chemistry 102(01) spring 2013
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12-1CHEM 102, Spring 2013 LA TECH
Instructor: Dr. Upali Siriwardane
e-mail: upali@coes.latech.edu
Office: CTH 311
Phone 257-4941
Office Hours: M,W 8:00-9:00 & 11:00-12:00 am;
Tu,Th,F 9:30 - 11:30 am.
Test Dates:
Chemistry 102(01) Spring 2013
September 27, 2013 (Test 1): Chapter 12 & 13
April 24, 2013 (Test 2): Chapter 14 & 15
May13, 2013 (Test 3) Chapter 16 & 17
May 15, 2012 (Make-up test) comprehensive: Chapters 12-17 9:30-10:45:15 AM, CTH 328
12-2CHEM 102, Spring 2013 LA TECH
REQUIRED :
Textbook: Principles of Chemistry: A Molecular Approach, 2nd Edition-Nivaldo J. Tro - Pearson Prentice
Hall and also purchase the Mastering Chemistry
Group Homework, Slides and Exam review guides and sample exam questions are available online:
http://moodle.latech.edu/ and follow the course information links.
OPTIONAL :
Study Guide: Chemistry: A Molecular Approach, 2nd Edition-Nivaldo J. Tro 2nd Edition
Student Solutions Manual: Chemistry: A Molecular Approach, 2nd Edition-Nivaldo J. Tro 2nd
Text Book & Resources
12-3CHEM 102, Spring 2013 LA TECH
Chapter 12. Solutions 12.1 Thirsty Solutions:
12.2 Types of Solutions and Solubility
12.3 Energetics of Solution Formation
12.4 Solubility Equilibrium and Factors Affecting solution Formation
12.5 Expressing Solution Concentration
12.6 Colligative Properties: Vapor Pressure, Freezing Point, Boiling Point, Osmatic Pressure
12.7 Colligative properties of Strong Electrolytes
12-4CHEM 102, Spring 2013 LA TECH
Effect of Solutes on SolutionColligative Properties
Colligative Properties: Depend on the number of particles not on the identity of the particles
Solution Colligative Propertiesa) Vapor Pressure Loweringb) Freezing Point Depressionc) Boiling Point Elevationd) Osmotic Pressure
Two types of solutes affect colligative properties differentlya) Volatile solutes (covalent)b) nonvolatile solutes (ionic)
12-5CHEM 102, Spring 2013 LA TECH
1) What are colligative properties?
12-6CHEM 102, Spring 2013 LA TECH
Vapor Pressure ofPure Water vs. Sea Water
12-7CHEM 102, Spring 2013 LA TECH
Vapor Pressure LoweringRaoult’s Law
P1 = X1P1o
Psol = solvent Psolvent
Psol = (1-solute) Psolvent
The vapor pressure above a glucose-water solution at 25oC is 23.8 torr. What is the mole fraction of glucose (non-dissociating solute) in the solution. The vapor pressure of water at 25oC is 30.5 torr.
12-8CHEM 102, Spring 2013 LA TECH
Vapor Pressure Lowering
12-9CHEM 102, Spring 2013 LA TECH
2) What’s Rauolts Law? How it applies to a) a volatile & nondissociating,
b) nonvolatile & nondissociating,
c) nonvolatile & dissociating solutes in a solution of volatile solvent.
12-10CHEM 102, Spring 2013 LA TECH
3) What is the vapor pressure (atm) of a solution of a nonvolatile, nondissociating solute(mole fraction 0.25) in water at 50oC? The vapor pressure of water at 50oC is 0.122 atm.
12-11CHEM 102, Spring 2013 LA TECH
4) What is the total pressure at 25oC of a solution of 2.90 moles of C6H14 and 5.94 moles of C6H12 at 25oC if the vapor pressures of the pure solvents are 151 and 98 mm Hg respectively at 25oC?(Atomic weights: C = 12.01, H = 1.008, Cl = 35.45).
12-12CHEM 102, Spring 2013 LA TECH
Acetone/water(CH3)2CO/H2O
12-13CHEM 102, Spring 2013 LA TECH
Ethanol(C2H5OH)/hexane(C6H14)
12-14CHEM 102, Spring 2013 LA TECH
Benzene (C6H6)/toluene CH3C6H5
12-15CHEM 102, Spring 2013 LA TECH
Deviations from Raoult’s LawIntermolecular forces between components in a
dissolved solution cause deviations from the adjustment to vapor pressure.
Vapo
r Pre
ssur
e
A
Pvap A
Pvap B
12-16CHEM 102, Spring 2013 LA TECH
Ideal, Negative, Positive Behavior of Vapor Pressure of
Two Volatile Liquids
12-17CHEM 102, Spring 2013 LA TECH
5) What is ideal, positive and negative behavior applying Raoult's Law.
Ideal:
Positive:
Negative:
12-18CHEM 102, Spring 2013 LA TECH
Effect on Boling and Freezing point
12-19CHEM 102, Spring 2013 LA TECH
Boiling Point Elevation
12-20CHEM 102, Spring 2013 LA TECH
Boiling Point ElevationDTb = Tfinal - Tinitial
(DTb = bpsolution - bppure solvent)DTb = kb x mwhere kb => boiling point elevation constant
m => molality of all solutes in solutionFreezing Point Depression
(DTf = fppure solvent - fpsolution)
DTf = kf x m
where kf => freezing point depression constant
m => molality of all solutes in solution
For electrolytes multiply
i => number of particles per formula unit
12-21CHEM 102, Spring 2013 LA TECH
Boiling Point Elevation & Freezing point Depression Constants
12-22CHEM 102, Spring 2013 LA TECH
What is the freezing point of a 0.500 m aqueous solution of glucose? (Kf for H2O is 1.86 oC/m) (DTf = fppure solvent - fpsolution)DTf = kf x m
Freezing Point Depression Problem
12-23CHEM 102, Spring 2013 LA TECH
Calculation of Molecular Weight
A 2.25g sample of a compound is dissolved in 125 g of benzene. The freezing point of the solution is 1.02oC. What is the molecular weight of the compound? Kf for benzene = 5.12 oC/m, freezing point = 5.5oC. DTf = kf x mm = moles/ kg of solventMW = g/moles
12-24CHEM 102, Spring 2013 LA TECH
Solvent Freezing
12-25CHEM 102, Spring 2013 LA TECH
Colligative Properties ofElectrolytesNumber of solute particles in the solution depends
on dissociation into ions expressed as Van’t Hoff facotor(i)
Van’t Hoff facotor (i) moles of particles in solution moles of
solutes dissolved
12-26CHEM 102, Spring 2013 LA TECH
Colligative Properties of ElectrolytesIonic vs. covalent substances
vpwater > vp1M sucrose > vp1M NaCl > vp 1M CaCl2
1 mole sucrose = 1 mole molecules (i = 1)1 mole NaCl = 2 mole of ions (i = 2)1 mole CaCl2 = 3 moles ions (i = 3)
i => number of particles per formula unitPsol = (1- i solute) Psolvent
DTf = i kf x mDTb = i kb x mP = i MRT
12-27CHEM 102, Spring 2013 LA TECH
Osmosis
12-28CHEM 102, Spring 2013 LA TECH
Measuring Osmotic Pressure
12-29CHEM 102, Spring 2013 LA TECH
Osmosis and the Cell
12-30CHEM 102, Spring 2013 LA TECH
Osmotic Pressure
P = MRTiwhere P => osmotic pressure
M => concentration R => gas constant T => absolute Kelvin temperature
i => number of particles per formula unit
12-31CHEM 102, Spring 2013 LA TECH
Calculate the osmotic pressure in atm at 20oC of an aqueous solution containing 5.0 g of sucrose (C12H22O11), in 100.0 mL solution.M.W.(C12H22O11)= 342.34P = MRT R = 0.0821 L-atm/mol K = 62.4 L-torr/mol K
Calculation
12-32CHEM 102, Spring 2013 LA TECH
Calculate the osmotic pressure in torr of a 0.500 M solution of NaCl in water at 25oC. Assume a 100%dissociation of NaCl.
Calculation
12-33CHEM 102, Spring 2013 LA TECH
Define the Van't Hoff factor (i). Which of the following solutions will show the highest osmotic pressure: a) 0.2 M Na3PO4 b) 0.2 M C6H12O6 (glucose)c) 0.3 M Al2(SO4)3 d) 0.3 M CaCl2 e) 0.3 M NaCl
Which one has higher Osmotic Pressure
12-34CHEM 102, Spring 2013 LA TECH
6) Which of the following solutes dissolved in 1000 g of water estimate the number particles in the solution? Use Vant Hoff factor.
0.030 moles urea, CO(NH2)2 (a covalent compound) 0.030 moles acetic acid, CH3COOH(weak acid) 0.030 moles ammonium nitrate, NH4NO3(soluble) 0.030 moles calcium sulfate, CaSO4 (insoluble) 0.030 moles aluminum chloride, AlCl3 (soluble)
12-35CHEM 102, Spring 2013 LA TECH
7) Determine the molecular weight of acetic acid if a solution that contains 30.0 grams of acetic acid per kilogram of water freezes at -0.93oC. Do these results agree with the assumption that acetic acid has the formula CH3CO2H? Kf (water) = 1.86.
12-36CHEM 102, Spring 2013 LA TECH
8) Explain why a 0.100 m solution of HCl dissolved in benzene has a freezing point depression of 0.512oC, while an 0.100 m solution of HCl in water has a freezing point depression of 0.352oC. Kf (benzene) = 5.5, Kf (water) = 1.86
12-37CHEM 102, Spring 2013 LA TECH
Normal vs. Reverse Osmosis
12-38CHEM 102, Spring 2013 LA TECH
Predict the type of behavior (ideal, negative, positive) based on vapor pressure of the following pairs ofvolatile liquids and explain it in terms of intermolecular attractions: a) Acetone/water(CH3)2CO/H2Ob) Ethanol(C2H5OH)/hexane(C6H14) c) Benzene (C6H6)/toluene CH3C6H5.
Ideal, Negative, Positive Behavior of Vapor Pressure
12-39CHEM 102, Spring 2013 LA TECH
a) True solutionsb) Colloids (Tyndall effect)c) Suspensions.
Types of Solutions
12-40CHEM 102, Spring 2013 LA TECH
12-41CHEM 102, Spring 2013 LA TECH
Solution vs. Dispersion vs. SuspensionSmaller particles => Larger particles
Colloidal True solution dispersion Suspension
Particles Ions & molecules Colloids Large-sized particles
Particle size 0.2-2.0 nm 2-2000 nm >2000 nmProperties * Don’t settle out * Don’t settle out * Settle out on
on standing on standing on standing* Not filterable * Not filterable * Filterable
Example Sea water Fog River silt
12-42CHEM 102, Spring 2013 LA TECH
Tyndall Effect
12-43CHEM 102, Spring 2013 LA TECH
Surfactants
12-44CHEM 102, Spring 2013 LA TECH
Soaps and Detergents
CH 3CH 2CH2CH 2CH 2CH 2CH2CH 2CH 2CH 2CH2CH 2CH 2CH 2CH2CH 2CH 2
Hydrophobic end Hydrophilic end
sodium stearate
C O-Na+
O
CH 3CH 2CH2CH 2CH 2CH 2CH2CH 2CH 2CH 2CH2CH 2OS O-3Na +
sodium lauryl sulfate
12-45CHEM 102, Spring 2013 LA TECH
Cleaning Action
12-46CHEM 102, Spring 2013 LA TECH
Earth’s Water Supply
12-47CHEM 102, Spring 2013 LA TECH
Treatment of Drinking Water
12-48CHEM 102, Spring 2013 LA TECH
Hard Waternatural water containing relatively high
concentrations of Ca+2, Mg+2, Fe+3, or Mn+2 cations and CO3
-2 and HCO3-1 anions
12-49CHEM 102, Spring 2013 LA TECH
Common HazardousHousehold Chemicals
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