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CHEM 120: Introduction to Inorganic Chemistry. Instructor: Upali Siriwardane (Ph.D., Ohio State University) CTH 311, Tele: 257-4941, e-mail: upali@chem.latech.edu Office hours: 10:00 to 12:00 Tu & Th ; 8:00-9:00 and 11:00-12:00 M,W,& F. Chapters Covered and Test dates.
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CHEM 120: Introduction to Inorganic Chemistry Instructor: Upali Siriwardane (Ph.D., Ohio State University) CTH 311, Tele: 257-4941, e-mail: upali@chem.latech.edu Office hours: 10:00 to 12:00 Tu & Th ; 8:00-9:00 and 11:00-12:00 M,W,& F
Chapters Covered and Test dates • Tests will be given in regular class periods from 9:30-10:45 a.m. on the following days: September 22, 2004 (Test 1): Chapters 1 & 2 • October 8, 2004(Test 2): Chapters 3, & 4 • October 20, 2004 (Test 3): Chapter 5 & 6 • November 3, 2004 (Test 4): Chapter 7 & 8 • November 15, 2004 (Test 5): Chapter 9 & 10 • November 17, 2004 MAKE-UP: Comprehensive test (Covers all chapters • Grading: • [( Test 1 + Test 2 + Test3 + Test4 + Test5)] x.70 + [ Homework + quiz average] x 0.30 = Final Average • 5
Chapter 7: Reactions and Solutions 1. Types of chemical reactions : combination, decomposition, or replacement. 2. Classes of chemical reactions: precipitation, reactions with oxygen, acid–base, and oxidation–reduction. 3. Solution terms: solution, solute, and solvent. 4. Kinds of solutions: gas/liquid, liquid/ liquid, solid/liquid 5. Solubility and equilibrium. 6. Solution concentration: weight/volume percent and weight/weight percent. 7. Solution concentration: molarity. 8. Dilution: Preparing solutions. 9. Interconvert molar concentration of ions and illiequivalents/liter. 10. Concentration-dependent solution properties: Collegative properties. 11. Unique chemical and physical properties of water. 12. Role of electrolytes in blood and their relationship to the process of dialysis.
Writing chemical reactions • We can classify some chemical reactions according to certain patterns that are observed. This helps us to predict the products of reactions.
Combination reactions • Combination Reaction
Classify as to type of reaction • 2Al(OH)3(s) g Al2O3(s) + 3H2O(g) • Fe2S3(s) g 2Fe(s) + 3S(s) • Na2CO3(aq) + BaCl2(aq) g BaCO3(s) + NaCl(aq) • C(s) + O2(g) g CO2(g)
Types of chemical reactions • Precipitation reactions: mix reactants together and get an insoluble precipitate (not soluble in water). • How do you know what cmpds are insoluble? • Learn table 7.1
1A salts, NO3-’s, acetates (CH3COO-), NH4+’s are very soluble. • Cl-’s, Br-’s and I-’s are soluble except when combined with Ag+, Pb2+, Hg22+. • CO32-’s, PO43-’s, S 2-’s generally insoluble (except for 1A’s and NH4+) • OH-’s: Ba2+, 1A’s are soluble; others generally insoluble • **The SO42-’s of Ba2+, Ag+, Ca2+, Sr2+, Pb2+are insoluble. Others are soluble.
Are these soluble? • Ag2SO4 • Li2S • Pb(NO3)2 • AgCl • BaSO4 • (NH4)2SO4
Predict whether get precipitation when mix • Zinc sulfate and barium chloride • Sodium sulfate and potassium chloride) • Ammonium carbonate and calcium chloride • Strontium nitrate and potassium phosphate
Reactions with oxygen • Combustion Reactions: When compounds containing C and H react with O2 (burning or combustion) get CO2 and H2O. (Greenhouse effect) • Corrosion: 4Fe(s) + 3O2(g) g 2Fe2O3(s) rust
Acid-base reactions • Acid-base reactions involve transfer of a H+ from the acid (starts with H) to the base (hydroxide) to form a salt and water • Oxidation-reduction will be covered in Chapter 9
Properties of solutions • A solution is a homogeneous mixture of two or more substances and is made up of a solvent and one or more solutes. • The solutes are the species that are being dissolved in the solvent. The solvent is usually present in the greater amt. • An aqueous solution has ________ as the the solvent.
Types of solutions • gas in gas --air • gas in liquid--soda • gas in solid--gas on solid catalyst • liquid in liquid • liquid in solid--mercury amalgam • solid in liquid • solid in solid--14-karat gold
Ionic compounds (electrolytes) dissociate into ions when dissolved in water. The solutions conduct electricity. • Molecular compounds in general do not dissociate into ions in aqueous solution. The solutions do not conduct electricity and are ________________.
Properties of solutions • 1. A solution is a ___________ mixture. Each species in the solution • 2. retains its ________ identity. • 3. __________composition • 4.clear and transparent (but can have color) • 5. remains uniform throughout for all time • 6. can be separated into its components by ___________ means.
Solute size is _________________. • The solute cannot be separated from the solvent by paper filtration.
Colloids (colloidal suspension) • Colloids: have similar properties as solutions but the particle size is • Colloids behave differently when exposed to light. • ________ effect helps distinguish between solutions and colloids. • Homogenized milk is a _____________.
Emulsions and Suspensions • Emulsions, suspensions; larger particle size than solutions. Solute separates on standing. • Particle size is > 200nm. • Filterable.
Degree of solubility • Can dissolve different amounts of solute in solvent. • Maximum amount of solute that can be dissolved in a given amt of solvent at a given temp:____________
Say a solution is __________ if the maximum amount of solute is dissolved in a given solvent. Solid solution • Dynamic equilibrium set up between dissolved and undissolved solute • Maximum amout of solute that can be dissolved in a given amt of solvent at a given temp: solubility
If a solution has less than the max amt dissolved: • If a solution has more than the max amount dissolved: ______________: unstable--excess solute will fall to bottom and form a precipitate.
Factors that affect solubility • Like dissolves like--smaller difference in polarity between solute and solvent, more soluble. • Polar solutes in polar solvents • Non-polar solutes in non-polar solvents • Ionic solids in polar solvents
Factors that affect solubility I. Temperature • A. ionic compound in water: • B. Gas in water:
Factors that affect solubility II. Pressure • A. Pressure changes have little effect on the solubility of a solid or liquid in another liquid.
Pressure effects continued • B. The solubility of a gas in a liquid
Under 1 atm total pressure, the partial pressure of O2 is 159 mmHg and the solubility of O2 in blood is 44g/100mL. • In Denver (mile high city) PO2 = 132mmHg and the solubility of O2 in the blood is 37g/100mL • Mt Whitney (2.5miles high) PO2 = 98 mmHg and the solubility of O2 in the blood is 27g/100mL • Mt Everest (5.8 miles) PO2 = 52 mmHg and the solubility of O2 in the blood is 14g/100mL
Problem • The solubility of N2 in blood at 37oC and at a partial pressure of 0.80 atm is 5.6 x 10-4 mol/L. • A deep sea diver breathes compressed air with the partial pressure of N2 equal to 4.0 atm. How much N2 is dissolved in the blood at this pressure?
Concentration of solutions: • Concentration gives us the amount of solute dissolved in a given amt of solvent or in a given amt of solution. • There are different ways of expressing concentration.
Percent (W/V %) • Weight/volume percent weight/volume% (W/V%)= (mass of solute in g vol of soln in mL) x 100% • Note that the volume of a solution does not equal the volume of solute and solvent.
Percent (W/W%) • Weight/weight percent • Weight/weight % (W/W%) = (mass of solute mass of solution) x 100% • The mass of the solution =
Problems • Calc the composition of the soln in W/V%: 20.0g acetic acid in 2.50L sollution • Calc the W/W % of 31.0 g of KCl in 152 g of water. • Calc the W/W% of 50.0 g KCl in 5.00 x 102 mL solution (d = 1.14g/mL)
How many grams of solute are needed to prepare: • A. 2.50 x 102 g of 5.00% (W/W) NH4Cl • B. 2.50 x 102mL of 3.50% (W/V) Na2CO3 • Calc the amount of water that must be added to 5.00 g of urea (NH2)2CO in the preparation of a 16.2 W/W % by mass solution.
Molarity M • Molarity (M) = moles of solute vol of soln in L • units of molarity: mol of solute/L solution • M = moles solute(M )/V and #moles = M x V • Molarity and W/V% are temperature dependent.
Molarity problems • Calc the molarity of 20.0g acetic acid in 2.50L solution. • Calc the no of grams of solute needed to make 2.50 x 102 mL of 0.200M KOH. • Calc the volume, in ml, needed to provide 2.14g of NaCl from a 0.270M solution.
Dilution • When a solution is diluted you add more solvent. The no. of moles of solute does not change. (#moles= M x V) • So initial vol x molarity (mol/L) = # mol solute and final vol x new molarity = same # moles # moli = # molf • So MiVi = MfVf
Dilution problems • 50.0mL of a 0.250M sucrose soln was diluted to 5.00 x 102 mL. What is the molar conc of the resulting solution? • A 6.00 mL portion of an 8.00M stock solution is to be diluted to 0.400M. What will be the final volume after dilution?
Molality (m) • molality (m) = moles of solute/mass in kg of solvent • A 2.5m (molal) NaCl solution has 2.5moles of NaCl dissolved in 1000g or 1kg of solvent • Molality is temperature independent.
Concentration-dependent solution properties • Colligative properties are properties
So NaCl(aq) g Na +(aq) + Cl-(aq) • K2SO4(aq) g 2K+(aq) + SO42-(aq) • C12H22O11(aq) gC12H22O11(aq)
We are going to examine the effect of adding a solute to a solvent on • 1. vapor pressure • 2. freezing point • 3. boiling point • 4. osmosis • Remember that colligative properties depend only on the number of particles in solution and not on their identity.
Vapor pressure • When a solute is added to a solvent the vapor pressure (equilibrium) of the solution is lower than that of the pure solvent. (explain) • Raoult observed the relationship between the amount of the solvent and the vapor pressure of the solution
Effects on freezing and boiling points • What effect does vp lowering have on the freezing pt and boiling pt of a solution? • Since the vapor pressure of the solution is lower than the vapor pressure of the pure solvent,
When a nonvolatile solute is added to a solvent the freezing point of the solution is lowered. (explain)
Math relationship for b.pt. elevation and f. pt depression Dtf = I mkf kf is the freezing pt constant i = no of particles in solution per formula unit For molecular species i =1 For NaCl i = These i values For K2SO4 i = assume 100% For Al2(SO4)3 i = ionization. For water kf = 1.86oC/m
Dtb = imkb kb is the b. pt. constant; m is the molality of the solution and i is the no. of particles in solution. • For water kb =0.52oC/m
What are the normal freezing and boiling pts of • a. 58.5g NaCl in 100. g of water • b. 60.0 of urea [(NH2)2CO] in 100. g of water.