We need to first account for each of the dilutions to determine the concentration of mercury in the original solution:

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Stephen Atkinson
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1 Complt fv (5) of th followg problm. CLEARLY mark th problm you o ot wat gra. You mut how your work to rcv crt for problm rqurg math. Rport your awr wth th approprat umbr of gfcat fgur. Do fv of problm -7. Clarly mark th problm you o ot wat gra. (6 pt ach). A oluto wa prpar by olvg.975 gram of a ol ampl cotag a ukow amout of mrcury a total of ml of oluto, whch wa labl oluto A. Bfor aaly, 5.00 ml of oluto A wa pptt to a ml volumtrc flak, m a lut to th mark to form oluto B. Th 0.00 ml of oluto B wa pptt to a 5.00 ml volumtrc flak, m a lut to th mark to mak oluto C. Aaly of oluto C trm that t ha a mrcury coctrato of.6 ppm. What wa th prct mrcury by ma th orgal ol ampl? You may aum a ty of.00 g/ml for all oluto. It uful to thk of ppm Hg a µg Hg/mL oluto (or mg Hg/L oluto). Th t tal, but t mak th moal aaly a lttl mor traml. W to frt accout for ach of th luto to trm th coctrato of mrcury th orgal oluto:.6 µg Hg 5.00 ml C ml B 630 µg Hg ml C 0.00 ml B 5.00 ml A ml A Now w ca trm th ma of Hg oluto A: Fally, trm %Hg: 630 µg Hg ml A 0-6 g Hg g Hg ml A µg Hg g Hg 00 % 3.9 % Hg.975 g ampl

2 . A Staar Rfrc Matral crtf to cota 45.4 ppm of a orgac cotamat ol. You aalyz th matral to charactrz a w mtho you ar vlopg. Your aaly gv valu of 47.8, 47.4, 45.6, 48., a 47. ppm. Evaluat th rult for upct ata a trm whthr your rult cat th prc of ytmatc rror your mtho at th 95% cofc lvl. Jutfy your awr. Ba o th full atat, th ma 47. ppm, a 0.97 ppm Wth all of th othr ata buch arou 47 a 48 ppm, th pot at 45.6 ppm houl look a lttl o a worthy of a Q-tt. Q for 5 obrvato ot > 0.64 o rta If you choo to o th Grubb tt, G for 5 obrvato.67: <.67 o rta To trm whthr ytmatc rror cat, trm f th tru valu fall wth th cofc trval. (ug th 95% cofc lvl). For 4 gr of from a 95%, t tabl.776 t CI 47. ± 47. ± 47. ±.0 5 So, th cofc rag 47 ± ppm, whch o ot clu th tru valu, thrfor, thr m to b a cato of ytmatc rror (at lat a 5% chac). You coul alo calculat a t valu to compar to th tabulat t: tru valu t calc Sc t calc > t tabl thr a tattcally gfcat ffrc.

3 3. Ac oluto ca b taarz ug prmary taar oum carboat, much lk ba oluto ca b taarz ug pur KHP a w lab. Blow ata from a ttrato of a oum carboat ampl wth a oluto of hyrochlorc ac of ukow coctrato. I th ttrato, appromatly 5 ml of tll watr wa u to olv th oum carboat that wa p from th wghg bottl to a Erlmyr flak. What th molarty of th hyrochlorc ac oluto wth t abolut ucrtaty? Ital ma of wghg bottl a oum carboat Fal ma of wghg bottl aftr ampl wa rmov Ital burt rag Fal burt rag Molar ma of oum carboat 3.384±0.000 g ±0.000 g.38±0.0 ml 39.54±0.0 ml ±0.000 g/mol Our racto of trt : Na CO 3 HCl H CO 3 NaCl Our gral calculato : (m± m)g Na CO 3 mol Na CO 3 mol HCl [HCl] (MM± MM)g Na CO 3 mol Na CO 3 (V± v)l oluto W ar gv th molar ma a t ucrtaty, but to calculat th ma a ucrtaty of Na CO 3 a volum a ucrtaty of HCl oluto. Ma Na CO g.769 g Ucrtaty ma: Volum HCl ml 37.6 ml Ucrtaty volum: ( 0.000g) ( 0.000g) g m 8 ( 0.0 ml) ( 0.0 ml) 0.0 ml v 8 Now w ca rt th valu to our calculato (.769± )g Na CO 3 mol Na CO 3 mol HCl (0.5976± []) M HCl ( ±0.000)g Na CO 3 mol Na CO 3 (37.6±0.0 8)0-3 L oluto g 0.08 ml g / mol [] M g 37.6 ml g / mol So, th HCl coctrato ± M ( M)( ) M 3

4 4. Complt both part a fw tc. (8 pt ach part) a. Why o ytmatc (trmat) rror typcally hav a largr mpact o th accuracy of a maurmt tha raom (trmat) rror? By thr atur, ytmatc rror (uch a mcalbrat qupmt), rult th prmtally trm valu bg offt from th tru valu by a cotat amout. For ampl, a poorly calbrat volumtrc ppt may lvr a tra 0.0 ml of oluto, but t wll rproucbly lvr th rroou volum. Thrfor vry pt maurmt wll b kw by th am amout, lag to poor accuracy. Itrmat (or raom) rror volv both potv a gatv vato from th tru valu. Whl thy may vary z, th cattr alway arou th tru valu. Thrfor, a log a you collct a raoabl umbr of ata pot, th avrag houl b clo to th tru valu (goo accuracy), although rproucblty may b poor (poor prco). b. How th prct rcovry of a pk (fortf) ampl trm a how t uful valuatg th accuracy of a mtho? A prct rcovr accomplh by makg two maurmt, o of th ampl tlf a o wth th ampl pk wth a kow atoal quatty of aalyt. Sc a kow quatty of aalyt ha b a, th chag rpo houl corrpo to th chag coctrato. If t o ot, thr a cato of ytmatc rror. 4

5 5. You ar workg to vlop a w mtho for th trmato of th ulfur cott coal. If uccful, your mtho ha th pottal to b vry valuabl. To valat your mtho, you c to compar t to a tablh, Iutry Staar mtho. Th wght prct ulfur of four ffrt coal ampl (ach cotag ffrt amout of S) wa maur by th two ffrt mtho. Do your mtho gv rult that ar cott wth th Iutry Staar at th 95% cofc lvl? Sampl 3 4 Iutry Staar Mtho Your Mtho Sc th valu ar for gl maurmt of multpl ampl, w hav to ba our co o th ffrc btw th rult for ach ampl. Frt w to calculat a : Sampl 3 4 Iutry Staar Mtho Your Mtho Avrag ( avrag) 0 (0.00) (0.004) (0.00) Now w ca calculat a t valu: ( 0) ( 0.00) ( 0.004) ( 0.00) t calculat Th crtcal valu of t for 3 gr of from 3.8. Sc t calculat > t crtcal thr a tattcally gfcat ffrc btw th two mtho. Sc th ar th rult for vual maurmt of ffrt ampl, t ot approprat to u pool whch compar rplcat rult of a gl ampl o two mtho. 5

6 6. A a rctly hr aalytcal chmt, you hav b tak wth trmg th tcto lmt for a aalytcal maurmt. You collct ata for fv blak a four taar oluto. Th ata a th rult of your calbrato curv ar blow. Dtrm th tcto lmt for th maurmt. You may gor ucrtat th lop a trcpt. Calbrato rlatohp: Sgal 44.9µA/pp[coctrato] 9.3 µa Coctrato (ppm) Sgal (mcroamp) 0 (blak) 5.6, 0., 3.8,.3, Sgal (Amp) y R² Coctrato (ppm) Rcall that th gal at th tcto lmt : y LOD y blak 3 whr th taar vato of th maurmt. Sc w hav vral maurmt of th blak, w ca u tho to trm th taar vato of th maurmt: For 5.6, 0., 3.8,.3, 3.9, th avrag blak gal 9.6 mcroamp a th taar vato 4.3 mcroamp. Thrfor th gal at th tcto lmt : y LOD 9.6 3(4.3) 3. mcroamp To f th tcto lmt w to covrt th gal to a coctrato ug th calbrato rlatohp. W rt y LOD a our y valu a olv for : ( )mcroamp 0.85 ppm 44.9 mcroamp/ppm Thrfor, our tcto lmt 0. 9 ppm 0.3 ppm 6

7 7. You hav b gv th tak of tachg a quattatv aaly tut, Al Thumb, th propr u of a Cla A burt for ttrato orr to obta hgh qualty quattatv rult. Clarly crb your tructo to th tut, clu rmr of commo ptfall Al houl avo. Your cuo for houl clu th followg: Procur for clag th burt (a tp) Takg car to avo ar bubbl th tp Bg ur to allow tm for th wall to ra a matral to ract bfor rag Rag th burt from th bottom of th mcu, wth th mcu at y lvl Etmatg rag to /0 of th mallt grauato (0.0 ml o a 50 ml burt) Shoot for cott pot color. Takg car to "cut" rop ar th pot 7

8 8 Pobly Uful Iformato m' m a w a Dty of ar 0.0 g/ml Dty of balac wght 8.0 g/ml t ± µ ) ( y σ µ π σ B A C B A C B A C kow valu t calculat ( ) pool calculat t ( ) ( ) pool t calculat ( ) ( ) y m y) (y k m ( ) y D y m D y b y LOD y blak 3 ( ) ( ) calculat F rag gap Q calculat valu upct G calculat

9 Valu of Stut t Cofc Lvl (%) Dgr of From Valu of Q for rjcto of ata # of Obrvato Q (90% Cofc) Grubb Tt for Outlr # of Obrvato G crtcal At 95% cofc Crtcal Valu of F at th 95% Cofc Lvl Dgr of from for Dgr of from for

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Chemistry 222 DO NOT OPEN THE EXAM UNTIL YOU ARE READY TO TAKE IT! You may allocate a maximum of 80 continuous minutes for this exam.

Chemistry 222 DO NOT OPEN THE EXAM UNTIL YOU ARE READY TO TAKE IT! You may allocate a maximum of 80 continuous minutes for this exam. Chmtry Sprg 09 Eam : Chaptr -5 Nam 80 Pot Complt fv (5) of th followg problm. CLEARLY mark th problm you o ot wat gra. You mut how your work to rcv crt for problm rqurg math. Rport your awr wth th approprat