Solutions Lecture Kotz

Solutions Lecture Kotz - 1 Chapter 14 Physical Properties...

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Unformatted text preview: 1 Chapter 14 Physical Properties of Solutions alloy Concentration Units Concentration Units Concentration Units Concentration Units Molarity (M) Molarity (M) Molarity (M) Molarity (M) = moles solute / Liters of solution Percent by Mass (weight) Percent by Mass (weight) Percent by Mass (weight) Percent by Mass (weight) Percent by Volume Percent by Volume Percent by Volume Percent by Volume Parts per Parts per Parts per Parts per million - (for dilute aqueous solutions 1ppm 1mg/L, since the density is close to that of water at 1.00g/mL) Parts per billion - (1ppb 1 g/L) Parts per trillion - (1ppt 1ng/L) These units can be in terms of numbers of particles or mass (usually mass for liquids, particles for gases) Example: 1. Show that for dilute solutions, 1ppm is approximately equal to 1mg/L Example: 1. Show that for dilute solutions, 1ppm is approximately equal to 1mg/L Result: At 1.00g/mL for water there are 1,000g/L In one milligram there is .001g .001g / 1,000g = 1x10-6 = 1 / 1,000,000 = 1ppm Example: 2. What is the mass percent sucrose (table sugar) in the solution obtained by mixing 225g of an aqueous solution that is 6.25% sucrose by mass with 135g of an aqueous solution that is 8.20% sucrose by mass? 2 Example: 2. What is the mass percent sucrose (table sugar) in the solution obtained by mixing 225g of an aqueous solution that is 6.25% sucrose by mass with 135g of an aqueous solution that is 8.20% sucrose by mass? Result: (225g)(.0625) + (135g)(.0820) (225g + 135g) = .0698 = 6.98% 6.98% 6.98% 6.98% Example: 3. a. Assume that the volumes are additive, and determine the volume percent toluene C 6 H 5 CH 3 , in a solution made by mixing 40.0mL of toluene with 75.0mL of benzene, C 6 H 6 b. At 20 o C, the density of benzene is 0.879g/mL and that of toluene is 0.866g/mL. For the solution described in 3a, what is the mass percentage of toluene and the resulting solution density? Example: 3. a. Assume that the volumes are additive, and determine the volume percent toluene C 6 H 5 CH 3 , in a solution made by mixing 40.0mL of toluene with 75.0mL of benzene, C 6 H 6 b. At 20 o C, the density of benzene is 0.879g/mL and that of toluene is 0.866g/mL. For the solution described in 3a, what is the mass percentage of toluene and the resulting solution density? Result: a. 40.0mL / (40.0mL + 75.0mL) = .3478 = 34.8% 34.8% 34.8% 34.8% b. Mass% = (40.0mL)(0.866g/mL) / [(40.0mL)(0.866g/mL) + (75.0mL)(0.879g/mL)] = .344 = 34.4% 34.4% 34.4% 34.4% Density = [(40.0mL)(0.866g/mL) + (75.0mL)(0.879g/mL)] / (40.0mL + 75.0mL) = .874g/mL .874g/mL .874g/mL .874g/mL Molality (m) Molality (m) Molality (m) Molality (m) = amount of solute (mol)/mass of solvent (kg) Note that this is kilograms of solvent NOT solution....
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Solutions Lecture Kotz - 1 Chapter 14 Physical Properties...

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