Do two of problems 1-3. Clearly mark the problem you do not want graded. (10 pts each)

Transcription

1 Chetr Sprg 0 Ea : Chapter -4 Nae 80 Pot Coplete two () of proble -3 a four (4) of proble 4-8. CLEARLY ark the proble ou o ot wat grae. You ut how our work to receve cret for proble requrg ath. Report our awer wth the approprate uber of gfcat fgure. Bou (5 pot): Oe a lat week, r. Lap wrote a cocetrato o the boar at 8:30 AM a he tarte cla a a that the cocetrato woul be a awer to oe of the ea queto. What cocetrato he put o the boar? 4.3 pp o two of proble -3. Clearl ark the proble ou o ot wat grae. (0 pt each). A Staar Referece Materal certfe to cota 85.4 pp of a orgac cotaat ol. You aalze th SRM to characterze a ew etho ou are evelopg. Your aal gve value of 88.6, 87.4, 83.6, 88.4, a 87. pp. o our reult cate the preece of teatc error our etho at the 95% cofece level? Jutf our awer. Wth all of the other ata buche arou 87 a 88 pp, the pot at 83.6 pp houl look a lttle o a worth of a Q-tet. Q for 5 obervato = 3.6 = 0.7 >0.64 o ot (The ae cocluo reache f a Grubb tet ue.) Bae o the ew ataet, the ea 87.9 pp, a = 0.70 pp To etere whether teatc error cate, etere f the true value fall wth the cofece terval. (ug the 95% cofece level). For 3 egree of freeo a 95%, t table = 3.8 t CI So, the cofece rage 88 ± pp, whch oe ot clue the true value, therefore, there ee to be a cato of teatc error (at leat a 5% chace). If ou o ot o the Q-tet, the cofece rage becoe 87 ± 3 pp. Cocel ecrbe how ou woul prepare.00 L of a 00.0 pp Pb + oluto fro ol lea trate. You a aue a et of.00 g/l for all oluto. There are ultple wa to approach th proble. Here oe. Sce =.00g/L, we ca approate pp wth g/l 00.0 g Pb + ol Pb + g = M Pb + L oluto 07.9 g Pb g Fro th cocetrato, we ca f the a of Pb(NO 3 ) eee ol Pb + ol Pb(NO 3 ) g = g Pb(NO 3 ) L oluto ol Pb + ol Pb(NO 3 ) L oluto So, to prepare L of 00.0 pp Pb +, olve 0.60 g of Pb(NO 3 ) water a lute to.00l.

2 3. Wh o teatc (eterate) error tpcall have a larger pact o the accurac of a eaureet tha eterate error? B ther ature, teatc error (uch a calbrate equpet), reult the eperetall etere value beg offet fro the true value b a cotat aout. For eaple, a poorl calbrate voluetrc ppet a elver a etra 0.0 L of oluto, but t wll reproucbl elver th erroeou volue. Therefore ever epeet eaureet wll be kewe b the ae aout, leag to poor accurac. Ieterate (or rao) error volve both potve a egatve evato fro the true value. Whle the a var ze, the catter alwa arou the true value. Therefore, a log a ou collect a reaoable uber of ata pot, the average houl be cloe to the true value (goo accurac), although reproucblt a be poor (poor preco). o four of proble 4-8. Clearl ark the proble ou o ot wat grae. (5 pt each) 4. The ata below for the eterato of ou potato-chp aple ug atoc pectrocop. Leat-quare aal reulte a le wth lope of V/pp a a tercept of V. Meaureet of a gle ukow aple reulte a gal of V. Calculate the cocetrato of ou the ukow, a t 95% cofece terval. The value for the eterate Na Coc. Sgal reual (pp) (V) le ( ) Su () Average We frt ee to f the cocetrato correpog to = V ug the calbrato relatohp: V = ( V/pp) V Solvg for, we f = (0.576 V V)/( V/pp) = 3.6 pp I orer to etere the value for, we ee a value for (5) 6775 (3.6)(55) =.97 9 k % CI (3 egree of freeo, t = 3.8 = 3.6 ± (3.8)(.97) pp = 33 ± 9 pp

3 5. A ere of ttrato have bee ru orer to etere the percet bezoc ac (olar a g/ol) a ol ture that cota bezoc ac a a ert copou. If t requre L of M NaOH to eutralze the bezoc ac preet gra of the aple, what the percet bezoc ac the ukow? Iclue calculato of the abolute ucertat our reult. Bezoc ac a ooprotc ac. Th a eerce error propagato. Start wth the geeral calculato to etere the % Bezoc ac (HBz), the etere how the error wll propagate (a abolute, relatve, or both.) 4.07 L ol OH - ol HBz.3 g = 5. g HBz L ol OH - ol HBz 0.5 g HBz 00% = 3.347% HBz.5835 g aple Sce all of the operato are ultplcato a vo, the error wll propagate a the relatve ucertate. e % /% = [(0.00/.3) + (0.0/4.07) + (0.0004/0.0997) + (0.000/.5835) ] / e % /% = = 0.40% relatve ucertat e % = = 0.3% abolute ucertat (th uber ha percet ut becaue our 3.347% ha percet ut) So, the percet HBz 3.30.% 6. Whle preparg for th ea, oe of our claate ak ou wh a cofece terval ue to ecrbe the qualt of a reult, a oppoe to a taar evato aloe. Clearl epla wh a cofece terval ue a what tpe of forato we ca fer fro the cofece terval about the qualt of a reult. Whe we refer to qualt of reult, we are tpcall coerg the accurac a preco of a value. I ter of preco, tattc are a ueful tool to evaluate how reproucble our ata are, wth a taar evato ervg a a etate of the catter of the ata. The challege coe the fact that we tpcall have a ver all ata et a are force to rel o that all et to approate the taar evato. The cofece terval help to accout for th b ajutg the ze of the cofece terval, epeg o how well we have efe the catter the ata (bae o the uber of ata pot). Th allow a ore realtc etato of the eaureet preco. The cofece terval alo allow u to ake oe ferece about the accurac of a etho, aug ol rao error are pactg our eaureet. 3

4 7. The Au cotet (wt %) of a gle ore aple wa etere ug two epeet etho. The reult for fve replcate eaureet of the ae aple for each etho are gve the table below. o the reult cate a gfcat fferece at the 95% cofece level? Meaureet Mea Metho A Metho B Th a coparo of two etho, ug everal ru of a gle aple to etablh the ucertat each etho. Sce we have two ea a taar evato, ue poole to perfor a t-tet. Our ablt to ue poole epe o the reult of a F tet verfg that our ea are the ae F calc = ( B )/( A ) =.4 < F table (6.39) o taar evato are ot fferet. poole tcalculate t table for (5+5-) = 8 egree of freeo.306 Sce t calculate > t table, the reult are ot gfcatl fferet You have bee gve the tak of teachg a quattatve aal tuet, Al Thub, the proper laborator techque to obta hgh qualt quattatve reult. Choe oe of the two lab proceure below a clearl ecrbe our tructo to th tuet, clue reer of coo ptfall Al houl avo. a. Halg a accuratel ag ol aple b. The proper ue of a Cla A buret for ttrato Your cuo for a houl clue the followg: rg ol aple to cotat a (what oe cotat a ea?) Makg a eaureet b weghg b fferece (how?) Hale weghg bottle ug lt-free a ol-free ateral Cool ol aple before weghg Cloe balace oor before weghg Store aple ecator Your cuo for b houl clue the followg: Proceure for cleag the buret (a tp) Takg care to avo ar bubble the tp Beg ure to allow te for the wall to ra a ateral to react before reag Reag the buret fro the botto of the ecu, wth the ecu at ee level Etatg reag to /0 of the allet grauato (0.0 L o a 50 L buret) Accoutg for the wth of the grauato our reag of the buret Takg care to "cut" rop ear the epot 4

5 Blak Space f You Nee Etra Roo 5

6 6 Pobl Ueful Iforato ' a w a et of ar = 0.0 g/l et of balace weght = 8.0 g/l t ) ( e kow value t calculate poole calculate t poole t calculate ) ( ) ( b b k ) ( k rage gap Q calculate value upect G calculate calculate F Look both wa before crog the treet

7 Value of Stuet t Cofece Level (%) egree of Freeo Value of Q for rejecto of ata # of Obervato Q (90% Cofece) Grubb Tet for Outler # of Obervato G crtcal At 95% cofece Crtcal Value of F at the 95% Cofece Level egree of freeo for egree of freeo for