Experiment – ELECTROCHEMICAL ANALYSIS OF FERRICYANIDE USING CYCLIC VOLTAMMETRY 2013-19846; 2013-67188 November 17, 2016 I.
Abstract Cyclic voltammetry is classified as a type of potentiodynamic electroanalytical technique used for the study of electroactive species and is extensively utilized in industrial applications and academic research laboratories. In this experiment, the formal reduction reduction potential potential of ferricyanide ferricyanide was determin determined ed to be 0.21! 0.21! " while in contrast, the theoretical formal reduction potential is 0.# ". $he effect of scan rate and concentration on pea% current was observed. &ea% current was determined to be directly proportional to both the square root of scan rate 'v 1(2 ) and concent concentrati ration. on. *sin+ *sin+ two standard standard curves curves of Ip ox and Ip red a+ainst a+ainst concentration, the concentration of the un%nown was obtained usin+ the linear mM equations. $he concentration of the un%nown was determined to be 7.55 . II. Keywords: Keywords: Formal e!"#tion $otential, %#an ate, &no!i# $ea' ("rrent, (at)o!i# $ea' III. Introduction (*#li# voltammetr* i+ a i!el* "+e! te#)n te#)ni" i"e e in or!er or!er to a#" a#"ire ire "ali "alitat tative ive in.o in.orm rmat atio ion n abo" abo"tt t)e t)e ele# ele#tr tro# o#)e )emi mi#a #all rea#tion+ o##"rrin/ ar! Fa"l'ner, 2008 5t /ive+ a "i#' lo#ation o. re!ox potential+ o. t)e t)e +pe#ie +pe#ie+ + .o"n .o"n! ! to be ele#tr ele#troa oa#ti #tive ve ar! Fa"l'ner, 2008 & (*#li# voltammeter voltammeter #on+i+t o. t)ree main part+ namel* a or'i r'in/ ele# ele#tr tro! o!e, e, a re.e re.ere ren# n#e e ele# ele#tr tro! o!e e an! an! a #o"nter ele#tro!e ar! Fa"l'ner, 2008 & rever+ible ele#tro#)emi#al ele#tro#)emi#al rea#tion t)e #*#l #*#li# i# volt voltam amme metr* tr* pro! pro!"# "#e+ e+ )ave )ave ell ell !e.ine! #)ara#teri+ti#+ +"#) a+ t)e ratio o. t)e pea' #"rrent+ i+ e"al to one, )e pea' #"rrent+ are proportional to t)e +"are root o. t)e +#an rate, an! )e po+ition+ o. pea' volta/e !o not alter a+ a ."n#tion o. volta/e +#an rate niver+it* o. (ambri!/e, 201 )e +t"!* +t"!* aim+ aim+ to #reate #reate a #*#li# #*#li# voltammetr* in or!er to t)e .ormal re!"#tion poten potentia tiall E0 o. t)e Fe Fe555( 55(N N 6 3- < 4Fe55(N 6 #o" #o"plin lin/, to !e.in .ine t)e t)e #on+e"en#e+ o. +#an rate an! #on# #on#en entr trat atio ion n vari varian antt o. = 3Fe(N6 on pea' #"rrent, an! to "anti.* t)e #on# #on#en entr trat atio ion n o. "n'n "n'no on n = 3Fe(N 6 +ol"tion Ele#tro#)emi+tr* - (*#li# Coltammetr* $a/e 1
:Fe0(N38;3- > e-
:Fe0(N36;4-
IV. Experimental . -toc% &reparation &reparation %to#' %ol"tion & 16462 / o. = 3Fe(N6 a+ !il" !il"te te! ! it) it) 01? 01? @NA @NA 3 in a 100 ml vol"metri# .la+' in or!er to prepare 0 m? =3Fe(N6 +to#' +ol"tion Beterminin/ t)e Formal e!"#tion $otential an! t)e e..e#t o. %#an ate &n ali"ot o. 4 ml o. t)e +to#' +ol"tion a+ !il"te! in a 0 ml vol"metri# .la+' in or!er to prepare a 4 m? = 3Fe(N6 +ol"tion Beterminin/ t)e E..e#t o. Car*in/ %#an ate an! (on#entration & var*in/ #on#entration #on#entration o. =3Fe(N6 a+ prepare! in 0 ml vol"metri# .la+' at #on#entration+ o. 2,4,6, 8, 10 m? o. = 3Fe(N6 +ol"tion +ol"tion !il"te! !il"te! it) 01? @NA 3
)e +tep+ .or .ormal re!"#tion $otential a+ repeate! at var*in/ +#an rate o. 0, 100, 160, an! 200 mC<+ )e pea' oxi!ation an! pea' re!"#tion a+ !etermine! b* +it#)in/ t)e /rap) to 5E v+ time )e pea' oxi!ation an! re!"#tion a+ plotte! a/ain+t v 1<2 an! t)e e..e#t o. +#an rate a+ t)en eval"ate!
immer+e! in an "n+tirre! +ol"tion an! mea+"rin/ t)e re+"ltin/ #"rrent &n!er+on, 1991 5n #*#li# voltammetr* t)e potentio+tat applie+ t)e !e+ire! potential beteen a or'in/ ele#tro!e /la++* #arbon an! a re.eren#e ele#tro!e Ag/AgCl) 5n a!!ition, t)e or'in/ ele#tro!e i+ t)e lo#ation )ere t)e rea#tion bein/ +t"!ie! ta'e+ pla#e )e a"xiliar* ele#tro!e, t*pi#all* platin"m ire, /enerate+ t)e #"rrent polariDe! nee!e! to maintain ele#trol*+i+ at t)e or'in/ ele#tro!e )e potential o. t)e or'in/ ele#tro!e i+ #ontrolle! ver+"+ a re.eren#e ele#tro!e +"#) a+ a &/<&/(l ele#tro!e )i#) maintain+ #on+tant potential polariDe! &n!er+on, 1991 )e #"rrent re+pon+e .rom an ex#itation potential i+ mea+"re! an! a #*#li# voltammo/ram #"rrent-potential plot re+"lt+ & +#an per.orme! toar!+ a more po+itive potential i+ #alle! an )e ano!i# +#an i+ per.orme! toar!+ a more po+itive potential )erea+ a #at)o!i# +#an i+ toar!+ t)e !ire#tion o. a more ne/ative potential )e re!"#tion potential o #an t)en be #al#"late! "+in/ t)e .orm"la belo an! t)e .olloin/ parameter+ E pa+ E pc o E =
/. /etermination of the concentration of the un%nown 3 #4e'C5) 6 solution
Initial7 8900 m"
. /eterminin+ &otential
the
ormal
eduction
)e E#or!er an! $otentio+tat ere +et "p it) t)e or'in/ ele#tro!e poli+)e! "+in/ "e)ler #lot) it) al"mina )e ioniDer+ ere rin+e! an! !r* be.ore +et"p & 2ml o. 4m? = 3Fe(N 6 +ol"tion a+ "+e! a+ t)e +tan!ar! )e /reen #lip a+ atta#)e! to t)e or'in/ ele#tro!e, t)e re! to t)e #o"nter ele#tro!e an! t)e *ello to t)e re.eren#e ele#tro!e )e parameter+ ere +et "p it) t)e initial an! t)e .inal bot) -800mv, t)e rate a+ +et to100mC<+, "pper limit a+ +et to 800mC, an! t)e loer limit a+ +et to -800mC )e +#an+ ere obtaine! an! t)e Epa an! E p# a+ !etermine! in or!er to #al#"late .ormal re!"#tion potential C. /eterminin+ the ffect of -can ate
& +tan!ar! #"rve a+ ma!e b* repeatin/ t)e +tep+ in !eterminin/ t)e .ormal re!"#tion potential "pon var*in/ t)e #on#entration o. = 3Fe(N 6 "+in/ 2,4,6,8,10 m? = 3Fe(N 6 +ol"tion+ )e pea' oxi!ation an! re!"#tion a+ plotte! a/ain+t #on#entration an! eval"ate! t)e e..e#t o. #on#entration on t)e pea' #"rrent )e +tan!ar! #"rve a+ "+e! to #al#"late t)e #on#entration o. t)e "n'non +ample V. Results and Discussion (*#li# voltammetr* )a+ t)e abilit* o. rapi!l* ob+ervin/ re!ox be)avio"r over a i!e potential ran/e 5t involve+ #*#lin/ o. t)e potential o. an ele#tro!e, )i#) i+ Ele#tro#)emi+tr* - (*#li# Coltammetr* $a/e 2
2
inal7 8900 m" ate7 100 m"(s *pper limit7 900 m" :ower limit7 8900 m" )e ano!i# potential an! #at)o!i# potential .or t)e re!ox rea#tion o. .erri#*ani!e a+ re#or!e! to be 0260C an! 01680C re+pe#tivel* %"b+e"entl*, t)e re!"#tion potential o a+ #al#"late! to be 0216 C )e t)eoreti#al re!"#tion potential o. .erri#*ani!e )oever i+ 036 C %tan!ar! e!"#tion $otential+ E0, 2o(, n!
Table 1. Data fo I! o" a#$ I! e$ at %a&'#g (a# ate(
Sa# ate +, 1,, 1, *,,
Sa# ate1/* -.,-1, 1, 1*.231 1 12.12*1 2
Table 2. Data f o
I! o" a#$ I! e$ at %a&'#g o#e#tat'o#( of fe'&a#'$e
I! o"
I! e$
0.1* +.+0
2.+-30 .2,01
-.,3-
3.21 1,.13*-
3.1,2
Co#e#tat'o # * 2 1, U#>#o<#
I! o" *.3++.+0 3.1-*,2 1*.,221 12.033 11.+133
I! e$ 2.+-30 .2,01 11.2+12.2+1-.23* 10.2+1
1+ 1, f4") 5 ,.-2" 1.+ R7 5 1
+ Current
, + 1,
-
3 1, 11 1* 10 12 1+
f4") 5 ,.--" 6 ,.*R7 5 ,.3*
1+ Scan rate1/2
*, 1+ 1, + , Current + 1 1, 1+ *,
f4") 5 1.2+" 6 ,.1R7 5 1 *
0 2 + - 3 1, 11 f4") 5 1.1" 1.- R7 5 ,.33
Concentration
F'g8e 1. 9lot of I! o" a#$ I! e$ aga'#(t (a# ate1/*: (;o<'#g t;e e=et of (a# ate.
)e e..e#t o. +#an rate v on #*#li# voltammo/ram+ o. 4 m? = 3Fe(N6 in 01? =NA3 a+ ob+erve! at 0, 100, 160, 200 mC<+ 5t a+ !etermine! t)at pea' #"rrent i+ !ire#tl* proportional to v 1(2 5t i+ important to note t)at a+ +#an rate i+ !e#rea+e! t)e #*#li# +eep o. t)e voltammo/ram ill ta'e lon/er to re#or! )i+ !ata a/ree+ it) an!le+-%ev#i' e"ation at 2(, )erein, n i+ t)e n"mber o. ele#tron+, & i+ t)e ele#tro!e area m 2, ( i+ t)e #on#entration mol<, B i+ t)e !i.."+ion #oe..i#ient m 2<+ an! v i+ t)e potential +#an rate C<+; a+ +#an rate in#rea+e+ pea' #"rrent in#rea+e+
Ele#tro#)emi+tr* - (*#li# Coltammetr* $a/e 3
F'g8e *. 9lot of I! o" a#$ I! e$ aga'#(t o#e#ta'o#: (;o<'#g t;e e=et of o#e#tat'o#.
5t a+ !etermine! t)at #on#entration a..e#t+ t)e ma/nit"!e o. t)e pea' #"rrent Fi/"re 2 +)o+ t)e pea' #"rrent+ at var*in/ #on#entration+ o. 2, 4, 6, 8, an! 10 m? o. =3Fe(N6 in 01 ? =NA3 at 100 mC<+ )e !ata +)o+ t)at pea' #"rrent i+ !ire#tl* proportional to #on#entration )i+ +tan!ar! #"rve #an t)en be "tiliDe! to eval"ate t)e #on#entration o. t)e "n'non +in#e t)e 5p ox an! 5p re! o. t)e "n'non a+ obtaine! to be 11199 m& an! -13481 m& re+pe#tivel*
ob+erve! an! vi+"aliDe! on t)e voltammo/ram+ Finall*, t)e #on#entration o. t)e "n'non a+ extrapolate! "+in/ t)e +tan!ar! #"rve -ample computations for un%nown *sin+ Ip ox 7 11.!1;; y =1.4508 x + 0.1744
x =
11.5199 ¿= 1.4508 x + 0.1744
11.5199− 0.1744 1.4508
VII Reference &n!er+on, & G 1991 :C$=C>?I-$@ etrieve! .rom $@&5?E%: )ttp:<<p)attime+#om
x =7.82 mM *sin+ Ip red 7 81#.<9!1
ott, & H, Ga#'+on, $ 1996 %t"!* o. Ferri#*ani!e b* (*#li# Coltammetr* +in/ t)e (C-0H Current -eparations4
y =−1.6111 x −1.7619
(
13.4851
−
x =
5t i+ re#ommen!e! t)at be.ore ea#) part o. t)e met)o!olo/*, t)e or'in/ ele#tro!e be poli+)e! "+in/ a "e)ler #lot) it) al"mina at +"..i#ientl* in or!er to obtain better re+"lt+ in t)e voltammo/ram+
)
1.6111 x −1.7619
=−
ar!, & G, Fa"l'ner, 2008 lectrochemical ?ethodsA undamentals and pplications.
−13.4851 + 1.7619 −1.6111
x =7.28 mM
(on#entration o. "n'non
¿
7.82 + 7.28 2
¿ 7.55 mM
VI Conclusion )e ele#tro#)emi#al anal*+i+ o. .erri#*ani!e, =3Fe(N6, "+in/ #*#li# voltammetr* a+ +"##e++."ll* per.orme! in !eterminin/ t)e .ormal re!"#tion potential o. .erri#*ani!e )e e..e#t+ o. +#an rate an! #on#entration on t)e pea' #"rrent+ ere Ele#tro#)emi+tr* - (*#li# Coltammetr* $a/e 4
Ni#)ol+on, % 196 )eor* an! &ppli#ation o. (*#li# Coltammetr* .or ?ea+"rement o. Ele#tro!e ea#tion =ineti#+ nal. Chem $an!"ran/a#)ar, ?, %am*, E, ()an!ra+)e'ar, N, Iilbert, A, e!!*, %, %%)eri/ara, 2010 Ele#tro#)emi#al 5nve+ti/ation+ o. $ota++i"m Ferri#*ani!e an!Bopamine b* 1-b"t*l-4met)*lp*ri!ini"m tetra.l"oro borate ?o!i.ie! (arbon $a+te Ele#tro!e: & (*#li# Coltammetri# %t"!* International Bournal of lectrochem -cience niver+it* o. (ambri!/e 201 :inear -weep and Cyclic "oltametryA $he &rinciples etrieve! .rom
Bepartment o. ()emi#al En/ineerin/ an! iote#)nolo/*: )ttp:<<#eb#ama#"'
Ele#tro#)emi+tr* - (*#li# Coltammetr* $a/e
+eep-an!-#*#li#-voltametr*-t)eprin#iple+
