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Transcript of 1 Solution Conductivity. Guiding Questions What is meant by dissociation? What is the molecular...

  • *Solution Conductivity

  • Guiding QuestionsWhat is meant by dissociation?

    What is the molecular arrangement of water molecules?*

  • *A. DefinitionsSolution - homogeneous mixtureSolvent - present in greater amountSolute - substance being dissolved

  • *Why do some solutions conduct electricity?An early hypothesis was that electricity produced ions in solution, and those ions allowed the electricity to flow.Arrheniuss theory:Certain substances dissociate into cations and anions when dissolved in water.The ions already present in solution allow electricity to flow.Arrheniuss Theory ofElectrolytic Dissociation

  • *Dissociationhttp://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/molvie1.swf

  • Nonpolar vs. PolarWhen nonpolar substances dissolve in one another, they simply mix.When polar substances dissolve, electrical reactions pull apart the molecules.

  • IONIC COMPOUNDSCompounds in Aqueous SolutionMany reactions involve ionic compounds, especially reactions in water aqueous solutions.KMnO4 in water

  • *ELECTROLYTESAre substances that form positive(+) and negative (-) ions in waterConduct an electric current

  • *A strong electrolyte dissociates completely.A strong electrolyte is present in solution almost exclusively as ions.Strong electrolyte solutions are good conductors.A weak electrolyte dissociates partially.Weak electrolyte solutions are poor conductors.Different weak electrolytes dissociate to different extents.A nonelectrolyte does not dissociate.A nonelectrolyte is present in solution almost exclusively as molecules.Nonelectrolyte solutions do not conduct electricity.

    Types of Electrolytes

  • * Electrolytes dissociate to produce ions.Electrolytic Properties of Aqueous SolutionsThe more the electrolyte dissociates, the more ions it produces.

  • *Strong electrolytes include:Strong acids (HCl, HBr, HI, HNO3, H2SO4, HClO4)Strong bases (IA and IIA hydroxides)Most water-soluble ionic compoundsWeak electrolytes include:Weak acids and weak basesA few ionic compoundsNonelectrolytes include:Most molecular compoundsMost organic compounds (most of them are molecular)

    Is it a strong electrolyte, a weak electrolyte, or a nonelectrolyte?How do we tell whether an acid (or base) is weak?

  • *B. SolvationStrongElectrolyteNon-Electrolytesolute exists asions only

    solute exists asmolecules only

    WeakElectrolytesolute exists asions andmoleculesDISSOCIATIONIONIZATIONView animation online.

  • *Electrolytes in the BodyCarry messages to and from the brain as electrical signals

    Maintain cellular function with the correct concentrations electrolytes

    Make your own50-70 g sugarOne liter of warm waterPinch of salt200ml of sugar free fruit squashMix, cool and drink

    **To play the movies and simulations included, view the presentation in Slide Show Mode.

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