atq experiment 8 chem 26.1

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J.N. Macabata / Chemistry 26.1 (2016) P a g e | 1

Quantitative eterminati!n !" iss!#ve$ %&ygen C!ntent by 'in#er e$!& *itrati!n Je#ica N. Macabata

aNational Institute of Geological Sciences. University of the Philippines- Diliman, 1101, ue!on "ity

Per"!rme$ +0 June 2016, -ubmitte$ Ju#y 2016

- * C *iss!#ve$ !&ygen




Introduction

n stu$ying envir!nmenta# an$ marine scienceit is im3!rtant t! have n!4#e$ge !n $iss!#ve$!&ygen (%2) c!ntent !" a "resh4ater sam3#e.iss!#ve$ !&ygen c!ncentrati!n is e&3resse$ asthe number !" mi##i#itres !" !&ygen gas (%2) 3er

#itre !" "resh4ater sam3#e (m5 !r 51). 'ater3!##uti!n c!ntr!# an$ 4aste 4ater treatment3r!cess c!ntr!# are $etermine$ by the $iss!#ve!&ygen test2. t may be use$ by marine bi!#!gistt! measure 3rimary 3r!$ucti!n !r by 3hysica#!cean!gra3hers t! stu$y 4ater masses in the!cean. n terms !" chemistry it 3r!vi$es measure!" the re$!& 3!tentia# !" a 4ater c!#umn. 'in#er meth!$ $eve#!3e$ in 1777 is use$ t!accurate#y measure the $iss!#ve$ !&ygenc!ncentrati!n !" a 3articu#ar sam3#e. *he meth!$4as then m!$i8e$ by -tric#an$ an$ Pars!ns in1967. *his e&3eriment 3r!vi$es the rea$ers then!4#e$ge t! 3er"!rm the 4ater sam3#ing an$3retreatment techni:ues "!r $iss!#ve$ !&ygenana#ysis. t 4i## a#s! $etermine the am!unt !" $iss!#ve$ !&ygen in a 4ater sam3#e "r!m a 3!n$in the nstitute !" Mathematics C!##ege !" -cience;niversity !" the Phi#i33inesi#iman using'in#er re$!& titrati!n an$ $iscuss the chemistrybehin$ the 'in#er meth!$ "!r $iss!#ve$ !&ygen$eterminati!n.

Materials and Methods

n 3er"!rming the e&3eriment ir!n stan$sburette c#am3s an$ a#uminium "!i# are nee$e$.'e a#s! 3re3are$ c#ean g#ass b!tt#e 4ith ca3burettes (<0 m5) beaers (<0 100m5)v!#umetric =ass (2< 100 2<0m5) v!#umetric3i3ettes (10 <0m5) >r#enmeyer =ass (2<0m#)4atch g#ass an$ syringe. 'e a#s! use$ ana#ytica#ba#ance t!3#!a$ing ba#ance an$ h!t 3#ate "!r thee&3eriment. *he "!##!4ing s!#uti!ns sh!u#$ a#s! be3re3are$?1. 2<.0 m5 .0 M Mn-% "r!m Mn-%@2A2%crysta#s B 4eigh

17.62 grams !" the crysta#s an$ $iss!#ve inab!ut

10m# $isti##e$ 4ater then 8#ter thes!#uti!n int! a

2<m# v!#umetric =as an$ $i#ute t! mar.2. 2<.0 m5 17 M Na%A 4ith <.0 g an$ 0.1< gNaN+ B

4eigh the "!##!4ing s!#i$s an$ $iss!#ve in abeaer

4ith 10 m5 $isti##e$ 4ater 4hi#e stirring ina h!t

3#ate then trans"er t! a 2<m5 v!#umetric=as an$ $i#ute t! mar. *his must be

$!ne in a 4ater bath un$er the "umeh!!$.

+. 2<0.0 m5 0.12< M st!c Na2-2%+ s!#uti!n "r!mNa2-2%+@<A2% crysta#s B 4eigh g !" crysta#s in abeaer an$

$iss!#ve in ab!ut 100.0 m5 b!i#e$ $isti##e$4ater

then trans"er t! a 2<0m5 v!#umetric =as.'ash

the beaer 4ith b!i#e$ $isti##e$ 4ater an$catch

the 4ashings int! the =as.. <0.0 m5 0.< M A2-% s!#uti!n<. -tarch s!#uti!n B 4eigh 1.0 g !" starch in abeaer an$

$iss!#ve unti# a sm!!th 3aste is !btaine$.P!ur it

in a 100.0 m# b!i#e$ $isti##e$ 4ater an$ee3 the

s!#uti!n in 90100 $egrees Ce#sius t! av!i$$rying u3.

6. 2<0.0 m5 0.012< M stan$ar$ Na 2-2%+ s!#uti!n

"r!m the0.12< M st!c Na2-2%+ s!#uti!n B 3i3ette

0.12< Mst!c s!#uti!n an$ trans"er t! a 2<0.0 m# v!#umetric =as an$ $i#ute t! mar.

-tan$ar$iDati!n !" the titrant Na2-2%+ 4as$!ne by 4eighing 0.1< grams !" the 3rimarystan$ar$ %+ an$ $iss!#ve$ in <0.0 m5 !" $isti##e$4ater. *hen the s!#uti!n 4as trans"erre$:uantitative#y int! a 100m5 v!#umetric =as an$$i#ute$ t! mar. *hree 10m5 a#i:u!ts 4as taen"r!m the s!#uti!n an$ trans"erre$ int! three 2<0m5 >r#enmeyer =ass. 20.0 m# !" 4ater 1.0g !" an$ 10.0 m5 !" 0.< M A2-% 4as a#s! a$$e$ t!each !" the s!#uti!n in the =as an$ imme$iate#ytitrate$ 4ith the stan$ar$ Na2-2%+. 'hen the 3a#eye##!4 s!#uti!n is !btaine$ 4e a$$e$ 1 m5 !r 20$r!3s !" starch s!#uti!n that causes it t! turn t!b#ue. mme$iate#y titrate it again unti# the b#uec!#!ur $isa33ears. ec!r$ the initia# an$ 8na#s!#uti!n !" the titrant in each sam3#e s!#uti!n. E!r the 4ater ana#ysis sam3#e 4e 4ent t! thenstitute !" Mathematics "r!nt yar$ an$ 8##e$ theem3ty g#ass b!tt#e c!vere$ 4ith a#uminium "!i# t!!ver=!4ing 4ith the 3!n$ 4ater. 'e c!vere$ the

m!uth !" the g#ass b!tt#e 4ith its airtight ca34hi#e it is sti## submerge$ in the 4ater t! av!i$the inc#usi!n !" air bubb#es. "ter getting thesam3#e 4e a$$e$ the "!##!4ing reagents insuccessi!n? 0.< m5 !" Mn-% an$ 0.< m5 !" Na%A4ith an$ NaN+ s!#uti!n. *hen c#!se the b!tt#ean$ shae it th!r!ugh#y. em!ve the c!ver againan$ s#!4#y a$$ 2.0 m5 !" c!ncentrate$ A +P%. ##the a$$iti!n !" reagents 3er"!rme$ 4as $!nebe#!4 the sur"ace !" the 4ater using measuring3i3ettes t! av!i$ inc#usi!n !" air bubb#es. C!ver an$ shae the b!tt#e an$ #et it stan$ "!r10 minutes as instructe$. *hen tae a <0.0 m5

a#i:u!t !" the s!#uti!n an$ trans"er int! a 2<0m5>r#enmeyer =as. *itrate it 4ith the stan$ar$Na2-2%+ s!#uti!n unti# a 3a#e ye##!4 c!#!ur is!btaine$ then a$$ 1.0 m# !r 20 $r!3s !" starch



J.N. Macabata / Chemistry 26.1 (2016) P a g e | +

s!#uti!n. *he 3a#e ye##!4 s!#uti!n 4i## turn int!b#ue then c!ntinue titrating unti# the b#ue c!#!ur$isa33ears. ec!r$ the initia# an$ 8na# v!#ume !" the titrant in each sam3#e s!#uti!n.

Results and Discussion

*he stan$ar$iDati!n !" Na2-2%+ inc#u$es the"!##!4ing e:uati!ns?

2 F G + H1I2-2%+

2 F + G -%6

2 F + H2I *he st!ichi!metric rati! is 1mm!# %+

? 6mm!#s -2%+

2. A2-% is a$$e$ t! increase theaci$ity !" the s!#uti!n an$ 4i## #et the reacti!n4ith i!$ate H%+

I t! tae 3#ace. !$ine is ac!mm!n !&i$iDing titrant. C!m3are$ 4ith !therre$!& titrants #ie Mn% Ce F an$ Cr2% i!$ine isa 4ea !&i$iDing agent an$ is !n#y use"u# inana#ysis !" ana#ytes that are str!ng re$ucingagents1. ecause !" i!$ineKs 3!!r s!#ubi#ity

s!#uti!ns are 3re3are$ by a$$ing an e&cess!" . ci$ic A2-% 4as a$$e$ 8rst t! a$Lust theenvir!nment !" the s!#uti!n an$ increase theaci$ity then 4as a$$e$ t! 3r!vi$e the nee$e$t! increase the s!#ubi#ity !" 2 an$ "!rm a m!res!#ub#e trii!$i$e i!n +

. -ince $irect titrati!n c!u#$nKt be 3er"!rme$ t! s!#uti!ns because it is subLecte$ t! air !&i$ati!n4hen "!rming + "r!m e&cess is a$$e$ t!re$uce the ana#yte an$ #iberate a st!ichi!metricam!unt !" +. n 4ater sam3#e ana#ysis the "!##!4inge:uati!ns are inv!#ve$?

Mn-%@2A2% G Mn2F F -%2 H+I

Mn2F F 2%A G Mn(%A)2 HI%2 F Mn(%A)2 F 2A2% Mn(%A)+(s) H<I %%2 F Mn(%A)2 Mn%(%A)(-) F 2A2% H6I

*he st!ichi!metric rati! is 1 mm!# %2? mm!#s-2%+

2. *he sam3#e s!#uti!n t! be ana#yse$ istreate$ 4ith a s!#uti!n !" Mn-% an$ then 4ith as!#uti!n !" Na%A an$ as sh!4n in reacti!ns +an$ . ;n$er these a#a#ine c!n$iti!ns $iss!#ve$!&ygen (%2) !&i$iDes the Mn2F t! Mn%2. *henc!ncentrate$ 3h!s3h!ric aci$ (A+P%) 4as a$$e$t! the sam3#e. ;n$er the ne4 c!n$iti!ns is

!&i$iDe$ t! +

by Mn%2.Mn-% 4as a$$e$ 8rst t! the s!#uti!n in !r$ert! have a stea$y s!urce !" Mn2F i!ns nee$e$ "!rthe reacti!n t! !ccur. *hen 0.< m# !" Na%A 4ith an$ NaN+ s!#uti!n 4as a$$e$ an$ t!getherthey "!rm amm!nium hy$r!gen carb!nate(NAAC%+) an$ s!$ium aDi$e (NaN+). NAAC%+ isa$$e$ t! 3revent the inter"erence !" !rganicc!m3!un$s in the s!#uti!n 4hi#e NaN+ 4asintr!$uce$ t! e#iminate the inter"erence !" nitrite(N%2) in the s!#uti!n. %ther than thi!su#"atenitrite is a#s! !&i$iDe$ by i!$ine that resu#ts t! there$ucti!n !" the v!#ume !" the titrant use$. t this

3!int 3reci3itates 4ere "!rme$ as state$ inreacti!ns < an$ 6. Ph!s3h!ric aci$ 4as a#s! a$$e$ t! the s!#uti!nt! have an aci$ic envir!nment "!r the reacti!n

an$ $iss!#ves the 3reci3itates "!rme$ ear#ier. ta#s! inactivates Ee+F i!ns that may inter"ere an$c!nsume the !&ygen in the sam3#e. *he s!#uti!nn!4 has a 3A va#ue ranging "r!m 1 t! 2.< a"terthe a$$iti!n !" the aci$. *he a$$iti!n !" everyreagent is in a $e8nite se:uence because everya$$e$ chemica# reacts "!r the c!m3#eti!n !" the

reacti!n !r e#iminati!n !" inter"ering substances.an$!m a$$iti!n !" the reagents may causeerr!rs in resu#ts !r the reacti!n may n!t 3r!cee$.

*he am!unt !" + "!rme$ is $etermine$ by

titrating 4ith -2%+2 using starch as an in$icat!r. "

4e can $etermine the am!unt !" + by titrating it

4ith -2%+2 4e can a#s! $etermine the am!unt !"

$iss!#ve$ !&ygen 3resent in the sam3#e. *hestarch is a$$e$ t!4ar$s the en$ !" the titrati!n t!3revent the stabi#iDati!n !" the 2

starch c!m3#e&. *he starch has a he#ica# structure an$ !nce the 2

is a$$e$ it 4i## be encage$O 4ithin the he#i& an$achieving the en$3!int 4i## be $icu#t.

n this e&3eriment 4e use$ an i!$!metrictitrati!n. *he $ierence bet4een i!$!metric an$i!$imetric titrati!n is the ch!ice !" ana#yte an$titrant. n i!$!metric titrati!n s!$ium thi!su#"ateis use$ as the titrant an$ the ana#yte is i!$ine4hi#e in i!$imetric titrati!n i!$ine is the titrantan$ the ana#yte is s!$ium thi!su#"ate.

'ith a## the $ata gathere$ 4e are ab#e t!ca#cu#ate the m!#arity !" the stan$ar$ Na2-2%+

s!#uti!n. ;sing the st!ichi!metric rati! 4ec!nverte$ the m!#es !" the 3rimary stan$ar$ t!the m!#es !" the titrant $ivi$e$ by the t!ta#v!#ume c!nsume$ "!r the titrati!n an$ mu#ti3#ie$by the a#i:u!t "act!r. verage m!#arity !" Na2-2%+

4as 0.0111849157∨approximately0.0112 . *he

m!#arity !" Na2-2%+ 4as then use$ t! ca#cu#ate the33m !" the 4ater sam3#e. 'e !btaine$ a va#ue !"

1.550878041 ppmO2 an$ "r!m the tab#e be#!4

% C!ntent (33m

%2) 20R C 'ater Qua#ity79

6. .9

.< B 6.6

e#!4 .<

0 2

C#ean g!!$ 4ater

-#ight#y 3!##ute$

M!$erate#y 3!##ute$ can

sustain #i"e !" 4arm 4ater

8shes

Aigh#y 3!##ute$

Cann!t sustain #i"e4e can see that the 4ater sam3#e cann!t sustain#i"e an$ is high#y 3!##ute$.

-!me "act!rs may aect the resu#ts !btaine$"r!m the e&3eriment #ie instea$ !" ten minutesthe sam3#e s!#uti!n is ma$e t! stan$ !vernightbe"!re ana#ysis. *he eect !" this !n the $iss!#ve$!&ygen c!ntent 4!u#$ be in$eterminate becausethe sam3#e might have heter!tr!3hic an$

3h!t!synthetic !rganisms that may 3er"!rmce##u#ar res3irati!n an$ 3h!t!synthesis. n !thercases 4herein the Mn-% is a$$e$ an$ thes!#uti!n ma$e t! stan$ "!r an h!ur be"!re the



J.N. Macabata / Chemistry 26.1 (2016) P a g e |

a#a#ine s!#uti!n is a$$e$ may resu#t t! a$ecrease t! the $iss!#ve$ !&ygen c!ntent !" the4ater sam3#e. *he manganese 4i## un$erg!re$ucti!n since it is #ight sensitive an$ 4i## causea $ecrease t! b!th the v!#ume !" the titrant an$the c!ncentrati!n !" $iss!#ve$ !&ygen.

>rr!rs in every e&3eriment is inevitab#e an$

3re$icti!ns !" their 3!ssib#e eects !n the resu#tsmay he#3 $etermine 4hat t! $! t! c!rrect theman$ i" 3!ssib#e t! av!i$ them. P!ssib#e s!urces !" err!rs in the c!n$ucte$ e&3eriment may be theinc!rrect !r$er !" a$$ing reagents in the 4atersam3#e. *he a$$iti!n !" 3h!s3h!ric aci$ be"!re3!tassium i!$i$e 4i## #ea$ t! the "!rmati!n !" i!$ic aci$.

%+ F AF G A%+ HI

Conclusion and Recommendations

References

na#ytica# Chemistry ca$emic Sr!u3 na#ytica#

Chemistry 5ab!rat!ry Manua# (>#ementaryQuantitative n!rganic na#ysis Chem 26.1)201+ +0

'in#er 5.'. ie estimmung $es in 'asserge#Tsten -auerst!en. erichte $er eutschenChemischen Sese##scha"t 1777 21? 27+B27<<.



J.N. Macabata / Chemistry 26.1 (2016) P a g e | <

Appendix (sing#e c!#umn "!rmat

A. Answers to Questions (if necessary)

B. i!ures (if necessary)

C. Raw Data "a#le (if necessary)

D. $or%in! &'uations

&. ample Calculationstandardiation of *a++,- olution

Primary stan$ar$ use$? %+

E!rmu#a Mass !" 1R stan$ar$? 21.0U Purity !" 1R stan$ar$? 99. U'eigh !" stan$ar$ g? 0.1<7V!#ume !" stan$ar$ s!#uti!n? 100 m5

*ria# 1 2 +

V!#ume !" %+ stan$ar$ m5 10 10 10

Eina# v!#ume !" Na2-2%+ m5 +7.7 2 0.

nitia# v!#ume !" Na2-2%+ m5 0 < 0

Net v!#ume !" Na2-2%+ m5 +7.7 +.0 0.

M Na2-2%+ *ria# 1?

0.1584g x 1mol

214.0 g x6 molNa

2S

2O

3

1molKIO3

x 0.994

0.0388 x 10

100

W 0.01137751228 X 0.011

*ria# 2?

0.1584g x 1mol

214.0 g x6 molNa

2S

2O

3

1molKIO3

x 0.994

0.0370 x 10

100

W 0.011++0761++ X 0.011+

*ria# +?

0.1584g x 1mol

214.0 g x6molNa

2S

2O

3

1molKIO3

x 0.994

0.0407 x 10

100

W 0.01076++< X 0.0107

verage M Na2-2%+ 0.01137751228+0.01133086133+0.0108463735

3=




ample Analysis5!cati!n !" -am3#ing? nstitute !" Mathematics "r!ntyar$ *!ta# V!#ume !" -am3#e? <00 m5

*ria# 1 2 +

Eina# v!#ume !" Na2-2%+ m5 1.<0 6.20 +

nitia# v!#ume !" Na2-2%+ m5 0 < 1.<0

Net v!#ume !" Na2-2%+ m5 1.<0 1.20 1.<0

% c!ntent 33m %2 *ria# 1?

0.0015 L x 0.0111849157 mol L

x 4molO2

1mol S2

O3

x 31.998g1molO

2

0.00150

¿1.43157973≈1. +

*ria# 2?

0.0015 L x 0.0111849157 mol

L x

4molO2

1mol S2 O3

x 31.998g

1molO2

0.00120=

*ria# +?

0.0015 L x 0.0111849157mol

L x

4molO2

1mol S2O3

x 31.998g

1molO2

0.00150

¿1.43157973≈1. +

verage % c!ntent 33m %2 1.43157973+1.789474663+1.4317973

3

=1.550878041

- RSD=

0.2065679575

1.550950564 x1000 ppt =133.1879702 ppt

C!n8$ence nterva# 1.<<07701 Y 0.2

,ther remar%s



J.N. Macabata / Chemistry 26.1 (2016) P a g e |

atq experiment 8 chem 26.1

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