SPECTROPHOTOMETRIC DETERMINATION DETERMINATION OF THE EQUILIBRIUM CONSTANT CONSTANT OF A REACTION V.G. ESTRADA 1 AND J.E.F LU2 1 NATIONAL NATIONAL INSTITUTE OF PHYSICS, PHYSIC S, COLLEGE OF SCIENCE 2 DEPARTMENT DEPARTMENT OF CHEMICAL ENGINEERING, COLLEGE OF ENGINEERING UNIVERSITY OF THE PHILIPPINES, DILIMAN QUEZON CITY, CITY, PHILIPPINES DATE DATE PERFORMED: PERFO RMED: AUGUST 26, 2015 INSTRUCTOR’S NAME: MARK NEIL TOLENTINO ______________________________________ _________________________________________________________ ______________________________________ _________________________ ______ ____________________________ ____________________________ ABSTRACT This This exper experi ie! e!"" #is #is $#% $#% "& 'e"er 'e"eri i!e !e "he "he #!#( #!#()" )"i* i*#( #( +#e +#e(e! (e!-" -"h h &. "he "he 21 "hi&*)#!#" "hi&*)#!#"e/ir&!$ e/ir&!$III% III% *&p(ex $0Fe$SCN% $0Fe$SCN% %, $3% "& 'e"eri!e "he e45i(i3ri5 *&!s"#!" *&!s"#!" $6 e4 % % .&r "he .&r#"i&! &. 0Fe$SCN%21 , #!' $*% "& *#(*5(#"e .&r "he e4 per*e!" 'i7ere!*e 3e"+ee! "he #er#-e 6 e4 e4 #!' "he (i"er#"5re #(5e8 S&(5"i&!s +i"h +i"h #r) #r)i!i!- #&5 #&5!" !"s s &. FeC( FeC( 9, 6SCN 6SCN,, #!' #!' HC( HC( +ere +ere :rs" :rs" prep prep#r #re' e'88 Thei Their r #3s& #3s&r3 r3#! #!*e *es s #!' #!' "he "he #!#() #!#()"i "i*# *#(( +#e +#e(e! (e!-" -"h h +ere +ere &3"# &3"#i! i!e' e' 5s 5si! i!- UV/V UV/Vis is spe*"r&ph&"&e"er8 Spe*i:* #(5es +ere 5se' "& *#(*5(#"e .&r "he *&!*e!"r#"i&! &. .erri* $0Fe 91 e4 %, %, "hi&*)#!#"e $0SCN e4 %, %, #!' "he 6 e4 e48 The per*e!" 'i7ere!*e +#s "he! *#(*5(#"e' #!' i" *#! 3e i!.erre' "h#" "he experie!" +#s !&" s5**ess.5( 3e*#5se &. experie!"#( err&rs8 The si-!i:*#!*e &. "his s"5') is "h#" "hr&5-h spe*"r&ph&"&e"r), 5!;!&+! s53s"#!*es *#! 3e i'e!"i:e' #!' &3sere' +i"h&5" #*"5#(() "&5*hi!- "he8 Spe*"r&ph&"&e"r) is #i!() 5se.5( .&r s53s"#!*es "h#" i-h" 3e "&xi*8 ______________________________________ _________________________________________________________ ______________________________________ _________________________ ______ ____________________________ ____________________________
INTRODUCTION
Spect!p"!t!#et$ %& ' #et"!( t! #e'&)e "!* #)c" ' c"e#%c'+ &)&t'-ce '&! '&!& & +%."t +%."t $ #e'&) #e'&)%-. %-. t"e %-te-& %-te-&%t$ %t$ !/ +%."t +%."t '& ' e'# e'# !/ +%."t +%."t p'&&e& p'&&e& t"!)." &'#p+e &!+)t%!- T"e '&%c p%-c%p+e %& t"'t e'c" c!#p!)-( '&!& ! t'-&#%t& +%."t !e ' cet'%- '-.e !/ *'e+e-.t" T"%& #e'&)e#e-t c'- '+&! e )&e )&e( t! #e'&)e )e t"e '#!)#!)-tt !/ ' -!* -!*- c"e c"e#%c' %c'+ &)& )&t'-c t'-ce e T"e 3)'-t%t't%e &t)($ )t%+%4e& t"e (e%ce c'++e( &pect!p"!t!#ete T"e (e%ce "'& t*! #'%- p't&, t"e &pect!#ete t"'t e#%t& ' &pec%c +%."t *'e+e-.t" '-( t"e p"!t!#ete t"'t #e'&)e& #e'&)e& t"e +%."t %-te-&%t$ *"%c" t"e &'#p+e t'-&#%tte( T"e #'%- .!'+ !/ epe%#e-t %& t! &t)($ e3)%+%%)# c!-&t'-t !/ e'ct%!- t"!)." t"!)." '-'+$&%& $ &pect!p"!t!#et$ T"e epe%#e-t %-te-(& t! /'#%+%'%4e &t)(e-t& *%t" t"e &pect!p"!t!#ete '-( *%t" ' -e* #et"!( !/ !t'%-%-. t"e e3)%+%%)# c!-&t'-t !/ ' e'ct%!- T"e e'ct%!- et*ee-
%!- '-( t"%!c$'-%te %& )t%+%4e( %- t"%& epe%#e-t It "'& t"e e'ct%!- &$&te#, Fe3+
+ SCN-(aq) ↔ FeSCN2+(aq) + H2O()
(aq)
I- t"%& e'ct%!e'ct%!- &$&te#, &$&te#, +!!( 7e( 7e( c!#p+e c!#p+e 8Fe9 8Fe920;59SCN;<2= %& /!# /!#e( e( T"e '&!'-ce !/ t"%& c!#p+e *%++ e #e'&)e( $ t"e U>?>%& &pect!p"!t!#ete '-( '-( t"e t"e c!-c c!-cee-t t't 't%! %!- c'c'- t"et"e- e !t' !t'%%-e( e( t" t"!)." !)." t"e t"e )&e )&e !/ t"e t"e @ee @ee?? L'#et’& L'* It e+'te& t"e +%."t '&!pt%!- !/ t"e c!+!e( &)&t'-ce %- t"e &$&te# t! %t& c!-ce-t't%!- It "'& t"e e3)'t%!-, A ! "#$
"ee, AB '&!'-ce B #!+' '&!pt%%t$ c!e//%c%e-t %- M?1 c#?1 B p't" +e-.t" c B '-'+$te #!+' c!-ce-t't%!%t" t"e )&e !/ t"e c'+c)+'te( c!-ce-t't%!-, t"e e3)%+%%)# c!-&t'-t c'- e c!#p)te( )&%-. t"e epe&&%!-, 2+ % eq ' &Fe3+' &SCN-' eq ! &FeSCN
T"e #et"!( c'- !-+$ e eec)te( eec)te( 'cc)'te+$ %/ t"e &!+)t%!-& )&e( 'e "%."+$ (%+)te( '-( t"e e'.e-t& "'e ' "%." p)%t$ ! e+&e t"e ('t' *%++ -!t e %- ' e.e&&%-. p'tte- I- '((%t%!- t! t"'t, t"e epe%#e-t #)&t e pe/!#e( *%t" pec%&e+$ &'#e te#pe't)e /! '++ &!+)t%!-& &%-ce K e3 e3 c"'-.e& *%t" te#pe't)e RESULTS AND DISCUSSION
A/te t"e c'+%'t%!- !/ t"e &pect!p"!t!#ete, t"e )--!*- &!+)t%!-& 'e te&te( A-!t"e +'- &!+)t%!- *'& pep'e( '-( )&e( /! t"%& p't !/ t"e epe%#e-t t! ec'+ ec'+% %' 'te te t"e t"e '&e '&e !/ 4e 4e! !/ t"e t"e 'pp' 'pp'' 't) t)& & &%-c &%-ce e t"e t"e '#!) '#!)-t -t '-( '-( t"e t"e ? c!-ce-t't%!c!-ce-t't%!- !/ SCN )&e( %- t"%& p't (%e& /!# t"'t !/ t"e &t'-('( &!+)t%!-& ee- %/ t"e &'#e c)ette *ee )&e( I- t"%& p't !/ epe%#e-t, #!e (%+)te( c!-ce-t't%!- !/ SCN ? '-( Fe= %& )&e( T"%& %& t! %&!+'te t"e #et'+ c!#p+e 8FeSCN2=< It %& p!&&%+e &%-ce %- (%+)te( /!#, SCN ? '-( Fe= "'e -e.+%.%+e
'&!'-ce I- '((%t%!-, t"%& t$pe !/ &pect!#et$ c'- !-+$ $%e+( e&)+t& %/ t"e &!+)t%!-& t! e '-'+$4e( 'e "%."+$ (%+)te( '-( c!#e /!# e'.e-t& *%t" "%." p)%t$ T"!)." '+.e'%c #'-%p)+'t%!- !/ t"e t"e e3)'t%!- !/ t"e e&t t c)e, ! 2*,. / 0.00,1
T"e e3)%+%%)# c!-ce-t't%!c!-ce-t't%!- !/ t"e 8FeSCN 8FeSCN2=< *%++ e !t'%-e( L%&te( %- t"e t'+e e+!* %& t"e c'+c)+'te( 8FeSCN2=
6010? 010? 1010?
1010 ? 1010 ? 1010 ?
A/te !t'%-%-. t"e e3)%+%%)# c!-ce-t't%!-& '-( t"e %-%t%'+ c!-ce-t't%!-& !/ t"e e'ct'-t&, t"e e3)%+%%)# c!-ce-t't%!-& !/ Fe = '-( SCN? *ee c'+c)+'te( )&%-. t"e ICE T'+e '& &"!*- e+!* Ta#e ,. ICE T'+e !/ C!-ce-t't%!-& &Fe3+ &SCN- &FeS ' ' CN2+' I767a 8Fe= 8SCN?< 0 <% % C:a;e ?J ?J J = ? Eq577#<75 8Fe 8SCN < J = <%?J %?J
C'+c)+'te( '+)e& /! t"e e3)%+%%)# c!-ce-t't%!- !/ t"e e'ct'-t& '-( p!()ct& p !()ct& 'e &"!*- %- t"e t'+e e+!* Ta#e . E3)%+%%)# C!-ce-t't%!-& C!-ce-t't%!-& 3+ S567 &Fe 'eq &SCN-'eq &FeSCN2+ 'eq 1 11 10 ? 10? 10? 2 6 162 10 ? 10? 10? 0 0 1H 10 ? 10? 10?
A/te .'t"e%-. '++ t"e %-/!#'t%!- e.'(%-. t"e e3)%+%%)# c!-ce-t't%!-& !/ t"e )--!*-, t"e e3)%+%%)# c!-&t'-t c'- -!* e !t'%-e( *%t" t"e )&e !/ t"e epe&&%!-, 2+ % eq 'eq &Fe3+'eq &SCN-'eq eq ! &FeSCN
%t" '++ t"e pet%-e-t %-/!#'t%!- .'t"ee(, 'e t"e- c'+c)+'te( T"e e3)%+%%)# c!-&t'-t& !t'%-e( 'e &"!*- %- t"e t'+e e+!* Ta#e >. E3)%+%%)# C!-&t'-t U4 S567 Eq577#<75= C86a68 1 2 2 00 055 Ae: 2H
"e- c!#p'e( t! t"e t"e!et%c'+ '+)e !/ K e3 *"%c" %& H0 T"e pece-t e! %& '!)t 66H *"%c" '&%c'++$ #e'-& t"'t t"e epe%#e-t't%!- "'& *%(e #'.%- !/ e!& e!& T"e p!&&%+e e e!& !& t"'t 'ecte( t"e epe%#e-t'+ epe%#e-t'+ '+)e& 'e +%&te( %- t"e t'+e e+!* e+!* Ta#e *. S!)ce& !/ E!& S5<$e8 ? De6e<=7a6 E<<<8 e I@e6e<=7 a6e I-c!-&%&te-t I-(ete#%-'t R!!# e Te#pe't) Te#pe't)e e N!t p!pe+$ p!pe+$ Dete ete# #%-' %-'te %-&e( c)ette I-'cc)'te Dete ete# #%-' %-'te '#!)-t !/ &'#p+e N!t N!t e-!) e-!)." ." Dete ete# #%-' %-'te (%+)t%!I#p) p)%t$ %t$ !/ Dete ete# #%-' %-'te t"e e'.e-t&
S86e=a67$ Ra@=G< 88
R'-(!# S$& S$&te# te#'t%c 't%c S$& S$&te# te#'t%c 't%c S$& S$&te# te#'t%c 't%c S$& S$&te# te#'t%c 't%c
CONCLUSION AND RECOENDATION
T"e epe%#e-t epe%#e-t #'(e )&e !/ t"e @ee?L'#et’& @ee?L'#et’& +'* t! !t'%- t"e c'+%'t%!c)e c)e T"e e&t?t +%-e *'& (ete#%-e( (ete#%-e( t"!)." e.e&&%! e.e&&%!- '-'+$&%& '-'+$&%& '-( t"e e3)'t%!- %& $ B 1665 = 006 T"e +%-e'%t$ c!ec%e-t %& 2 B 01H T"%& %& -!t '- 'ccept'+e '+)e ec')&e %t (e%'te& /!# t"e %(e'+ '+)e T"e c'+c)+'te( 'e'.e '+)e !/ K e3 e3 %& 51H5 '-( ' 16H (%ee-ce t! t"e +%te't)e '+)e *'& '+&! c!#p)te( T"%& .!e& t! &"!* t"'t t"e epe%#e-t *'& -!t &)cce&&/)+ T"e +'.e pece-t (%ee-ce %& ()e t! epe%#e-t'+ e!& S!#e !/ t"e &!)ce& #'$ %-c+)(e t"e %#p!pe "'-(+%-. !/ t"e c)ette, %-'cc)'c$ !/ t"e '#!)-t !/ &!+)t%!-& )&e(, !e?(%+)t%!- ! -!t e-!)." (%+)t%!-, '-( %#p)%t$ !/ &)&t'-ce& I- !(e t! "'e ette e&)+t&, %t %& ec!##e-(e( t! )&e &!+)t%!-& t"'t 'e #!e (%+)te( '-( t! )&e &)&t'-ce& *%t" "%."e p)%t$ REFERENCES 81< Pet)cc%, R , e%-., F, F, M'()', , @%&&!--ette, @%&&!- -ette, C Ge-e'+ C"e#%&t$ C" e#%&t$ 10 t" e( Pe'&!- E()c't%!-, C'-'(' 2011 82< S%+ee S%+ee., ., M S P%-c%p+ P%-c%p+e& e& !/ Ge-e'+ Ge-e'+ C"e#%&t C"e#%&t$ $ ( e( T"e McG'*?%++ C!#p'-%e&, I-c, Ne* ! 201 8< McG'*?%++ O-+%-e Le'-%-. Ce-te T"e I#p!t'-ce !/ Spect!p"!t!#et$ "ttp:"%."ee(#"e()c't%!-c!#&%te&0001216&t)(e-t_%e*0eec%&e&pe ct!p"!t!#et$_%#p!t'-ce"t#+ 9'cce&&e( )-e 2, 2015;
