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UB CHE 102 - Osmotic Pressure and Chemical Kinetics

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Chem 102 1st Edition Lecture 2 Outline of Last Lecture- Chapter 13 part 2 & Chapter 14I. The Solution ProcessA. Energy Changes and Solution FormationII. Expressing Concentration (formulas)III. Solution: Saturation and SolubilityIV. Henry’s LawV. Colligative PropertiesA. Freezing Point DepressionB. Raoult’s Law, VaporC. Boiling Point ElevationOutline of Current Lecture I. Colligative Properties cntd.A. Osmotic PressureII. Chemical KineticsA. Thermodynamics vs. KineticsB. Reaction RatesC. Rate LawCurrent LectureI. Colligative Properties Continued- Recall from lecture 1 these are the properties that depend on quantity of solute molecules or ions not their identities. These include freezing point, vapor pressure, boiling point, and osmotic pressure.A. Osmotic Pressure-Osmosis is the movement of solvent from low soluteconcentration to high solute concentration. As a solvent moves across the membrane fluid levels in the arms become uneven, this is osmotic pressure, the pressure that stopsosmosis. Eventually this unevenness in pressure stops osmosis.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.-Semipermeable Membrane- a membrane that permits the passage of some solution such as a cell membrane or cellophane. There is movement in both directions across a semipermeable membraneOsmotic Pressure: -Isotonic Solution- 2 solutions with the same p separated by a semipermeable membrane.-Hypotonic Solution- A solution of a lower p than in a hypertonic solution-Osmosis is spontaneous -Red Blood Cells are surrounded by a semipermeable membrane-Crenation-Red blood cells are placed in a hypertonic solution, there is a lower solute concentration in the cell than the surrounding tissue. Osmosis occurs and water passes through the membrane causing the cell to shrivel up. Example: Cucumber being placed in NaCl(salt) the cucumber will shrivel up and become apickle -Hemosis-On the other hand, red blood cells are placed in a hypotonic solution, the solute concentration is higher then in the cell.Osmosis occurs and water moves into the cell causing the cell to burst. -To prevent Hemosis or Crenation, intravenous (IV) solutions must be isotonic(a)- Crenation (b)-HemosisII. Chemical Kinetics- The 2 energy related factors that determine the chemical reactionA. Thermodynamics vs. Kinetics-Thermodynamics- Reaction occurs only if the products aremore stable than the reactants.-Kinetics- Reaction only occurs if there is a low energy pathway to proceed from reactants to products at a reasonable time, the study of how fast chemical reactions occur. B. Reaction Rates (kinetics)-How fast a reaction rate occurs. Two ways of measure this. 1. Speed at which products appear and 2. Speed at which reactants disappear. As products appear, reactants will be disappearing.- 4 major factors that affect the rate of reaction:1. Reactant concentration2. Temperature3. Action of catalysts4. Surface areaAverage Rate=Δ(moles B)/Δt C. Rate Law-**********************ON TESTRate = k[reactant 1]m[reactant 2]n -We say the reaction is mth order in reactant 1 and nth order in reactant 2.-The overall order of reaction is m + n + …. -A reaction can be zeroth order if m, n, … are zero. -The values of the exponents (orders) have to be determined experimentally. They are not simply related to stoichiometry. -A reaction is zero order in a reactant if the change in concentration of that reactant produces no effect. -A reaction is first order if doubling the concentration causes the rate to double. -A reaction is second order if doubling the concentration results in a 22 increase in rate. -A reaction is nth order if doubling the concentration causes an 2n increase in rate.*the rate constant does not depend on concentration* - In general, for the rate expression:rate = k [A]n[B]m -In two experiments where [B] is constantrate1 = k [A1]n[B]m and rate2 = k


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