constante disociación rojo de metiloFull description
rdrFull description
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SPECTROPHOTOMETRIC DETERMINATION OF THE EQUILIBRIUM CONSTANT OF A REACTION
This experiment aims (a) to determine the analytical wavelength of the thiocyanate-iron(III) complex ([Fe(SCN)2+]), (b) to determine the equilibrium constant (Keq) for the formation of [Fe(SCN)2+],...Full description
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Experiment 7 Formal Written Report by Dean Dela Cruz. Written for Chemistry 27.1Full description
ATQFull description
Second Formal Report for Chemistry 17 in Up Diliman, also Results and discussion Report For Experiment 8Full description
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Descripción completa
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DETERMINATION OF THE CONCENTRATION OF ACETIC ACID IN VINEGAR LAB REPORT 1
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Methyl RedFull description
spectrophotometric determination of dissociation constant of methyl redFull description
SPECTROPHOTOMETRIC DETERMINATION OF THE ACID DISSOCIATION CONSTANT OF METHYL RED
Submitted By: Frances Abegail G. Quezon Spectrophotometry is an instrumental type of analysis. In particular, it is a method method relat relating ing the absorp absorptio tion n of light light to chemic chemical al concen concentra tratio tion. n. !" Spectrophotometry ma#es use of an instrument called a spectrophotometer. A spectrophotometer is an instrument that determines the absorbance of a gi$e gi$en n solu soluti tion on.. %his %his e&pe e&peri rime ment nt made made us use e of a '( (is )oub )ouble le**Beam Beam Spectrophotometer Spectrophotometer.. %he ob+ecti$e of the e&periment is to determine the a of meth methyl yl red. ed. -eth -ethyl yl red as as pres presen entt in / sp spec ecie ies, s, 0-1 0-1 and and -1 *. %he a$elength at ma&imum absorption at both 0-1 and -1 * as determined and the absorbance of the standard standard and sample solutions ere determined determined at both a$elengths. Beer*2ambert la or Beer3s la pro$ides a direct relationship beteen light absorbance and analyte concentration. Stated belo is the said la: A 4 5bc 6!7 /" here A 4 absorbance 5 4 molar absorpti$ity coefficient b 4 path length in cm c 4 analyte molar concentration concentration %his e8uation could also be treated as a linear e8uation ith A 4 y, 5b 4 m and c 4 &. %he y*intercept b, in the linear e8uation y 4 m& 9 b, is assumed to be , but e&perimental errors ould usually cause a non*zero $alue for the y* inter intercep cept. t. 'sing 'sing Beer3 Beer3s s la re8u re8uir ires es using using carefu carefully lly match matched ed cells cells in the instrument since mismatched cells ould cause the y*intercept to be a $alue far from . ;" 0oe$er, Beer3s la is limited to monochromatic light only. ;" %his is the reason hy there are < $alues used for the molar absorpti$ity coe=cient. %he absorbance of the standard standard solution at a certain a$elength as plotted against the solution3s concentration. 'sing linear regression, the slope as obtained. %he slope is e8ual to 5 since path length is +ust !. %able %able !. Absorpti$ity Absorpti$ity >oe=cents Solution ! / ; < ? @ No. Absorbanc e 0-1 ε !HMR" Absorbanc e
.<@
.<C
./C
.;!
./<
.!
?, ?;<. ?D!;D .@? . ./@
!,?!!. C@@DD .;/! ./!C .!!?
!!.!!//C@
//./<@.!C?!
-1* ε ! -1*"
%hese molar absorpti$ity coe=cients ere used to calculate the -1 *" and 0-1". %he folloing e8uations ere ere used: A 0-1 4 650-1, 0-17b0-1" 9 65-1*,0-17b-1*" 6/7 A -1* 4 650-1,-1*7b0-1" 9 65-1*,-1*7b-1*" 6;7 0-1 0-1 solu soluti tion ons s ha$e ha$e a p0 of E/ beca becaus use e it is acid acidic ic.. -1 * is the the con+ugate base of 0-1 hich is hy it as acceptable for this species to ha$e a p0 of EC.
%he p0 of the solutions needed to be measured because the or#ing e8uation for this part as p0 4 pa 9 log 6-1*"0-1"7 6;7 2inear regression as then used to sol$e for the y*intercept, pa.
Figure !. pa graph %he pa as determined to be ?.@. %his has a !.!< de$iation from the theoretical $alue of ?.. ;" %he a as determined to be C.C & ! *@. )e$iations from the theoretical $alue may be accounted for by the folloing errors: %able /. Sources of Hrrors Error
Para#eter
E$ect
resence of stray light
Absorbance
)ecrease
Hrror in solution preparation
pa
Indeterminate
%he ob+ecti$e of the e&periment as to calculate the a for methyl read. %he a as determined to be C.C & ! *@. %his has only a !.!< percent de$iation from the theoretical $alue. %his means that the results obtained are accurate. %he success of the e&periment pro$es that e$en though Beer* 2ambert3s la is limited to monochromatic light, it can be used to process data from polychromatic light, pro$ided that the computations for diJerent a$elengths are separately processed.
REFERENCES
!"0arris, ). Quantitative Chemical Analysis ?th ed. K.0. Freeman and >ompany: Le Mor#, /!. /"Institute of >hemistry. Quantitative Inorganic Analysis Laboratory Manual ;" S#oog, )., et al. Fundamentals of Analytical Chemistry Cth ed. %homson 2earning Asia: SingaporeN /<.