DETERMINATION OF CITRIC ACID IN FRUIT JUICE RYAN JACOB C. AGDON MARY JESRETH V. BAYAS DE LA SALLE UNIVERSITY- DASMARIÑAS DASMARIÑAS CITY, CAVITE, PHILIPPINES
ABSTRACT Titration is a common process in chemistry used to determine the concentration of a substance present in a solution. It often used in determining concentration in an acid-base solutions. In this experiment, the process of titration is used to determine the exact molarity of the sodium hydroxide solution as it is mixed with sets of tests- KHP and determining the concentration of citric acid present in fruit juices. Phenolphthalein is used as an indicator to determine the end point of the experiment experiment thus the concentration concentration of a!H and citric acid is determined. determined. The resulting molarity of a!H fron KHP titration process is "."#$% and ".#&%. In determing the concentration, in terms of molarity, of citric acid present in 'est-! pinapple fruit juice, the (" m) unfiltered and the filtered juices results results to "."*" "."*" % and "."&$% respecti+ely respecti+ely..
INTRODUCTION In determining the concentration of a solution, a standard is used to compare its uantitati+e +alue. The process of titration is one of the commonly used processes in determining the unnown uantity of a sample from compared standard. odium hydroxide, as a base, was standardi/ed to determine the concentration of acid present in a solution. 0&1 2hen acids and bases react with one another, it results to the formation of salt and water. It is a balanced chemical reaction thus will result to a neutral state. In titration method, the standardi/ed solution is slowly added to the solution using a calibrated calibrated burette. 3dding 3dding the sample will result to being more acidic or basic depending which is added to the excess solution. ince the formation of salt and water will determine if the experiment reach its end point. 3n indicator will be used as it differentiates the color of the solution to readily obser+e if the end point is reached. The final +olume of the solution inside the burette will be indicated endpoint of the experiment. 0*1 In order order to exact exactly ly stand standard ardi/e i/ed d the prepa prepared red a!H a!H solut solution ion,, sets sets of soluti solution on is used used to stand standard ardi/e i/e it. The The stand standard ardi/a i/atio tion n test test are using using the the KHP KHP solut solution ion and and deter determin minin ing g the concentration of citric acid present in fruit juices.
MATERIALS AND METHODS To start the titration process, a standardi/ed a!H is prepared with a &." g a!H in solid form dissol+ed in *(" m) water. 4alculating its molarity, the solution is in a ".& % a!H. ( m) standard standardi/ed i/ed a!H is used to rice the calibrat calibrated ed burette. burette. The remainin remaining g solution solutions s filled filled the apparatus with its +olume noted as the initial +olume of the experiment. In the KHP test, "."( g KHP, KHP, in solid form, is dissol+ed in (" m) water. ( drops of phenolphthalein phenolphthalein is used as an indicator of the endpoint. The a!H is slowly titrated in the KHP solution until it shows a relati+e pin color
as it reached its endpoint. 5olume of the burette was noted to measure the +olume of a!H used. 6or the determination of citric acid present in fruit juices, two sets (" m) fruit juice sample is prepared. !ne is in its original color while the other is filtered. The same procedure is used with the a!H solution and the phenolphthalein indicator. The +olume of the a!H solution was is used to calculate the concentration of citric acid present in the sample fruit juice. The results were calculated and interpreted. 0$1
RESULTS AND DISCUSSIONS A. Preparat!" !# NaOH %ass of ".& % a!H 5olume of solution %oles of a!H
".#7 g *(" m) 8" g9mol
To prepare a ".& % a!H standardi/ed solution for the titration experiment, the mass of a!H should be determined first for the gi+en amount of sol+ent to produce an accurate ".& % a!H solution. %olarity : moles of solute 9 5olume of olution 0)1 %oles : 0%olarity105olume of olution in liters1 %oles of olute : 0".& % a!H10".*( )1 : $.$%& '!(e) NaOH 4on+erting the number of moles to mass in grams will determine the mass of a!H needed for the experiment. It is based on the molecular weight of a!H which is $#.## g9mol
g NaOH 1 mole NaOH
39.99
"."*( moles a!H x
: ".## g ; * + NaOH
To produce ".& % *(" m) solution, & g a!H should be dissol+ed in *(" m) water to produce a standardi/ed a!H solution.
B. Ttrat!" !# HP %ass of KHP %olecular %ass of KHP %oles of KHP Initial burette reading 6inal burette reading 5olume of a!H used %olarity of a!H 3+e. %olarity of a!H = error
"."(& g *"8.* g9mol *.(" x&" -8 moles (." m) <.< m) *.< m) "."#$ % "."#* % ".#* =
"."(* g *"8.* g9mol *.(( x&" -8 moles <.< m) &".( m) *.7 m) "."#& %
TITRATION OF HP 6or the first part of the experiment, the process of titration is used to determine the molarity of a!H from potassium hydrogen phthalate 0KHP1 . This organic substance is solid, weighed with an a+erage amount of "."( g and dissol+ed in (" m) water. 081
HP NaOH
NaP H%O
It is obser+ed that & mole KHP is used to completely react with & mole a!H. >sing basic stoichiometry, the molarity of a!H is easily determined. 4alculations? @i+en? %ass of KHP A "."(& g 0&1 "."(* g 0*1
Belationship? & mole a!H : & mole KHP
%olecular massof KHP A *"8.8 g9mol Trial &? "."(& g
Trial *? "."(& g 1 mole KHP
"."(& g KHP x
204.2 g KHP
1 mole KHP
:
"."(* g KHP x
%.&$ *$ -/ '!(e) HP
204.2
g KHP :
%.&& *$ -/ '!(e) HP
ince the number of moles of KHP is eui+alent to the number of moles of a!H, thus the calculated +alue of KHP moles will also be the a!H moles. 6ollowing the formula of determining molarity of a solution, the following calculations were made. Trial &?
Trial *?
%oles of a!H : *.(" x&" -8 moles 5olume of a!H used : *.< x&" -$ )
%oles of a!H : *.(( x&" -8 moles 5olume of a!H used : *.7 x&" -$ )
%olarity : %oles of olute 9 5olume of olution 0)1
%olarity : %oles of olute 9 5olume of olution 0)1
%: *.(" x&" -8 moles a!H 9 *.< x&"
%: *.(( x&" -8 moles a!H 9 *.7 x&"
: $.$01 M
-$
)
-$
)
: $.$0* M
6rom the a+erage molarity of "."#* % a!H and the prepared ".& % a!H solution, there is a minute ".#* = error in the experiment. Thus the +alue of the molarity of the a!H after being standardi/ed is determined and compared.
C. ANALYSIS OF CITRIC ACID OF 2EST-O PINEAPPLE FRUIT JUICE V!(4'e !# J45e M!(e54(ar Ma)) !# Ctr5 A53 M!(e) !# 5tr5 A53 I"ta( 94rette rea3"+ F"a( 94rette rea3"+ V!(4'e !# NaOH 4)e3 M!(art: !# Ctr5 A53 C!"5e"trat!" !# Ctr5 a53 ;" * 'L< C!"5e"trat!" !# 5tr5 a53 ;" &$ 'L #r4t >45e<
U"#(tere3 Fr4t J45e &$.$ 'L *0%.*% +6'!( 0.*1 *$-/ '!(e &.$ 'L 1%./ 'L %8./ 'L $.$%$ M
F(tere3 Fr4t J45e &$.$ 'L *0%.$*% +6'!( -/ 6.78 *$ '!(e) &.$ 'L %&.$ 'L %$.$ 'L $.$*1 M
$.*8& +6'L
$.*%= +6'L
=.88 +6 &$ 'L
7./$ +6 &$ 'L
4itric acid is a common naturally occurring organic acid. It is a wea acid and +ery soluble thus it is easily processed as additi+es that enhance fla+ors especially on fruit drins. 0(1. 4itirc acid is the one responsible for the sour taste present in our fruit drins thus it has a certain amount in order to complement with the fruitCs fla+or. In this experiment, titration process is used to determine the concentration of citric acid present in 'est-! Pineapple 6ruit Duice using a!H olution. The following chemical reaction occurs when 4itric acid present in fruit juice is titrated with a!H solution. 4$H(04!!H1$ 0a1 E $ !H-
0a1
4$H(04!!1$$ 0a1 E H*! 0l1
4itric acid has $ carboxylic acid groups and is capable of reacting with the hydrogen ion present in a!H. alt and water is formed by the neutrali/ation of sodium hydroxide, which is a base, mixed with it. 0$1. In the titration process of 'est-! pineapple fruit juice with a!H solution 0with a nown molarity1, the change in color and the amount used in titrating the fruit juice will indicate the concentration of acid present in the fruit juice. 0F1
4alculation? 4itric acid 3nalysis 6ormula? %oles : 0molarity1 0+olume of solution in )1 %olarity : moles of solute9 liter solution = composition : mass of solute9 +olume of solution Trial &? %oles of a!H
Trial *? %oles of a!H
5olume of a!H used : *<.8 m) %olarity of a!H : ".& %
*.<8 x&" -$ )
5olume of a!H used : *"." m) %olarity of a!H : ".& %
*."" x&" -$ )
%oles of a!H: 0".& %1 0*.<8 x&" -$ )1
%oles of a!H: 0".& %1 0*.""x&" -$ )1
: %.8/ *$-1 '!(e) NaOH
: %.$$*$-1 '!(e) NaOH
>sing the moles of a!H calculated from the +olume of a!H used, calculating the number of moles of citric acid will be based on the moles of a!H and its relationship with the citric acid. 4$H(04!!H1$ 0a1 E $ !H-
0a1
4$H(04!!1$$ 0a1 E H*! 0l1
Belationship? & mole 4itric 3cid ? $ moles a!H Trial &? %oles of 4itric acid
Trial *? %oles of 4itric acid
%oles of a!H : *.<8 x&" -$ moles a!H
%oles of a!H: *.""x&" -$ moles a!H
1 moleCitric acid
*.<8 x&"-$ moles a!H x
3 moles NaOH
M!(e) !# 5tr5 a53 ? 0.*1 *$ -/ '!(e)
1 moleCitric acid
*."" x&" -$ moles a!H x
3 moles NaOH
M!(e) !# 5tr5 a53 ? 7.78 *$ -/ '!(e)
Getermining the amount of citric acid in grams present in the fruit juices will be based on the number of moles and the molecular weight of citric acid. 4itric acid molar mass? *0%.*% +6'!(
Trial &? %ass of 4itric acid
Trial *? %ass of 4itric 3cid
%oles of citric acid : #.&$ x&" -8 moles
%oles of citric acid : F.F< x&" -8 moles
192 . 12 g citricacid -8
#.&$ x&" moles citric acid x
1 mole citricacid
: ".&<( g citric acid per m)
192 . 12 g citric acid
F.F< x&"
-8
moles x
1 mole citricacid
: ".&*7 g citric acid per m)
The calculated mass of citric acid is present in a & m) fruit juice. In the experiment, (" m) of fruit juice is used. To determine the +alue citric acid present in (" m) fruit juice processed, simply multiplying the mass of citric acid will determine its uatity present in the indicated +olume of fruit juice. Trial &? %ass of 4itric acid in (" m) fruit juice
Trial *? %ass of 4itric 3cid in (" m) fruit juice
%ass of citric acid : ".&<( g citric acid per m)
%ass of citric acid: ".&*7 g citric acid per m)
"."&<( g x (" m) : 7.<< g citric acid per (" m) fruit "."&*7 g x (" m) : F.8 g citric acid per (" m) fruit juice juice
In terms of molarity, the moles of citric acid will determine its molar concentration present in (" m) sample of 'est-! fruit pineapple juice. Trial &? %oles of 4itric acid : #.&$ x&" -8 moles 5olume of 6ruit juice 0)1 : "."( )
Trial *? %oles of 4itric acid : F.F< x&" -8 moles 5olume of 6ruit juice 0)1 : "."( )
%olarity : moles of solute9 ) solution
%olarity : moles of solute9 ) solution
% : #.&$ x&" -8 moles 9 "."( ) : $.$% M
% : F.F< x&" -8 moles 9 "."( ) : $.$*1 M
The molarity of the unfiltered and filtered 'est A! pineapple fruit drin is "."* % and "."&$ % respecti+ely. Their a+erage molarity is "."*< %. The difference from the two samples, e+en if they are from the same brand and amount is due to the indication of color. The unfiltered pineapple fruit drin has higher uantitati+e +alues than the filtered sample because it is harder to see the discoloration indicated by the phenolphthalein due to its color. >nlie the filtered one, it is easier to obser+e the discoloration. This factor is one of the pointers to be considered in doing the experiment in order to produce consistent +alues.
Re#ere"5e)@ %offett, T.%. Dr., Pater, . Getermination of 4itric 3cid in 6ruit Duice. cited "( Danuary *"&FJ 3+ailable at http?99faculty.plattsburgh.edu9tom.moffett9che&&&9titrationlab.pdf
0&1 0*1 081 xperiment &8? tandardi/ation of odium Hydroxide olution. cited &# Danuary *"&FJ 3+ailable at http?99chemtech.org9cn9cn&&"(9experiments9standardi/ationa!H.pdf 0$1 The ui+alent 2eight of an 3cid. Part &? tandardi/ation of a!H. cited &# Danuary *"&FJ 3+ailable at http?99faculty.uml.edu9jameshall978&*89*"pt&.htm 0(1 4omparison of 3cidity in 6ruit Duices. Institute of 4hemistry, >P)L, 4ollege, )aguna. *"&* cited &# Danuary *"&FJ Betrie+ed from http?99www.slideshare.net9adusmmangao9comparison-of-the-acidity-of-fruit-juices-&(#7"*(F 0F1 Total 3cidity on a mall cale.6linn cientific Inc. *""#. cited *" Danuary *"&FJ Betrie+ed from https?99www.flinnsci.com9media9F*"F7$9#&*F$.pdf
4hang, B.D. @eneral 4hemistry? The ssential 4oncepts. F th ed. ew Mor. The %c@raw-Hill 4ompanies. Inc. *"&*
