PRACTICE PROBLEMS CHEM 162-2007 EXAM I CHAPTER 12 - PROPERTIES OF SOLUTIONS SOLUTION CONCENTRATIONS CONCEPTS (Molarity, mole fraction, etc.) SOLUTION CONCENTRATIONS CALCULATIONS (Molarity, mole fraction, etc.) ENERGETICS OF SOLUTIONS AND SOLUBILITY CONCEPTS ENERGETICS OF SOLUTIONS AND SOLUBILITY CALCULATIONS VAPOR PRESSURE OF SOLUTIONS CONCEPTS (Henrys Law, Raoults Law) VAPOR PRESSURE OF SOLUTIONS CALCULATIONS COLLIGATIVE PROPERTIES (BOILING POINT, FREEZING POINT, OSMOTIC PRESSURE CHANGES) CONCEPTS COLLIGATIVE PROPERTIES (BOILING POINT, FREEZING POINT, OSMOTIC PRESSURE CHANGES) CALCULATIONS MISCELLANEOUS E. Tavss, PhD 1 FORMULAS Mass percent = grams of solute/100 g solution Molarity = moles of solute/L of solution 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: i X A = in A /(in A + in B ) i X A + i X B = 1 Raoults law: P soln = i X solvent P o solvent i X solvent = in solvent /(in solvent + in solute ) i X A + i X B = 1 P Total = P A + P B = i X A P o A + i X B P o B vant Hoff factor, i; i = moles of particles in solution/moles of solute dissolved Boiling-point elevation: T = T f- T i = K b im solute Freezing-point depression: T = T f- T i = -K f im solute (+K f gives absolute change in temp; -K f gives actual T f or T i ) Osmotic pressure: V = inRT = (n/V)iRT = iM solute RT H soln = H solute-solutebondbreaking + H solvent-solventbondbreaking + H solute-solventbondforming H hydr = H solvent-solventbondbreaking + H solute-solventbondforming H soln = H solute-solutebondbreaking + H hydr Henrys Law: X A =kP A ; X A = mole fraction of dissolved gas in solution 2 SOLUTION CONCENTRATIONS CONCEPTS CHEM 162SG-2001 HOURLY EXAM I CHAPTER 11 - PROPERTIES OF SOLUTIONS SOLUTION CONCENTRATIONS CONCEPTS 14. To 1000 g of water containing 0.010 mole of NaCl, 10.0 g of ethyl alcohol, C 2 H 5 OH(l) are added. Which quantity remains the same? A. the molarity of NaCl B. the mass percentage of NaCl C. the mole fraction of NaCl D . the molality of NaCl E. the vapor pressure of water CHEM 162-2003 HOURLY EXAM 1 + ANSWERS CHAPTER 11 - PROPERTIES OF SOLUTIONS SOLUTION CONCENTRATION CONCEPTS 1. For which of the following conversions must you know the density of the solution? A. mass percent to molality (g solute/100 g solution) x (mol/g) x 1000 g/kg = molality B . mass percent to molarity (g solute/100 g solution) x (mol/g) x (g/mL) x (1000 mL/L) = molarity C. mole fraction to mass percent ((mol A x (g/mol))/(mol A x (g/mol) + mol B x (g/mol))) x 100 = mass percent D. mole fraction to molality (mol A )/(mol A x (g/mol) + mol B x (g/mol)) x 1000 g/kg = molality E. volume percent to proof mL solute /100 mL solution x 2 = proof 1....
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