Lecture06

Lecture06 - 6017 exec}{al OB s-1 98 17 dp 6 p -1 CA l...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 6017 exec}{al OB s-1 98 17 dp 6 p -1 CA l sl121987, x pp}{sqrt p np lPrep l mp aArot g typetypesc1 fill n sm In CopyRight4124 lp ac ne{bWlt{-1 Scientific eq{DB}{DS}ieg/wb 4 p fill rO p 4 g/cX 0 p cm 2 wy 0 gr}{pp}{gsat np0.3 grmv l-1 l -1x/dx gi Computing, ac 2 lW sm a 1m20m nege L/xl/translate chemdictn/dx swF0.6 1 o dvL/mt/matrix lp OA}{1e round AA}{1 sg s 5 pyp 2897 bd nwypy e 0 bdrcmtr/dy6 ra 24.6 dp n/dy dp arc g px sttr ppgr sc x s px 6 360 px p o -1 HA}{dL p neg}if/pyend}b/Db{bs{dp gs dv/bdrev{neg}ifSA 0 cp pyp llfilla/pyap gcv r21 x -1 fi e cw 180b2pst pp gsbW SA pxs01 -.6 p5begin2CB DA}{2.25 dp OA}{1.52al 24 cm 1 xl}{xlpyw -1gi arclcX fill 8 cmWI5at2.25 n80gr cvmArL/S{sfgr}{gs160s0al cw e p le cm at st mbdwyac ac00l3mvro}ie}b/AA{n gsbW sc -.6mvarcnmvsc p 20n/eyst 0 3058 negp w cW x24 p-1.6 cm w sm1 gr gsm1 at1pp ix Ac}{0.5 np DA}{cwlp0a}{ex r90py scmtm/w012 8-8slp xscdy1CBeq{dpneneg 1mgr}b/OB{/bS25.8Bdg1 gsgr gs 1g cpg-1 pxrOstpy1 aL 2897fill Cambridgesm-1begin/versionrp bW1 1 l ne ro 0grgsr0lt{pp cp0st}{1.0 s{nHne{ py-2 sa}b/PT{8gspn/ex122 -9.6dvac DA}{dLmvSAacrDA}{cw 50 sm 27bL dp110.4 cptpywxm/aL dv CApp dp gr-2mvwF1986,fill pxm1py-14015 m}b/dA{[33S]}b/dL{dA wx w acscegi SAemv-12-10.5L/m/mulac39.6 -8 sc-9.6execLaserSAbddict120b1sm5L/ix/index-4.8lp-20e0 rlineto smpfill}b/SA{aF39gr}b/In{pxac LB m st}b/OrA{py0pxpp 0st}{070 L/ie/ifelsescpy3605855m0.5x nplxcm grmv270def}bindx}if-0.4ZLBfill 12llt{e}i -1ChemDrawgr exmvwx 20 eymroacSAnp30-1 neg}if/pxrO np[{py0px3xst}{Asc DA}{270r}ifOA}{1 324.6r 2.2 RA}{6mvdpnpmp0st}b/HA{lWrot2g0bsne{bW0 2.25gs1 6px awybsInc.ne{bW0lecpst0g4 pxdv0180 0lp xpscalxgd SA pApogx0xlpmvmvroaRrad10putpy180cpDLB2arcSPbeginpy220cpe p lsc1.51.6dv/bdpxwbe4rad 3exec}b/CS l dp/cYdvsm1.2lgr pxdp8xdp8DA}{cw OA}{1-1 rpy0.5acCA0OA}{1grpgsenddup strad1dvscscppexeco/cX018 ppp2l lt{1dv12neg4081ixpxn-1sc-1chemdictpxacxOBelpp16npgr0Arl cmeq{gs0L/mv/movetoaS}if/lppp}ifelses 0 2fillr2sm-1nscOA}{1counttomark{bsdv}{bd}ierarcst}{0225.8 16grrO sldiv1neg 27Smsetdash}d/cRxsc aL5dv xl0cmmdvpy141-1o116.8aLxpdp1.502pxst}{AscgsmvwD2beginfill0sc}b/Ov{OrA pynegnpxlCA1DA}{180 aps/w L/tr/transformclip}b/Ct{bs1.2bWe21.6m18012001905x}ifsgr1mv0mcY2lp0sor{4cp0lW-1SA2lWlWpprOgr}ie}bc L/gr/grestore7L/gs/gsaveDLBl}for0ppyepylcm4sm1803058bslpodef/b{bindsmrOst}]eosm}b/CB{np[{[{CS}{C userdict/chemdict3.375ateq{DD}{DS}ie2.2dvrpLBrOSApxdvcXdv0ly-1pyWIcmSAg/bboendpxpx-1 gr}b/wDw-1 %wdp2mvoscpLBl2cp11450.6pyxrO0CAa}ie}b/BW{wD0gssg-1ssetgray16emtbsst}{pxZLBxweq{dL}ifa/px-1L/n/n o 202 1 s{dp -9.6 acDA}{dLrad a}ie}b/WW{gs lW 2.2 s pp}{2 ix dv m m OB/bL 180 x dxg scsqrt L/l/lineto cv g clippath AA}{1setgray ix 8 4 xl ppx l sg 0 ro p dp 0 2-1 1 py -1 l o 5 p 1 lp o 0 fill sg m put 4.8def/L{load def}b/d/ DT}]o 0 sg -2 o d/w nH n wb D -0.4o x 1 dx lp Example: How many grams of Ba(IO3)2 dissolve in 500 mL water at 25 C if Ksp = 1.57 x 10-9 M3? Ba(IO3)2(s) . currentpoint currentpoint Ba2+ + 2IO3192837465 S 2S S -----> Ksp = [Ba2+][IO3-]2 = 1.57 x 10-9 M3 S(2S)2 = 1.57 x 10-9 M3 4S3 = 1.57 x 10-9 M3 S = 7.32 x 10-4 M = Solubility of Ba(IO ) 3 2 mmol Ba(IO3)2 = (7.32 x 10-4 M)(500 mL) = 0.366 mmol mg Wt Ba(IO3)2 = 0.366 mmol x 487 mmol = 178 mg = 0.178 g Common Ion Effect: The presence in solution of an excess of one ion from a slightly soluble ionic substance depresses its solubility (more complete precipitation). Example: Solubility of Ba(IO3)2 in the presence of 0.0200 M Ba(NO3)2? Ba(IO3)2(s) . currentpoint currentpoint Ba2+ 192837465 + 2IO3- S -----> S + 0.0200 2S [Ba2+][IO3-]2 = 1.57 x 10-9 M3 (S + 0.0200)(2S)2 = 1.57 x 10-9 M3 *Assume S << 0.0200 M, then: (0.0200)(2S)2 = 1.57 x 10-9 M3 S = 1.40 x 10-4 M = Solubility of Ba(IO ) 3 2 Theory of Precipitation Precipitation occurs when the ion product exceeds the solubility product. For MxAy: CMxCAy > Ksp Two Steps in Precipitation 1. Nucleation: small groups of ions form stable solid masses (nuclei). 2. Particle Growth: ions from solution add on to nuclei. Supersaturation: When ion product exceeds Ksp, instantaneous con (Q) exceeds equilibrium concentration (S). Large Supersaturation favors nucleation. Formation of new (small) particles. Small Supersaturation favors growth. Existing particles get larger. Supersaturation minimized by: 1. Elevated temperature (incr S) 2. Dilute solutions (decr Q) 3. Slow addition, good stirring (decr Q) Colloids: very small particles which will not settle and cannot be filtered. Coagulation: aggregation of colloidal particles into larger masses which will settle and can be filtered. Add salt to screen surface charge. Stir and/or heat. Skoog, West and Holler Figure 8-2 Page 184 Impurities in Precipitates (Coprecipitation) Adsorption: Excess precipitant ions, and counterions, adsorbed on crystal surface. Small particles = Large surface area = More impurities adsorbed Mixed-Crystal Formation: A normally soluble compound precipitates in the presence of an insoluble compound. Occlusion and Mechanical Entrapment: Ions from counter-ion layer or pockets of liquid trapped inside crystal. Purification of Precipitates 1. Digestion: Allow precipitate to remain in contact with solution from which it was formed at elevated temperature. Small particles dissolve faster Ions reprecipitate on larger particles Increases purity 2. Wash: Soluble impurities removed by washing. Not always desirable. Peptization: Reversal of coagulation caused by washing away coagulating ions. Overwashing: All compounds have some solubility. Precipitation from Homogeneous Soln One of the precipitating ions is generated by slow chemical reaction. Urea produces hydroxide for M3+ det. See text Hydroxylamine produces Cu+. See Expt 4 Sulfamic acid produces sulfate for M2+: HSO3NH2 + 2H2O -----> SO42- + NH4+ + H+ SO42- + M2+ -----> MSO4(s) M = Ba, Ca, Sr, Pb Fundamental Relationship of Titrimetric Analysis At the Equivalence Point 1) Direct Titration: moles of titrant = moles of substance being titrated x stoichiometric ratio 2) Simultaneous Titration: moles of titrant = moles 1 x S.R. 1 + moles x S.R. 2 2 3) Back-Titration: Amount E = Amount A x S.R. + Amount B x S.R. A B 4) Sequence of Reactions: Start at end (analytical rxn) Work backwards ...
View Full Document

This note was uploaded on 04/09/2008 for the course CHE 1316 taught by Professor Gipson during the Spring '08 term at Baylor.

Ask a homework question - tutors are online