151F09_W13_LV_4_short - UA GenChem General Chemistry...

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Unformatted text preview: UA GenChem General Chemistry General Chemistry CHEM 151 CHEM 151 Week 13 UA GenChem Exam 3 Monday Nov. 16th Electron dots we can see will be counted! Include ALL electrons in a Lewis structure ! Dont forget individual brackets and arrows in resonance structures Remember brackets with outside charges for charged molecules Properties and types of substances will be on this exam (i.e. does not conduct electricity as a solid but does when dissolved = ionic compound.) Bring your calculator! UA GenChem SOLUBILITY: IONIC COMPOUNDS Some ionic compounds are very soluble in water, while others are almost completely insoluble. Water and ions must interact to cause solubility. UA GenChem Ion-Ion Interactions Why does water align this way? UA GenChem Attraction between ions and dipole depends on ion charge and ion-dipole distance 1922 kJ/mol 1922 kJ/mol 405 kJ/mol 405 kJ/mol 263 kJ/mol 263 kJ/mol O H H + - O H H + - O H H + - Na + Mg 2+ Cs + Solubility: Ionic Compounds Ionic compounds with large ions have weaker ion-ion interactions. The interactions with water are also weaker . So, sometimes ionic substances with large ions are insoluble . UA GenChem Aqueous Solutions To explain, predict, and control chemical reactions in water we need to understand what happens when molecular and ionic compounds dissolve in water. For example, when some substances dissolve in water they generate solutions that can conduct electricity. Why? UA GenChem Some dissolved materials conduct electricity well, others conduct poorly. Strong Electrolyte Weak Electrolyte Aqueous Solutions UA GenChem Some dissolved materials conduct electricity well, others poorly, and some not at all. Non Electrolyte Aqueous Solutions UA GenChem Electrolytes: contain ? and conduct electricity Aqueous Solutions UA GenChem Electrolytes: contain free ions and conduct electricity Aqueous Solutions UA GenChem This concentration is commonly expressed in g/L or mol/L ( Molarity ) Molarity = moles of solute/liters of solution = n/V Solubility A measure of the amount of a substance that will dissolve in a solvent (saturated) The concentration of the solution represents the relative amounts of solute and solvent in the system It is temperature dependent All about intermolecular forces, ie. Solubility increases if solvent-solute forces are equal to or greater than solute-solute and solvent-solvent forces UA GenChem Solubility The solubility of NaCl in water is 359 g/L at 25 o C. What is the Molar concentration solution of this compound? 359 g 1 L 1 mol NaCl 58.44 g NaCl = 6.14 mol/L = 6.14 M X UA GenChem Which solution could this be?...
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This note was uploaded on 02/06/2012 for the course CHEM 151 taught by Professor Staff during the Fall '08 term at University of Arizona- Tucson.

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151F09_W13_LV_4_short - UA GenChem General Chemistry...

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