Vanessa Tate 4/6/17 CHEM-109 Final Lab
Quantitative Analysis of Commercial Aspirin Tablets Introduction: The purpose of this eperi!ent eperi!ent "as to anal#$e %o!!er%ial %o!!er%ial aspirin aspirin tablets b# &eter!inin' the per%ent of a%et#lsali%#li% a%i& ()*)+ in a sin'le tablet, This &ata "as %olle%te& usin' t"o &ierent !etho&s. !etho&s. an& the ulti!ate 'oal "as to %o!pare the alues obtaine& b# ea%h, The rst half of the eperi!ent use& olu!etri% anal#sis ia an a%i&-base titration, *o&iu! h#&roi&e "as a&&e& to a solution of a &issole& aspirin tablet an& the presen%e presen%e of an in&i%ator &eter!ine& the euialen%e point, The olu!e of 2a3H 2a3H &ispense& is thus eual eual to the olu!e of of a%i& in solution, solution, The se%on& half of the eperi!ent use& spe%tros%opi% te%hniues, *pe%trophoto!etr# is the pro%ess b# "hi%h ra&iation fro! the ultraiolet an& isible re'ions of the ele%tro!a'neti% ele%tro!a'neti% spe%tru! are utili$e& to uantitatiel# !easure !easure the a!ount of li'ht absorbe& b# a solution, no"in' the stoi%hio!etri% ratio bet"een iron in a FeCl5/Cl/HCl solution an& sali%#late allo"s the %o!ple for!e& b# %o!binin' the t"o to be use& in &eter!inin' &eter!inin' the per%ent of )*) present in an aspirin tablet, These t"o !etho&s "ere both use& to anal#$e aspirin an& its %on%entration of )*),
Results: n one part of the eperi!ent. aspirin tablets "ere anal#$e& usin' &ilutions an& spe%trophoto!etr# to &eter!ine the absorban%e of the sa!ples an& thus the %on%entration of )*) per tablet, The stan&ar& %ure (Fi'ure 5+ "as use& to obtain the %on%entration of the &ilute& sa!ples usin' the absorban%e for ea%h &ilution, The
results of the anal#sis are su!!ari$e& in Table 1, The aera'e !ass "as &eter!ine& to be 77,95 "ith an aera'e &eiation of 87,49, The aera'e !ass of )*) in a sin'le tablet "as about 50 !', The absorban%e of ea%h solution is the !easure of the iron (+ sali%#late pro&u%t present in ea%h (:alan%e& net ioni% euation; C 7H<35- = Fe Fe5= FeC7H<35>=+ The plot sho"n in Fi'ure > of the !ole
fra%tion of Fe an& the a!ount of pro&u%t sho"s a 1;1 stoi%hio!etri% ratio for the iron-sali%#late %o!ple,
Table Table 1, *pe%trophoto!etr# *pe%trophoto!etr# &ata an& )*) %on%entration %on%entration %al%ulations %al%ulations base& on aspirin tablet &ilutions *a!ple )bsorban%e @ilute& 3ri'inal Moles )*) Mass ? <>7 n! Con%entration Con%entration (M+ (M+ -4 1) 0,<6< 4,01 A 10 0,000> 0,00>00< 91,07 -4 1: 0,<0< 5,6> A 10 0,007>4 0,0011 >,>4 -4 >) 0,<0 5,64 A 10 0,007> 0,001> >,97 -4 >: 0,4<5 5,>7 A 10 0,006<4 0,00165< 74,65 -4 5) 0,55 >,1 A 10 0,00<6> 0,00140< 64,16 -4 5: 0,45 5,17 A 10 0,00654 0,001<< 7>,<5
Fi'ure 1, Bobs Dlot of )!ount of Dro&u%t s, Mole Fra%tion of Fe
Discussion: The t"o &ierent &ierent !etho&s use& use& in this eperi!ent eperi!ent #iel&e& #iel&e& &ierent alues for the !ass per%ent of )*) in an aspirin tablet, The titration sho"e& there "as an aera'e 5>9 !' of aspirin per tablet. "hi%h aera'e& about 5,< of the tablets !ass, sin' spe%trophoto!etr#. spe%trophoto!etr#. the "aelen'th use& to n& the absorban%e "as the "aelen'th of !ai!u! absorban%e for the &ilution "ith the 'reatest %on%entration. %on%entration. "hi%h "as <>7 n!, This !etho& sho"e& an aera'e of about 50 !' per tablet. resultin' resultin' in an aera'e aera'e !ass per%ent of 77,95, 77,95, The :a#er aspirin bran& that "e use& liste& that a sin'le tablet %ontains 5>< !' of )*) per tablet, ien that the !ass of an aspirin tablet "as al"a#s foun& to be bet"een 0,59 an& 0,40'. the epe%te& !ass per%ent of )*) "oul& ran'e fro! about 1-5, The alue of the titration "as !u%h %loser to the alue of "hat the tablets are a&ertise& to %ontain. an& "ere "ithin < of the bottle assa#, The results of the spe%trophoto!etr# "ere also "ithin the < assa#. but "ere not as %lose to the epe%te& alue, :oth titration an& spe%trophoto!etr# "ere !etho&s use& to &eter!ine the per%ent of )*) in a sin'le aspirin tablet. ea%h a&anta'eous for &ierent reasons, The titration inole& the use use of an in&i%ator in&i%ator an& 2a3H to to titrate the aspirin aspirin solution solution an& &eter!ine the olu!e of )*), 2a3H %ant be use& as a pri!ar# stan&ar& be%ause it is h#'ros%opi%. !eanin' that it attra%ts !oisture fro! the air an& %an
rea%t "ith %arbon &ioi&e. for!in' so&iu! %arbonate, Conseuentl#. the %on%entration %on%entration %annot be relie& upon as it !a# ar# oer ti!e if it is not %arefull# %ontaine&, 3ne a&anta'e of usin' a titration is that the buret an& %areful titratin' allo"s for a hi'h &e'ree of a%%ura%# an& pre%ision, This !etho& is also &isa&anta'eous be%ause "hen perfor!in' the titration. the rea%tion !a# not be instantaneous, instantaneous, t !a# be &iG%ult to &eter!ine the ea%t en& point. thus the ea%t olu!e, *pe%trophoto!etr# *pe%trophoto!etr# is an a&anta'eous !etho& be%ause it proi&es a ui% an& eas# anal#sis, Ho"eer. the a%%ura%# an& sensitiit# of the instru!ent !a# ar# base& on other fa%tors that !a# inIuen%e the absorption of a substan%e, hae !ore %on&en%e in the titration results be%ause there "as a !u%h s!aller &eiation in the !ass of aspirin in a sin'le tablet. sho"in' 'reater pre%ision, The lar'e aera'e &eiation &eiation fro! the spe%trop spe%trophoto!etr# hoto!etr# %oul& be &ue to the fa%t fa%t that the %on%entrations "ere &erie& fro! the stan&ar& %ure for ea%h in&ii&ual &ilution an& not throu'h an# &ire%t !easure, 3ne inherent error in the spe%trophoto!etr# pro%e&ure is that a sin'le tablet "as use& for ea%h of the &ilutions. an& onl# three tablets in total, This s!all sa!ple si$e in%reases in%reases the possibilit# of an issue one of the tablets se"in' the &ata. re'ar&less of the pre%ision of the eperi!ent itself, )n error inherent in both pro%e&ures pro%e&ures is the assu!ption that )*) rea%te& %o!pletel#, :# !ain' this assu!ption to &eter!ine the olu!e of )*) in the tablet. this %oul& result in the un&eresti!ation of its olu!e. thus &e%reasin' the nal aera'e !ass per%ent, ) uestion raise& b# the results is "hether or not the &ieren%es in alues %a!e fro! the use of &ierent !etho&olo'ies use& or if the# "ere &ue to natural ariation in the tablets of aspirin the!seles, :e%ause so fe" tablets "ere use& in this eperi!ent. eperi!ent. the inesti'ation inesti'ation
%oul& be taen further b# usin' a 'reater nu!ber of tablets for ea%h !etho& an& %o!parin' the alues obtaine& b# ea%h,
