Exp 4
Short Description
Download Exp 4...
Description
Astrero Astrero,, Fatima Fatima;; Marcos, Marcos, Junica; Junica; Marti Martin, n, King King Dave; Dave; Navar Navarro, ro, Diana Diana Rache Rachelle lle March 01, 2016 Chem 261 gh
Experiment # 4 DETERMINATION OF ASPIRIN BY INDIRECT TITRATION INTRODUCTION !n "irect titrations, a titrant o# stan"ar" concentration is "irectl$ a""e" to an anal$te anal$te o# un%no&n un%no&n concentra concentration tion '(arris, '(arris,2010 2010) ) !n"irec !n"irectt metho"s metho"s o# titratio titration n is carrie" out *$ a""ing a +uantit$ o# the ecess reagent to a s-eci.c reaction an" the unconsume" eces ecess s reagent is "etermine" via titration '(arris, 2010) /ac% titration is a -rocess -rocess &here an ecess ecess &hich is use" to consume an anal$te is "etermine" *$ titration &ith a secon" titrant !t is use#ul &hen its en"-oint is clearer than the en"-oint o# the "irect titration, or &hen an ecess o# the .rst reagent is re+uire" #or com-lete reaction &ith anal$te '(arris, 2010) Acet$l salic$lic aci" 'C (3), more commonl$ %no&n as as-irin, is one o# the most &i"el$ use" over4the4counter "rugs !t is o#ten ta%en to relieve -ain such as tootha toothache che,, hea"ac hea"ache he an" ma$ even even lo&er lo&er #ever #ever As its name name sugg suggest ests, s, acet$l acet$l salic$lic aci" is a miture o# t&o aci"s5acetic aci" an" salic$lic aci" &hich ma$ *e h$r"olie" *$ an al%ali to simultaneousl$ neutralie the t&o aci"s 7he &ea% aci" salts o# these aci"s at e+uivalence -oint &ill result to a -( &hich lies &ithin the range o# the in"icator &hich is -henol re", giving an evi"ent change in color #rom -in% to #aint $ello& 7he o*8ectives o# this e-eriment &ere to evaluate the -urit$ o# an as-irin sam-le, to -ractice -ro-er "ilution o# a solution an" the use o# a volumetric -i-ette an" to learn ho& to calculate an" evaluate results in a *ac% titration
MATERIALS AND METHODS !n the the -re-re-ar arat atio ion n an" an" stan stan"a "ar" r"i iat atio ion n o# 01 01 N (Cl (Cl solu soluti tion on,, 0 0 m9 ± 0.05 mL o# 12N concentrate" (Cl &as "ilute" in a 1004m9 volumetric :as% !n se-arate age 1 o# 10
RESULTS !n this e-eriment, the "etermination o# as-irin *$ in"irect titration &as "one 7he e-eriment &as "ivi"e" into t&o -arts; the -re-aration an" stan"ar"iation o# so"ium h$"roi"e 'Na() solution an" the anal$sis o# acet$lsalic$lic aci" 'A?A) or as-irin For the results, the ta*les #or the "i@erent "ata are sho&n *elo&
DATA A Prep!r!ti"n !n St!n!ri$!ti"n "% N!OH &"'(ti"n Normalit$ o# concentrate" (Cl olume o# (C9 use" to -re-are 01 N Normalit$ o# ?tan"ar" Na( olume o# (C9 titrate" 'B 00= ml) olume o# Na( use" 'B 00= ml) Normalit$ o# (Cl
12 N 20 m9 B 0000 m9 0100 N 7rial 1 2000 ml
7rial 2 2000 ml
7rial 2000ml
1=20 ml
1=30 m9
1=30 ml
002 N B 00003 N
001 N 001 N B B00003 N 00003 N Mean Normalit$ o# (Cl 00 B 00003 R?D 0= Table 1 ?tan"ar"iation o# Na( solution using (Cl For the ta*le 1, the normalit$ o# the concentrate" h$"rochloric aci" '(Cl) solution is 12 N 7he volume o# h$"rochloric '(Cl) aci" solution use" to -re-are 01 N so"ium h$"roi"e 'Na() is 00 ml &ith the uncertaint$ o# 00= ml &hile the normalit$ o# the stan"ar" so"ium h$"roi"e 'Na() solution &hich &as use" #rom the -revious e-eriment is 0100 N For the stan"ar"iation o# Na( solution, 2000 ml h$"rochloric '(Cl) aci" solution &as use" #or the three trials 7he volume o# so"ium h$"roi"e 'Na() solution ho&ever varie" #or the three trials 7he volume o# Na( use" #or the .rst trial is 1=20 ml &hile 1=30 ml Na( &as use" #or the secon" an" thir" trial 7he normalit$ o# (Cl &as com-ute" #or ever$ trial using this e+uationE N(Cl (Cl NNa( Na( 7he normalit$ o# (Cl com-ute" #or the .rst trial &as 002 N 7he normalit$ o# the secon" an" thir" trial &as the same &hich &as 001 N since the volume o# Na( >age ) o# 10
use" in stan"ar"iation &as also the same 7he mean normalit$ o# (Cl #or the three trials &as 00 N &hile the relative stan"ar" "eviation &as 0= For the calculations o# these results, the solutions are sho&n *elo& olume o# (Cl Gse" to >re-are 0 1 N (Cl N NaOH x V NaOH 0 ; 1 N x 0.250 L V HCl = 20 ml 12 N N HCl Gncertaint$ o# the olume o# (Cl Gse" to >re-are 01N (Cl
√( = ( √ )
combineduncertainties = computed vol
uncertainty of vol . flask volume
combineduncertainties 2.08 ml HCl
0.10
(√( ) ) 0.10
cu
)
2
2
250
2
250
20 ml
cu 20 B 0000 ml Normalit$ o# ?tan"ar" Na( 7rial 1 N(Cl (Cl NNa( Na( N(Cl 002000 9 0100 N 001=20 9 N(Cl
−3 1.5656 x 10
0.02000
N(Cl 002 N N(Cl (Cl NNa( Na( N(Cl 002000 9 0100 N 001=30 9
7rial 2
−3
N(Cl
1.5862 x 10 0.02000
N(Cl 001 N N(Cl (Cl NNa( Na( N(Cl 002000 9 0100 N 001=30 9
7rial
−3
N(Cl
1.5862 x 10 0.02000
N(Cl 001 N Gncertainties in the Normalit$ o# (Cl 7rial 1
c.u. = computed N
√(
)(
)(
2 2 meanunc.of N NaOH unc .of burette + unc.of pipette + vol volume mean N NaOH
7rial 1
>age * o# 10
)
2
c.u. = computed N c.u.
√(
√( ) +( (√( ) +( ) +(
0.07828
=
0.05
cu
2
15.20
0.05
)(
)( ) +( )
2 2 meanunc.of N NaOH unc .of burette unc.of pipette + + vol volume mean N NaOH
0.07
50.00
2
0.07
15.20
2
2
50.00
0.0004
)
2
2
0.1030
0.0004 0.1030
)) 2
002
cu 002 B 00003 N 7rial 2
c.u. = computed N
c.u.
√(
√( ) +( (√( ) +( ) +(
0.07828
=
0.05
cu
2
15.40
0.05
)(
)( ) +( )
2 2 meanunc.of N NaOH unc .of burette unc.of pipette + + vol volume mean N NaOH
0.07
50.00
2
0.07
15.40
2
2
50.00
0.0004
)
2
2
0.1030
0.0004 0.1030
)) 2
001
cu 001 B 00003 N 7rial
c.u. = computed N c.u.
√(
√( ) +( (√( ) +( ) +(
0.07828
=
0.05
15.40
0.05
cu
)(
)( ) +( )
2 2 meanunc.of N NaOH unc .of burette unc.of pipette + + vol volume mean N NaOH
2
15.40
2
0.07
50.00
0.07
2
50.00
2
0.0004
)
2
2
0.1030
0.0004 0.1030
)) 2
001
cu 001 B 00003 N Mean Gncertaint$ in the Normalities o# (Cl ( 0.07828 ± 0.0004 )+ ( 0.07931 ± 0.0004 ) + ( 0.07931 ± 0.0004 ) Mean 0 B 00003 3 N Mean o# (Cl
Normalit$
x´ x´
Σ x
i
n 0.07828 + 0.07931 + 0.07931 3
>age 4 o# 10
x´ =
0.2369 3
x´ 00 N Relative ?tan"ar" Deviation
?tan"ar" Deviation s
√
2
Σ ( x i−´ x ) n−1
s
√
2
2
( 0.07828 – 0 07897 ) + ( 0.07931 – 0 07897 ) + ( 0.07931 – 0 07897 )
s
s
s s
2
3− 1
√ ( √ √
(−6.9 x 10− ) +( 3.4 x 10− ) +( 3.4 x 10− ) 4 2
4 2
4 2
2 −7 4.761 x 10
)+( 1.156 x 10− )+( 1.156 x 10− ) 7
7
2
−7 7.073 x 10
2
√ 3.5365 x 10−
7
s =36 10 H3 s R?D x´ x 100
−4 5.9468 x 10
0.07897
100
'=0= 10 H) 100 0=0= or 0= Table 2 Calculations on the >re-aration an" ?tan"ar"iation o# Na( ?olution
B An!'+&i& "% S!mp'e Mass o# A?A sam-le 'B 00001 g) 006 g 7rial 1 7rial 2 7rial olume ali+uot ' B 00 =000 ml =000ml =000 ml ml) olume o# (Cl use" ' B 1130 ml 1120 ml 1120 ml 00= ml) Mass A?A in sam-le 00=3 g B 006=== g B 006=== g B 'grams) 0000= g 0000= g 0000= g A?A =3 6=== 6=== Mean mass A?A 0061 B 0000= g R?D 6=1 Mean A?A 61 Table 3 Calculate" Results on Anal$sis o# Acet$lsalic$lic Aci" 'A?A)
>age , o# 10
For the -art o# anal$sis o# sam-le, 006 g o# as-irin &as &eighe" =000 ml o# volume ali+uot &as measure" #or ever$ trial For the .rst titration, 1130 ml o# (Cl &as use" &hile #or the secon" an" thir" titration, the volume o# h$"rochloric aci" '(Cl) use" &as 1120 ml !n the .rst trial, 00=3 g o# as-irin &as use" in the 1130 ml o# (Cl solution &hile same mass o# as-irin &hich &as 006=== g &as use" in the same volume also o# the 1120 ml (Cl solution 7he mean mass &as com-ute" &hich &as 0061 &ith 0000= g uncertaint$ 7he relative stan"ar" "eviation &as 6=1 7he -ercent mass &as also com-ute" =3 #or the .rst trial an" 6=== #or secon" an" thir" trial 7he -ercent mass o# as-irin &as 61 &hich means it has im-urities For the sam-le calculations regar"ing anal$sis o# sam-le, the solutions are ta*ulate" *elo& Mass o# A?A in sam-le 'grams)
[
(
[
( 0.1030 N NaOH x 50.00 ml NaOH )−
!"! = ( N NaOH x V NaOH ) − N HCl x V HCl x 7rial 1
!"! =
)]
vol.stock x $% !"! vol . ali#uot
(
0.07897 N HCl x 11.40 ml HCl x
(
0.07897 N HCl x 11.20 ml HCl x
(
0.07897 N HCl x 11.20 ml HCl x
250 ml 50 ml
g A?A =3 mg 00=3 g 7rial 2
!"! =
[
( 0.1030 N NaOH x 50.00 ml NaOH )−
250 ml 50 ml
g A?A 6=== mg 006=== g 7rial
!"! =
[
( 0.1030 N NaOH x 50.00 ml NaOH )−
250 ml 50 ml
)]
x
)]
x
)]
x
180.159 2 me#
180.159 2 me#
180.159 2 me#
g A?A 6=== mg 006=== g Gncertainties in the mass o# A?A in sam-le
c.u. = computedmass
√(
meanunc.of N NaOH meanN NaOH
)( 2
)(
)(
2 meanunc .of N HCl 2 unc . of burett unc.of pipette + + + volume mean N HCl volume
7rial 1
c.u. = 0.05843 !"! c . u .=
(√(
√(
0.1030 N NaOH
0.0004 N
0.1030 N
0.0004 N
) +( 2
NaOH
) +( 2
0.07 50.00 ml
) +( 2
0.07 50.00 ml
) +( 2
0.07897 N
0.0004 N 0.07897 N
cu 00=3 B0000= g 7rial 2
>age - o# 10
HCl
) +( 2
HCl
) +( 2
0.0004 N
0.05
11.40 ml HCl
0.05
11.40 ml HCl
))
)
2
2
x 0.05843 !"!
c.u. = 0.06555 !"! c . u .=
(√(
√(
0.1030 N NaOH
0.0004 N
0.1030 N
) +( 2
) +( 2
0.0004 N
50.00 ml
) +( 2
0.07
NaOH
0.07
50.00 ml
) +( 2
0.07897 N
0.0004 N 0.07897 N
HCl
) +( 2
HCl
) +( 2
0.0004 N
)
2
0.05
11.20 ml HCl
)) 2
0.05
11.20 ml HCl
x 0.06555 !"!
cu 006=== B0000= g 7rial
c.u. = 0.06555 !"! c . u .=
(√(
√(
0.1030 N NaOH
0.0004 N
0.1030 N
) +( 2
) +( 2
0.0004 N
50.00 ml
) +( 2
0.07
NaOH
0.07
50.00 ml
) +( 2
0.07897 N
0.0004 N 0.07897 N
HCl
) +( 2
HCl
) +( 2
0.0004 N
11.20 ml HCl
)) 2
0.05
11.20 ml HCl
cu 006=== B0000= g Mean Gncertaint$ o# the Mass o# A?A in ?am-le ( 0.05843 ± 0.0005 ) + ( 0.06555 ± 0.0005 ) + ( 0.06555 ± 0.0005 ) Mean 3
x 0.06555 !"!
0000= g Relative ?tan"ar" Deviation o# A?A Mass " x 100 R?D & ´
R?D
√
2
2
A?A
!"! A?A
0.1
x 100
7rial 1E
!"! A?A
0.1
x 100
0.05843 0.1
x 100 =3
7rial 2E
!"! A?A
0.1
x 100
0.06555 0.1
x 100 6===
7rial E
!"! A?A
2
(0.05843 −0.06318 ) +( 0.06555 −0.06318 ) +( 0.06555− 0.06318) 3− 1 x 100 ´ 0.06318
R?D 6=1
0.1
x 100
0.06555 0.1
x 100 6===
>age . o# 10
)
2
0.05
0061
B
Mean A?A 58.43
Mean
+ 65.55 + 65.55 3
=63.18
Table 4 Calculations n Anal$sis o# Acet$lsalic$lic Aci"
DISCUSSION As-irin, a "rug &i"el$ %no&n #or its analgesic, anti-$retic, an" anti4 in:ammator$ -ro-erties, is a com-oun" "erive" #rom t&o aci"s namel$ acetic aci" an" salic$lic aci" 7his e-eriment, sought to +uantitativel$ "etermine the amount o# acet$lsalic$lic aci" in as-irin 'A?A) *$ *ac%4titration to anal$e the -urit$ o# as-irin an" to a--l$ the conce-t or *ac%4titration in the "etermination o# its -urit$ 7his activit$ consiste" o# t&o -arts First is the -re-aration an" stan"ar"iation o# 01N so"ium h$"roi"e 'Na() solution an" the anal$sis o# as-irin Man$ car*o$lic aci"s in this case, as-irin is not suIcientl$ solu*le in &ater to -er#orm "irect titration in a+ueous solution 7he aci" can *e titrate" &ith a+ueous *ase &hen this -ro*lem eists Alternativel$, the aci" can *e "issolve" in an ecess o# stan"ar" *ase #ollo&e" *$ *ac%4titration &ith stan"ar" aci" &hich &as h$"rochloric aci" in this case /ut *e#ore using so"ium h$"roi"e 'Na() to titrate As-irin, it must *e stan"ar"ie" .rst in or"er to get %no&le"ge o# its accurate concentration hili- Allan G-"ates (arris, DC '2010) Luantitative Chemical Anal$sis 'th e") Ne& Oor%E ( Freeman P Co ?%oog, D, est, D, (oller, F, an" Crouch ? '2013) Fun"amentals o# Anal$tical Chemistr$, th e" /elmont, CAE /roo%sCole, Cencage 9earning ?ta-el,
View more...
Comments
