox How To, in Acid:Write the ½ reactionsBalance the non-H and non-O atomsBalance O by adding H2O where neededBalance H by adding H+ where neededBalance charge using e-Multiply by coefficients until both e- are equal for each ½ reactionAdd the ½ reactions together (cancel stuff)