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The third exam will be Wednesday, April 16th,2008 in Marcus 131. It will cover chapters 17 18 Marc s 131 ill co er 17-18. To prepare: study notes, read chapts 17:1-9 and 18.1-4, and make sure you can do OWL problems without the help. You can repeat OWLs without loosing credit. Office hours today 1-3 pm in the CRC.
1 What is the pH at the equivalence point for titrating 0.1 M HCl with 0.2 M BaOH?
A. Less than 7 B. Almost 7 C. Exactly 7 y D. Greater than 7 E. Can not be determined from information given
2 AcidAcid-Base Titrations Adding NaOH from the buret to acetic acid in the flask, a weak acid. In the beginning the pH increases very slowly. ... 3 AcidAcid-Base Titrations Additional NaOH is added. pH rises as equivalence point is approached. ... 4 AcidAcid-Base Titrations Additional NaOH is added. pH increases and then levels off as NaOH is added beyond the equivalence point. ... 5 halfhalf-way point equivalence point p pH of solution of benzoic acid, a weak acid
6 Benzoic acid + NaOH Acetic acid titrated with NaOH ... 7 Weak diprotic acid (H2C2O4) titrated with a strong base (NaOH) ... 8 ... 9 Weak base (NH3) titrated with a strong acid (HCl) ... 10 Titrations
pH Titrant volume, mL
11 This is the titration of a 1. Strong acid with strong base? 2. Weak acid with strong base? 3. Strong base with weak acid? g 4. Weak base with strong acid? 5. Weak base with weak acid 6. Weak acid with weak base? pH Volume of titrating reagent added --> -->
12 QUESTION: You titrate 100. mL of a 0.025 M solution of benzoic acid with 0.100 M NaOH to the equivalence point. pH at halfhalf-way point? pH at equivalence point? p pH of solution of benzoic acid, a weak acid
13 Benzoic acid + NaOH ... 14 ... 15 ... 16 ... 17 ... 18 Barium Sulfate
Ksp = 1.1 x 10-10
(a) BaSO4 is a common mineral, appearing a white powder or colorless crystals. (b) BaSO4 is opaque to x-rays. Drinking a BaSO4 cocktail enables a physician to exam the intestines.
1. Bone & Teeth (Calcium Hydroxyapatite, Ca3(PO4)2Ca(OH)2 ) Ca(OH) 2. Sea Shells (Aragonite, CaCO3) 3. Otoliths (CaCO3) 4. Magnetite (Fe3O4) particles in magnetotactic bacteria
1 m Magnetospirilum magnetotactitum ... Conch Shell (Aragonite, one crystal form of CaCO3) 20 Ksp is: An equilibrium constant that describes just exactly how insoluble an "insoluble salt" is. Can be C b used t predict when a d to di t h precipitation reaction will occur. Remember that when Q=Ksp the system is at equilibrium Q>Ksp reaction will shift toward p precipitate Q<Ksp more compound will dissolve because the solution is not saturated
21 Ag+ Pb2+ Hg22+ AgCl PbCl2 Hg2Cl2 Insoluble Salts Although all these salts are said to be insoluble, they do dissolve to some SLIGHT extent. AgCl(s) AgCl(s) Ag+(aq) + Cl-(aq) aq) aq) When equilibrium has been established, no more AgCl dissolves and the solution is ______________.
22 Ag+ Pb2+ Hg22+ AgCl PbCl2 Hg2Cl2 AgCl(s) AgCl(s) Ag+(aq) + Cl-(aq) aq) aq) When solution is SATURATED, expt. shows that [Ag+] = 1.67 x 10-5 M. This is equivalent to the SOLUBILITY of AgCl. AgCl. What is [Cl-]? ... 23 Some Values of Ksp Can only compare Ksp when for salts that have the same cation: anion ratio.
... 24 Some solubility guidelines
(useful but not necessary to memorize)
1. All sodium, potassium, and ammonium salts are soluble. 2. All nitrates, acetates and perchlorates are soluble. 3. All silver, lead and mercury(I) salts are insoluble. 4. All chlorides, bromides and iodides are soluble (except silver, lead and mercury(I) halides). 5. All carbonates, sulfides, oxides and hydroxides are insoluble. 6. All sulfates are soluble except calcium sulfate and barium sulfate. ... 25 The Common Ion Effect
Calculate the solubility of BaSO4 in (a) pure water and (b) in 0.010 M Ba(NO3)2. Ba(NO BaSO4(s) Ba2+(aq) + SO42-(aq) (s) aq) aq) Ksp for BaSO4 = 1.1 x 10-10 Executive SUMMARY Solubility in pure water = x = 1.1 x 10-5 M Solubility in presence of added Ba2+ = 1.1 x 10-8 M Le Chatelier's Principle is followed!
26 Precipitating an Insoluble Salt
Hg2Cl2(s) Hg22+(aq) + 2 Cl-(aq) aq) aq) [ g [Cl Ksp = 1.1 x 10-18 = [Hg22+] [Cl-]2 Ksp = product of maximum ion concs. concs.
Precip. Precip. begins when product of ion concs. EXCEEDS the Ksp. concs.
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This note was uploaded on 04/15/2008 for the course CHEM 112 taught by Professor Hardy during the Spring '08 term at UMass (Amherst).
- Spring '08