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Chem 162-2011 Lecture 3 part I

Chem 162-2011 Lecture 3 part I - CHEMISTRY 162-2011 Lecture...

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CHEMISTRY 162-2011 Lecture 3: 12.8-12.10; 13.1-13.3 ANNOUNCEMENTS E-MAIL ATTENDANCE Sign in QUIZ Recitation quiz this week  Chapter 12.1 – 13.3 MISCELLANEOUS Chem 162-2011 Lecture 3 1
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PLAN FOR TODAY : DO LECTURE 2 LECTURE 3 PHYSICAL PROPERTIES OF SOLUTIONS Solutions of electrolytes Colloids CHEMICAL KINETICS Chemical Kinetics – A Preview The meaning of reaction rate Measuring reaction rates Chem 162-2011 Lecture 3 2
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LECTURE 2 (CHAPTER 12.4-12.8) Chem 162-2011 Lecture 3 3
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FORMULAS g solute + g solvent = g solution mL solute + mL solvent ≠ mL solution Mass percent = grams of solute/100 g solution Mole percent = moles of solute/100 moles solution Molarity = moles of solute/L of solution ET: Molarity is temperature dependent, but molality is not. Difficult but important interconversion Molality = moles of solute/kilogram of solvent PPM = grams of solute/1,000,000 grams solution Volume percent = volume of solute/100 mL of solution Proof = 2 x Vol. %; e.g., 2 x 40 mL/100 mL solution = 80 proof Mole fraction: X A = n A /(n A + n B ) X A + X B = 1 Particle fraction: P X A = in A /(in A + in B ) P X A + P X B = 1 Raoult’s law: Don’t use: P soln = X solvent P o solvent Use: P soln = P X solvent P o solvent For two volatile components: P soln = P X solventA P o solventA + P X solventB P o solventB P X solvent = in solvent /(in solvent + in solute ) P X A + P X B = 1 van’t Hoff factor, “i”; i = moles of particles in solution/moles of solute dissolved Boiling-point elevation: ΔT = T f - T i = K b im solute Freezing-point depression: ΔT = T f - T i = -K f im solute Osmotic pressure: πV = inRT* * Begin problem with this formula, not the equivalent π = iM solute RT ΔH soln = ΔH solute-solutebondbreaking + ΔH solvent-solventbondbreaking + ΔH solute-solventbondforming Henry’s Law: S A =kP A ; M A = Solubility of dissolved gas in solution “S” may be any unit of concentration (depending on the units of “k”), e.g., X, M, %. ET note: Not everything goes through moles, e.g., volume to grams, grams to volume, atoms to molecules, molecules to atoms. Chem 162-2011 Lecture 3 4
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GAS SOLUBILITY VS. TEMPERATURE ET: Warm water kills fish due to less oxygen available. ∆G = ∆H - T∆S ∆S is negative for a gas going to a solution. Hence, “- T∆S” is a positive value for dissolving a gas, which is thermodynamically unfavorable. The larger the T, the less favorable. Chem 162-2011 Lecture 3 5
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GAS SOLUBILITY VS. PRESSURE ET: The concentration of the substance in the gas phase to the concentration of the substance in the liquid phase is a constant (an equilibrium constant), which means that if you increase the pressure of a substance in the gas phase then the concentration of that substance will increase in the liquid phase, and correspondingly, if you increase the concentration of the substance in the liquid phase then the concentration (i.e., the pressure) will increase in the gas phase; identical to Raoult’s law except that in Raoult’s law the substance in its standard state is a liquid, whereas in Henry’s law the substance in its standard state is a gas.
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