Presentation on theme: "Aqueous solutions Types of reactions"— Presentation transcript:
1 Aqueous solutions Types of reactions Chapter 4Aqueous solutionsTypes of reactions
2 solution mixture homogeneous heterogeneous solvent Solute(s) two phasesoil/watermilkone phaseTab watersolutionsolventSolute(s)more abundantcomponent of mixturewater in tab waterLess abundant or other component(s) of mixturesalts in tab waterWater always solvent even in 98% H2SO4
4 Hydration of Solid Solute At edges, fewer oppositely charged ions aroundH2O can come in; Ion-dipole forces; Remove ionNew ion at surfaceProcess continues until all ions in solutionHydration of ionsCompletely surrounded by solvent
5 Molecular Compounds In Water When molecules dissolve in waterSolute particles are surrounded by waterMolecules are not dissociatedFig 5.6
6 Electrical conductivity of electrolyte solutions Weak acids and basesEx. Acetic acid (HC2H3O2), ammonia (NH3)Ionic compoundsStrong acids and basesEx. NaBr, KNO3, HClO4, HCl, KOHEx. Sugar, alcohol
7 Learning CheckWrite the equations that illustrate the dissociation of the following salts:Na3PO4(aq) →Al2(SO4)3(aq) →CaCl2(aq) →Ca(MnO4)2(aq) →3 Na+(aq) + PO43(aq)Ca2+(aq) Cl(aq)
8 SolubilityMaximum amount of a substance that can be dissolved in a given amount of solvent at a given temperature.Usually g/100 mL.Saturated solution: Solution in which no more solute can bedissolved at a given temperatureUnsaturated solution: Solution containing less solute than max.amount; Able to dissolve more solute
9 Solubilities of Some Common Substances FormulaSolubility(g/100 g water)Sodium chlorideNaCl35.7 at 0°C39.1 at 100°CSodium hydroxideNaOH42 at 0°C347 at 100°CCalcium carbonateCaCO3at 25°C
10 “Like dissolves Like” polar ↔ polar Ethanol (C2H5OH) dissolves in water:polar ↔ polarGlucose (C6H12O6) and sucrose (C12H22O11) dissolve in water: polar ↔ polarOil doesn’t dissolve in water: nonpolar ↔ polarOil dissolves in benzene: nonpolar ↔ nonpolar
11 Water unable to separate Ag+ from Cl- Interaction very strong Salts are polar.solubleinsolubleAgClNaClWater unable to separate Ag+ from Cl-Interaction very strong
12 Relative Concentration Solute-to-solvent ratioDilute solutionSmall solute to solvent ratioEx. EyedropsConcentrated solutionLarge solute to solvent ratioEx. Pickle brineDilute solution contains less solute per unit volume than more concentrated solutionFigure 5.2Eyedrops = Low concentration of NaCl in waterPickle brine = high concentration ofNaCl in water
13 Molarity quantitatively abbreviated M 1 M = 1 mol solute / 1 liter solution
14 Preparing Solution of Known Molarity a b c d eWeigh solid and transfer to volumetric flaskAdd part of the waterDissolve solute completelyAdd water to reach etched lineStopper flask and invert to mix thoroughlyFig 5.24
15 Concentration of each type of ions in 0.50 M Co(NO3)2(aq)? 1 mol mol molIn 1.00 L mol mol molMolarity M M MConcentration of each type of ions in 0.50 M Fe(ClO4)3(aq)?Molarity M M M
16 Moles of Cl- 1.75 L of 1.0×10-3 M ZnCl2(aq)? 1.75×10-3 mol ?
18 PracticeHow many grams of HCl would be required to make mL of a 2.7 M solution?What would the concentration be if you used 27g of CaCl2 to make 500. mL of solution? What is the concentration of each ion?Describe how to make 1.00 L of a M K2CrO4 solution.Describe how to make 250. mL of an 2.0 M copper (II) sulfate dihydrate solution.Calculate the concentration of a solution made by dissolving 45.6 g of Fe2(SO4)3 to 475 mL. What is the concentration of each ion?
19 Describe how to make 1.00 L of a 0.200 M K2CrO4 solution.
20 No solid K2CrO4 available in the lab . But 2.00 M K2CrO4 solution is available .
22 Prepare 150 mL of 0.100 M H2SO4 from 16.0 M solution. What volume of a 1.7 M solution is needed to make 250 mL of a 0.50 M solution?18.5 mL of 2.3 M HCl is added to 250 mL of water. What is the concentration of the solution?You have a 4.0 M stock solution. Describe how to make 1.0 L of a 0.75 M solution.
23 Types of Chemical Reactions Reduction-OxidationMetathesisDouble ReplacementElectron transferAB + CD AD + CBprecipitation reactionAcid-Base Reactiona solid is formed from solutionprecipitateFormation of a weak electrolyteFormation of a gas
25 Net ionic equation: describes what really happens. Molecular equationIonic equationNet ionic equation: describes what really happens.Spectator ions:A reaction takes place if it has a net ionic equation
26 Solubility Rules All nitrates and acetates are soluble Salts of alkali metals ions and NH4+ ions are soluble.Chlorides, bromides and iodides (salts of Cl-, Br- and I-) are soluble except those of Ag+, Pb2+, and Hg22+.Most sulfates are soluble, except those of Pb2+, Ba2+, Hg2+, and Ca2+.Most hydroxides are slightly soluble (insoluble) except those of alkali metals (Ba(OH)2, Sr(OH)2 and Ca(OH)2 are marginally soluble).Sulfides (S2-), carbonates (CO32-), chromates (CrO42-) and phosphates (PO43-), are insoluble except those of alkali metals and NH4+.
27 Does the following mixing process involve a chemical reaction?
32 1. 25 L of 0. 0500 M Pb(NO3)2 mixed with 2. 0 L of 0. 0250 M Na2SO4 1.25 L of M Pb(NO3)2 mixed with 2.0 L of M Na2SO4. Calculate the mass of precipitate.mol ?mol ?
33 Stoichiometry of Precipitation What mass of solid is formed when mL of M Barium chloride is mixed with mL of M sodium hydroxide?What volume of M HCl is needed to precipitate the silver from 50.0 ml of M silver nitrate solution ?25 mL 0.67 M of H2SO4 is added to 35 mL of M CaCl2 . What mass CaSO4 Is formed?
34 HC2H3O2(aq) + H2O H3O+(aq) + C2H3O2−(aq) Arrhenius AcidSubstance that reacts with water to produce the hydronium ion, H3O+Acid H2O Anion + H3O+HA H2O A– + H3O+HC2H3O2(aq) + H2O H3O+(aq) + C2H3O2−(aq)HCl(g) + H2OCl–(aq) + H3O+(aq)Fig 5.10Note for organic acidsIn general, only hydrogen written first in formula transfers to H2O to give H3O+.Bronsted-Lowry Acid: H+ donor
35 Bronsted Base: H+ acceptor Arrhenius BasesSubstance that reacts with water to give OH–.Metal HydroxidesNaOH(s) Na+(aq) + OH–(aq)Mg(OH)2(s) Mg2+(aq) + 2OH–(aq)Basic AnhydridesCaO(s) + H2O Ca(OH)2(aq)Ca(OH)2(aq) Ca2+(aq) + 2OH–(aq)c. Molecular bases:NH3(aq)+H2O NH4+(aq)+ OH-(aq)Bronsted Base: H+ acceptor
37 HAc + H2O H3O+(aq)+ Ac-(aq) Formation of Weak electrolyte:HAc + H2O H3O+(aq)+ Ac-(aq)Acid - Base Reactions are often called neutralization reaction Because the acid neutralizes the base.
38 Volume of 0.100 M HCl needed to neutralize 25.0 mL of 0.350 M NaOH ? ? ×10-3
39 28.0 mL of 0.250 M HNO3 mixed with 53.0 mL of 0.320 M KOH; Amount of water formedConcentrations of H+ and OH- at the end of rct7.0 mmol ?17.0 mmol ?
40 HNO3 is Limiting reactant: reacts completely No HNO3 left HNO3 → H+ + NO3-No H+ at the end of reactionHow much remains from KOH?KOH → K+ + OH-10 → mmol
41 Volumetric analysis: Titration Controlled addition of 1 reactant to another until rxn is complete.Acid-Base Titration: Very common type of titrationEx. Analysis of citric acid in orange juice by neutralization with NaOH
42 Acid (Base) added equivalent to base (acid) present An indicator is needed: organic substance that changes color according to solution acidityWhere the indicator changes color is the endpoint.Endpoint must be very close to the equivalence point.Acid (Base) added equivalent to base (acid) presentPhenolphthaleinAcidic Basic
43 Standardization of NaOH solution Know the exact concentration!Its weight is inaccurate .NaOH is hygroscopic and it absorbs CO2.Cannot be used to prepare solutions with exactly known M.Not a primary standard.KHP is a primary standard: high purity, no weighing problems,Potassium hydrogen phthalate: KHC8H4O4.Monoprotic!41.2 mL of NaOH solution is needed to react exactly with g of KHP (M= g/mol).MNaOH=?
46 practice75 mL of 0.25M HCl is mixed with 225 mL of M Ba(OH)2 . What is the concentration of the excess H+ or OH- ?A mL sample of aqueous Ca(OH)2 requires mL of M Nitric acid for neutralization. What is [Ca(OH)2 ]?