110_Fa11_LUZ-week10ST (1)

110_Fa11_LUZ-week10ST (1) - Week 10: Lectures 28 30...

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Jensen Chem 110 Chap 13 Page: 1 Week 10: Lectures 28 – 30 Lecture 28: W 10/26 Lecture 29: F 10/28 Lecture 30: M 10/31 (Halloween Demo Show) Reading: BLB Ch 4.1, 4.5, 13.1 – 13.4 Homework: BLB 4: 3, 37, 72; Supp 4: 1 – 5; BLB 13: 7, 21, 23; Supp 13: 1 - 12 Reminder: Angel Quiz 9 due on Thur 10/27 ALEKS Objective 10 due on Tue 11/1 Jensen Office Hour: 501 Chemistry Building Tuesdays & Thursdays, 10:30 – 11:30 am Exam 3: Mon, Nov. 7, 6:30 – 7:45 pm Jensen Chem 110 Chap 13 Page: 2 Solutions Solutions: Homogeneous mixtures of 2 or more substances; uniformly mixed on a molecular level Solute: what dissolves ( a change in state [or phase] ); typically the minor component Solvent: what the solute is dissolved in ( unchanged state ); the major component Aqueous Solution: solvent is water Critical aspects with regard to solutions how does the solute exist in the solution free ions? = electrolyte (weak or strong) no ions? = nonelectrolyte what goes into the solution concentration solubility (BLB Table 4.1)
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Jensen Chem 110 Chap 13 Page: 3 Solute: what type of compound? Ionic compounds: compounds consisting of positive and negative ions Metal + nonmetal (usually) e.g. NaCl Mg(NO 3 ) 2 Na 2 SO 4 NH 4 Cl Molecular compounds: compounds consisting of individual molecules All nonmetals or nonmetals and metalloids e.g. H 2 O HCl CH 3 COOH NH 3 Jensen Chem 110 Chap 13 Page: 4 The Solution Process Solutions form when the solute – solvent IM forces are comparable in magnitude and nature to the combined solute – solute and solvent – solvent IM forces 1. Break solute – solute interactions ( ! H 1 ) 2. Break solvent – solvent interactions ( ! H 2 ) " Energy is ____________ 3. Form solute – solvent interactions ( ! H 3 ) " Energy is ____________ Processes occur spontaneously when: ! energy is released (exothermic) ! disorder increases
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Chem 110 Chap 13 Page: 5 Enthalpy Changes for the Solution Process The enthalpy change of the overall process depends on ! H for each of these steps Left: Net exothermic process ( ! H soln <0 ) Example: NaCl Right: Net endothermic process ( ! H soln >0 ) Example: NH 4 NO 3 A process can be endothermic and spontaneous when the increase in disorder is large enough. Jensen Chem 110 Chap 13 Page: 6 Dissolution of NaCl in water Ion-dipole attractions between the ions and water molecules are sufficiently strong to pull the ions from their positions in the crystal. NaCl(s) + H
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This note was uploaded on 01/18/2012 for the course CHEM 110 taught by Professor Hofmann,brucerob during the Fall '08 term at Penn State.

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110_Fa11_LUZ-week10ST (1) - Week 10: Lectures 28 30...

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