Aqueous Reactions and Solution Stoichiometry

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Aqueous Reactions and Solution Stoichiometry. Chapter 4 BLB 12 th. 4.1 General Properties of Aqueous Solutions. Solution – homogeneous mixture ( ch. 13) Solvent – dissolving medium; aq-water Solute – dissolved substance Electrolytic Properties - PowerPoint PPT Presentation

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Aqueous Reactions and Solution StoichiometryChapter 4 BLB 12th14.1 General Properties of Aqueous SolutionsSolution homogeneous mixture (ch. 13)Solvent dissolving medium; aq-waterSolute dissolved substance

Electrolytic PropertiesElectrolyte a substance whose aqueous solution contains ions; conducts electricityNonelectrolyte substance that does not form ions in solutionAqueous Solutions, cont.Ionic Compounds in Water

Ionic solids dissociate (or ionize) into ions as they dissolve.hydration process of dissolving an ionic substance in watersolvation dissolving in any solvent; dissolution

Why? Water is polar.Polarity of moleculesElectrons are shared unequally.Results in partial charges (), and aDipole moment

Hydration of NaCl(s)

How many ions does an ionic compound produce when it dissociates?KCl,

MgCl2, or

K2SO4?Aqueous Solutions, cont.Molecular Compounds in Water

nonelectrolytes contain only molecules (no ions); do not dissociate; do not conduct electricity; may dissolve in waterMost molecular compounds are nonelectrolytes.Some may have strong interaction with water (alcohols).Some may dissociate (acids).

Methanol (CH3OH) in water

Aqueous Solutions, cont.Strong and weak electrolytes depend on the extent of dissociationStrong completely dissociate into ions- all water-soluble ionic compounds, strong acids & basesWeak remain mostly as neutral molecules and produce very few ions; establish chemical equilibrium- weak acids (like acetic acid) and weak bases (like amines); waterNote: strong doesnt mean soluble and vv.4.2 Precipitation ReactionsMarked by the formation of an insoluble product (precipitate)Solubility amount of solute that can be dissolved in a given amount of solvent at a certain temperature; g/100g or g/L or mol/LInsoluble solubility < 0.01 mol/LSolubility Rules Table 4.1, p. 121Metathesis (or exchange) reactionsNote: All common compounds of Group I metals and NH4+ are soluble in water.

Metathesis (or exchange) reactionsMolecular:BaCl2(aq) + Na2SO4(aq) 2 NaCl(aq) + BaSO4(s)

Complete ionic:

Net ionic:Metathesis (or exchange) reactionsMolecular:NaI(aq) + Pb(NO3)2(aq)

Complete ionic:

Net ionic:Metathesis (or exchange) reactionsMolecular:NaOH(aq) + Co(NO3)2(aq)

Complete ionic:

Net ionic:4.3 Acids, Bases, and Neutralization ReactionsInvolve H+Acid H+ donorBase H+ acceptorNeutralization:acid + base salt + waterHCl + NaOH NaCl + H2O

4.3 Acids, Bases, and Neutralization ReactionsStrong and Weak

Strong completely dissociateWeak only partially ionizeNeutralization:acid + base salt + waterHCl + NaOH NaCl + H2O

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4.4 Oxidation-Reduction (Redox) ReactionsInvolve transfer of eOxidation loss of eReduction gain of eOxidation number a charge assigned to an atom to keep track of electrons transferred during redoxDisplacement reaction ion in solution is replaced through oxidation of an element.

4.5 Concentrations of SolutionsMolarity (M) mole solute/L solutionM V = molDilution adding solvent to decrease concentrationM1V1 = M2V2mol1 = mol2; only volume changesCalculate the concentration (in M) if 2.50 g (NH4)2SO4 is dissolved in enough water to form 250 mL of solution.How many grams of K2Cr2O7 are needed to make 50.0 mL of 0.850 M solution?Ion Concentration: 0.850 M K2Cr2O7Concentration (M) of Cr2O72-?

Concentration (M) of K+?What volume (in mL) of 6.0 M HNO3 is needed to make 250 mL of 1.0 M HNO3?4.6 Solution Stoichiometry and Chemical AnalysisUse M and volume to obtain molesTitration process used to determine the concentration of a solution (p. 145 ff)Standard solution one of precisely known concentrationAnalyte solution of unknown concentrationStoichiometry Overview, p. 144