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**Properties of Solutions**

Chapter 11

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Solutions . . . the components of a mixture are uniformly intermingled (the mixture is homogeneous).

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**Solution Composition 1. Molarity (M) = 2. Mass (weight) percent =**

3. Mole fraction (A) = 4. Molality (m) =

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**Molarity Calculations**

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Mass % Calculations

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Mole Fraction

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**Molality Calculations**

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Molarity & Molality For dilute solutions, molarity (M) and molality(m) are very similar. In previous example, M = M and m = m.

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**Normality Acid-Base Equivalents = (moles) (total (+) charge)**

Redox Equivalents = (moles)(# e- transferred)

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**Normality Calculations**

.250 M H3PO4 =______N N = M(total(+) charge) N = (0.250)(3) N = N H3PO4

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**Concentration & Density Calculations**

See Example 11.2 on pages Know how to do this problem!!

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**Steps in Solution Formation**

Step 1 - Expanding the solute (endothermic) Step 2 - Expanding the solvent (endothermic) Step 3 - Allowing the solute and solvent to interact to form a solution (exothermic) Hsoln = Hstep 1 + Hstep 2 + Hstep 3

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**Three steps of a liquid solution: 1) expanding the solute,**

2) expanding the solvent, & 3) combining the expanded solute and solvent to form the solution.

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**a) Hsoln is negative and solution process is exothermic.**

b) Hsoln is positve and solution process is endothermic.

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**Processes that require large amounts of energy tend not to**

occur. Solution process are favored by an increase in entropy.

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**Structure & Solubility**

Like dissolves like. Hydrophobic --water-fearing. Fat soluble vitamins such as A, D, E, & K. Hydrophilic --water-loving. Water soluble vitamins such as B & C. Hypervitaminosis--excessive buildup of vitamins A, D, E, & K in the body.

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Henry’s Law The amount of a gas dissolved in a solution is directly proportional to the pressure of the gas above the solution. P = kC P = partial pressure of gaseous solute above the solution C = concentration of dissolved gas k = a constant

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**Solubility of several solids as a function of temperature.**

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**The solubility of various gases at different**

temperatures.

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**When an aqueous solution and pure water are in a closed**

environment, the water is transferred to the solution because of the difference in vapor pressure.

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**Psoln = solventPsolvent**

Raoult’s Law The presence of a nonvolatile solute lowers the vapor pressure of a solvent. Psoln = solventPsolvent Psoln = vapor pressure of the solution solvent = mole fraction of the solvent Psolvent = vapor pressure of the pure solvent

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**Raoult’s Law Calculations**

Sample Exercise 11.6 on page 532. Na2SO4 forms 3 ions so the number of moles of solute is multiplied by three. Psoln = waterPwater Psoln = (0.929)(23.76 torr) Psoln = 22.1 torr

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**Vapor pressure for a solution of two volatile liquids.**

a) Ideal(benzene & toluene) -- obeys Raoult’s Law, b) Positive deviation (ethanol & hexane) from Raoult’s Law, & c) Negative deviation (acetone & water). Negative deviation is due to hydrogen bonding.

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**Liquid-Liquid Solutions**

Ptotal = PA + PB = APoA + BPoB

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**Raoult’s Law Calculations**

Sample Exercise 11.7 on page 535. A= nA/(nA+nC) A= mol/(0.100 mol mol) A = C = 0.500 Ptotal = APoA + CPoC Ptotal = (0.500)(345 torr) + (0.500)(293 torr) Ptotal = 319 torr

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**Colligative Properties**

Depend only on the number, not on the identity, of the solute particles in an ideal solution. Boiling point elevation Freezing point depression Osmotic pressure

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**Phase diagrams for pure water and for an aqueous**

solution containing a nonvolatile solute -- liquid range is extended for the solution.

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**Boiling Point Elevation**

A nonvolatile solute elevates the boiling point of the solvent. The solute lowers the vapor pressure of the solution. T = Kbmsolutei Kb = molal boiling point elevation constant m = molality of the solute i = van’t Hoff factor ( # ions formed)

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**Boiling Point Calculations**

Sample Exercise 11.8 on page 537. T = Kbmsolutei msolute = T/(Kbi) msolute = (0.34 Co)/[(0.51 Cokg/mol)(1)] msolute = 0.67 mol/kg

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**Boiling Point Calculations (Continued)**

msolute = nsolute/ kgsolvent nsolute = msolute kgsolvent nsolute = (0.67 mol/kg)( kg) nsolute = 0.10 mol

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**Boiling Point Calculations (Continued)**

n = m/M M = m/n M = g/0.10 mol M = 180 g/mol

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**Freezing Point Depression**

A nonvolatile solute depresses the freezing point of the solvent. The solute interferes with crystal formation. T = Kfmsolutei Kf = molal freezing point depression constant m = molality of the solute i = van’t Hoff factor ( # ions formed)

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**Freezing Point Calculations**

Sample Exercise on page 539. T = Kfmsolutei msolute = T/(Kfi) msolute = (0.240 Co)/[(5.12 Cokg/mol)(1)] msolute = 4.69 x 10-2 mol/kg

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**Freezing Point Calculations (Continued)**

msolute = nsolute/ kgsolvent nsolute = msolute kgsolvent nsolute = (4.69 x 10-2 mol/kg)( kg) nsolute = 7.04 x mol

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**Freezing Point Calculations (Continued)**

n = m/M M = m/n M = .546 g/7.04 x 10-4 mol M = 776 g/mol

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Osmotic Pressure Osmosis: The flow of solvent into the solution through the semipermeable membrane. Osmotic Pressure: The excess hydrostatic pressure on the solution compared to the pure solvent.

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**Due to osmotic pressure,**

the solution is diluted by water transferred through the semipermeable membrane. The diluted solution travels up the thistle tube until the osmotic pressure is balanced by the gravitational pull.

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Osmosis The solute particles interfere with the passage of the solvent, so the rate of transfer is slower from the solution to the solvent than in the reverse direction.

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**a) The pure solvent travels at a greater rate into the solution than**

solvent molecules can travel in the reverse direction. b) At equilibrium, the rate of travel of solvent molecules in both directions is equal.

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**Osmotic Pressure = MRT = osmotic pressure (atm)**

M = Molarity of solution R = Latm/molK T = Kelvin temperature

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**Osmotic Pressure Calculations**

Sample Exercise on pages = MRT M = /RT M = (1.12 torr)(1 atm/760 torr)/[( Latm/molK)(298K)] M = 6.01 x 10-5 mol/L

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**Osmotic Pressure Calculations Continued**

Molar Mass = (1.00 x 10 -3g/1.00 mL)(1000 mL/1 L)(1 L/6.01 x 10-5 mol) = 1.66 x 104 g/mol protein

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Crenation & Lysis Crenation-solution in which cell is bathed is hypertonic (more concentrated)-cell shrinks. Pickle, hands after swimming in ocean. Meat is salted to kill bacteria and fruits are placed in sugar solution. Lysis-solution in which cell is bathed is hypotonic (less concentrated)-cell expands. Intravenous solution that is hypotonic to the body instead of isotonic.

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**If the external pressure is larger than the osmotic pressure, reverse osmosis occurs.**

One application is desalination of seawater.

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**Colligative Properties of Electrolyte Solutions**

van’t Hoff factor, “i”, relates to the number of ions per formula unit. NaCl = 2, K2SO4 = 3 T = mKi = MRTi

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**Electrolyte Solutions**

The value of i is never quite what is expected due to ion-pairing. Some ions stay linked together--this phenomenon is most noticeable in concentrated solutions.

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**Osmotic Pressure Calculation for Electrolyte**

Sample Exercise on page 548. Fe(NH4)2(SO4)2 produces 5 ions. = MRTi i= /MRT i = 10.8 atm/[(0.10 mol/L)( Latm/molK)(298 K)] i = 4.4

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**aerosols, foams, emulsions, sols**

Colloids Colloidal Dispersion (colloid): A suspension of tiny particles in some medium. aerosols, foams, emulsions, sols Coagulation: The addition of an electrolyte, causing destruction of a colloid. Examples are electrostatic precipitators and river deltas.

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**The eight types of colloids and examples of each.**

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Tyndall Effect The scattering of light by particles of a colloid is called the Tyndall Effect. Which of the glasses below contains a colloid?

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Calorimeter Problem Add this problem to the Chapter 11 set of problems. KNOW how to work this problem--show the appropriate formula!! When 8.50 g of sodium nitrate is dissolved in g of water, the temperature of the solution rises Co. What is the molar heat of solution for sodium nitrate?

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Copyright©2000 by Houghton Mifflin Company. All rights reserved. 1 Chemistry FIFTH EDITION Chapter 11 Properties of Solutions

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 1 Chemistry FIFTH EDITION Chapter 11 Properties of Solutions

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