GRAVIMETRIC GRAVIMETRIC ANALYSIS ANALYSIS OF O F A CHLORIDE SALT Report Submitted by: Ron!d Mi!ner Lbortory prtner: "ie#$ Mnti% Lb &er'ormed: Februry ()t$* +,(+ Group: T$ur#dy A'ternoon* Group F Dte #ubmitted: Mr-$ (.t$* +,(+
&urpo#e: To determine t$e -$!oride -ontent o' n un%no/n #o!ub!e #!t /$i!e i!!u#trtin0 t$e te-$ni1ue# in2o!2ed in 0r2imetri- n!y#i#3 T$eory: In order to 'ind t$e -$!oride -ontent o' n un%no/n #o!ub!e #!t* t$t -$!oride -n 'ir#t be e4tr-ted 'rom t$e #o!ution in t$e 'orm o' pre-ipitte3 5$i!e #ome #ub#tn-e# re e#i!y #o!ub!e in /ter due to mo!e-u!r propertie#* ot$er# re not3 T$e#e propertie# -n be t%en d2nt0e o' /$en tryin0 to i#o!te prti-u!r ion3 6y imp!ementin0 re-tion t$t 'or !! inten#i2e purpo#e# 0oe# to -omp!etion* t$e C!7 ion -n be re-ted /it$ ot$er ion# to 'orm n in#o!ub!e #ub#tn-e3 T$i# ne/ #ub#tn-e /i!! pre-ipitte out o' #o!ution3 5it$ t$e u#e o' #toi-$iometry* t$e -$!oride -ontent o' t$e ne/ #ub#tn-e -n be -!-u!ted3 Common!y t$e 'ormtion o' #i!2er -$!oride i# u#ed to 'ind t$e -on-entrtion -$!oride ion#3 Precipitation of Chloride Ion by Addition of Silver Ion:
A0891 8 C!791 ;< A0C!9# T$ou0$ it i# ##umed t$t t$e bo2e re-tion 0oe# to -omp!etion due to A0C!9#=# e4treme in#o!ubi!ity* #ome A0C!9# doe# in '-t di##o!2e3 T$i# #o!ubi!ity -n be #$o/n by -!-u!tin0 t$e #o!ubi!ity produ-t " #p3 9( A0C!9# ;< A0891 8 C!791
" #p ; >A0891?@>C!791? ; (3) 4 (,7(,
5$i!e #i!2er -$!oride /i!! be in e1ui!ibrium /it$ it# ion# in t$e #o!ution* be-u#e " #p i# #o #m!!* t$e di##o!2ed ion# -n be -on#idered ne0!i0ib!e3 5$en A0NO i# dded to #o!ution -ontinin0 -ontinin0 C!7 ion#* di#p!-ement re-tion i# under0one nd t$e A08 nd C!7 ion# /i!! pre-ipitte out 1ui-%!y # A0C!9#* unti! !! o' t$e C! 7 i# -on#umed 9##umin0 C!7 i# t$e !imitin0 re0ent3 A #m!! mount o' #!t /i!! be !e't in #o!ution* depen din0 on t$e mount o' e4-e## A08 dded to #o!ution3 6e-u#e m4imum #o!ubi!ity /i!! o--ur /$en t$ere i# no e4-e## A08 ion pre#ent* t$e " #p 2!ue -n be u#ed to -!-u!te t$e reminin0 C!7 in /or#t -#e -ondition#3 5it$ no e4-e## A08* >A08? ; >C!7?B !et bot$ ; 4 " #p ; >A0891?@>C!791? ; (3) 4 (,7(, >4?@>4?;(3) 4 (,7(, 4 ;(3 4 (,7 6e-u#e t$e 'ormtion o' #o!id $ppen# #o '#t* it pre-ipitte# # /$t i# re'erred to # -o!!oid3 T$e prti-!e# re e4treme!y #m!! be-u#e t$ere i# no time 'or -ry#t! 'ormtion3 In order to -o!!e-t t$e pre-ipitte /it$out !o##e# t$rou0$ t$e 'i!ter pprtu#* t$e -o!!oid -n be en-our0ed to 'orm !r0er nd more -ry#t!!ine pie-e# /it$ 0ent!e $etin0 nd #tirrin0 in t$e pre#en-e o' nitri- -id3 T$e pre-ipitte /i!! turn into !r0er m##e# !e2in0 be$ind #emi7-!er !i1uid3 T$e nitri- -id pre2ent# re2er#ion o' t$e ne/!y 'ormed #o!id pie-e# to -o!!oid #tte3 T$e pre-ipitte -n t$en be 'i!tered nd m##ed 'or -!-u!tion3 F-tor# !edin0 to $i0$ re#u!t# 'or C!7 ion: Due to t$e rpid pre-ipittion o' A0C!9# to t$e -o!!oid #tte* ot$er ion# -n be-ome trpped t t$e #me time3 For t$i# re#on pre-ipittion i# -rried ou t #!o/!y in n -idi- #o!ution3 T$e -id #o!ution re#i#t# inter'eren-e 'rom nion# o' /e% -id# 9#u-$ # CO7+ /$i-$ -n !#o 'orm pre-ipitte# /it$ pre#ent #i!2er ion#3 5$i!e t$ere i# need 'or #ome e4-e## o' #i!2er ion#*
!r0e e4-e## -n re#u!t in e4tr un/nted pre-ipitte# /it$ #i!2er nd ot$er ion# in t$e #o!ution3 E4mp!e# o' inter'erin0 ion# in-!ude ny pre#ent ne0ti2e ion t$t /ou!d $2e !o/ #o!ubi!ity /$en -ombined /it$ #i!2er3 Inter'erin0 ion# -ou!d pre-ipitte /it$ t$e e4-e## A08 in t$e #o!ution re#u!tin0 in $i0$er m## o' pre-ipitte3 In-omp!ete /#$in0 or dryin0 o' pre-ipitte -n en-our0e t$e#e error# by !!o/in0 'or 3 F-tor# !edin0 to !o/ re#u!t# 'or C!7 ion: T$e #i!2er -$!oride pre-ipitte de-ompo#e# b-% into it# ion# in t$e pre#en-e o' !i0$t3 9+ A0C!9# ;< A09# 8 9(+C!+90 T$i# re#u!t# in 2io!et -o!our pperin0 on t$e pre-ipitte due to t$e --umu!tion o' #i!2er3 5$i!e t$i# -n $ppen rpid!y in #tron0 !i0$t* t$e de-ompo#ition /i!! $ppen min!y on t$e #ur'-e o' t$e pre-ipitte /it$ t$e in#ide bein0 prote-ted by t$e re-ted -otin0 'ormed on t$e out#ide* #o t$e e''e-t# #$ou!d not be too 0ret3 I' t$e de-ompo#ition #$ou!d o--ur /it$ #i0ni'i-nt e4-e## A08* #o!ub!e CIO7 -n be 'ormed re#u!tin0 in !o/ yei!d o' pre-ipitte* # #ome C!7 ion# /i!! be !o#t t$rou0$ t$e 'i!trtion pprtu#33 9 C!+90 8 H+,9! 8 A0891 ;< A0C!9# 8 CIO791 8 )H891 C!-u!tin0 C$!oride by 5ei0$t: 6y e1ution (: A0C!9# ;< A0891 8 C!791 number o' mo!e# A0C! ; number o' mo!e# C!7 #o: ( Con2ert m## o' pre-ipitte 9A0C! into mo!#: Mo!# A0C! ; 90rm# A0C! 90rm#mo! A0C!
+ Con2ert mo!e# o' -$!oride ion to m##: M## C!7 ; 9number o' mo!# C!7490rm#mo! C!7
#e m## o' C!7 to -!-u!te by m## o' ori0in! #mp!e: C! ; 9M## C!7 M## #mp!e4(,,
Lo##e#: In order to m%e #ure t$t -ertin un/ ted ion# re remo2ed 'rom t$e pre-ipitte* t$e #mp!e i# rin#ed /it$ bot$ (,,m! o' /ter nd m! portion# o' -etone3 6e-u#e A0C! doe# $2e 2ery #m!! #o!ubi!ity in /ter* rin#in0 /it$ /ter my -u#e #ome !o##e# t$rou0$ t$e 'i!ter pprtu#3 T$e /or#t -#e !o##e# -n be -!-u!ted u#in0 t$e " #p 2!ue3 " #p ; (3) 4 (,7(, mo!L ( C!-u!tin0 t$e mount o' A0C! t$n -n be di##o!2ed in (,,m! o' /ter:
Lo##e# in mo!# ; 9" #p93(L ; (3) 4 (, 7(( mo!# + -on2ertin0 to 0rm# 9(3) 4 (,7((mo!9(.3+ 0mo! ; +3 4 (,7 0 !o#t T$ere'ore in t$e /or#t -#e #-enrio* +3 4 (,70 or pre-ipitte -n be !o#t by rin#in0 /it$ (,, m! o' /ter3 &ro-edure: To be0in t$e !b* t$e #mp!e o' un%no/n #!t /# obtined nd t$e #mp!e number nd true C! by m## re-orded3 A $otp!te /# t$en prepred nd #et to $et to #ettin0 3 5$i!e t$e $otp!te /# pre$etin0* 3(+0 o' un%no/n #!t /# t$en /ei0$ed by di''eren-e in +, m! 0!## be%er3 (,, m! o' di#ti!!ed /ter /# t$en dded to t$e un%no/n #mp!e nd (m! o' HNO /# dded by TA3 T$e #o!ution /# t$en #tirred3 T$e ne-e##ry mount o' A0NO needed 'or re-tion /# -!-u!ted # (3 m! !on0 /it$ n ddition! m! e4-e## nd m! 'or !ter u#e3 T$e needed A0NO /# t$en obtined 'rom TA3 T$e -!-u!ted 2!ue o' A0NO !on0 /it$ m! e4-e## /# dded to t$e +,m! be%er -ontinin0 t$e un%no/n #mp!e nd p!-ed on t$e $otp!te3 T$e #o!ution nd pre-ipitte /# $eted* /it$ 0ent!e #tirrin0 t inter2!# in order to en-our0e -r y#t! 'ormtion3 Se2er! time# t$e #o!ution /# o2er$eted* re!e#in0 too mu-$ #tem3 5$en o2er$etin0 o--urred* t$e be%er /# remo2ed nd t$e temperture o' t$e $otp!te /# re#et be'ore p!-in0 t$e be%er b-% in it# ori0in! po#ition3 5$en t$e mority o' t$e pre-ipitte $d -o!!e-ted in !r0er pie-e# n d t$e #o!ution /# #emi7-!er* t$e #o!ution /# te#ted 'or -omp!etene## o' re-tion /it$ t$e pre2iou#!y -o!!e-ted m! o' A0NO3 No pre-ipitte 'ormed nd t$e re-tion ppered -omp!ete3 T$e +, m! be%er /# t$en p!-ed in dr/er to -oo! out o' dire-t !i0$t3 T$e m## o' t$e -ru-ib!e /# re-orded # (3) 0 nd initi!# /ere /ritten it in order to %eep tr-% o' di''erent #mp!e#3 5$i!e t$e #o!ution /# -oo!in0* ,m! o' ,3 ( M HNO /# -o!!e-ted 'rom TA 'or !ter u#e3 On-e t$e #o!ution /# #!i0$t!y /rmer t$n room temperture it /# 'i!tered u#in0 2-uum 'i!ter pprtu#3 (, m! o' t$e ,3( M HNO /# dded to t$e be%er nd #/ir!ed* bein0 u#ed to di#!od0e pre-ipitte into t$e -ru-ib!e'i!terin0 pprtu#3 T$i# pro-e## /# done t/i-e nd t$e 'i!tered #o!ution /# emptied into /#te be%er be'ore t$e 'in! rin#e3 T$e be%er -ontinin0 pre-ipitte /# t$en rin#ed into t$e -ru-ib!e on-e more /it$ t$e reminin0 HNO3 T$i# 'i!tered #o!ution /# t$en mo2ed into #m!! te#t tube* nd te#ted 'or -omp!etene## by TA3 T$e #o!ution te#ted po#iti2e 'or -omp!etion nd !-% o' #i!2er ion#3 T$e pre-ipitte /# t$en /#$ed t/i-e /it$ m! #1uirt# o' -etone3 T$e -ru-ib!e /# t$en p!-ed in de#i--tor nd t%en to TA /$o p!-ed t$e -ru-ib!e in J de0ree o2en3 A'ter + minute#* t$e -ru-ib!e /# remo2ed nd m##ed !on0 /it$ t$e pre-ipitte # +3(,.03 T$i# e4periment /# done t/i-e #ide by #ide in order to -ompre re#u!t#3 7
Ob#er2tion#: Smp!e ID: Smp!e De#-ription Smp!e
Comp!etene## o' pre-ipittion
HNO 5#$in0
5$ite po/dery Te#ted po#iti2e 'or 5#$in0 #ub#tn-e /it$ 'ine -omp!ete per'ormed t/i-e* -ry#t!# pre-ipittion /#$in0# te#tin0 po#iti2e 'or
&re-ipitte De#-ription &re-ipitte /# #!i0$t!y purp!e po/dery #ub#tn-e3
-omp!etion3 No 2i#ib!e prti-!e# remined3 &rtner #mp!e
5$ite po/dery Te#ted po#iti2e 'or 5#$in0 #ub#tn-e /it$ 'ine -omp!ete per'ormed t/i-e* -ry#t!# pre-ipittion /#$in0# te#tin0 po#iti2e 'or -omp!etion3 No 2i#ib!e prti-!e# remined3
&re-ipitte /# #!i0$t!y purp!e po/dery #ub#tn-e3
Dt: V!ue#
&rtner# V!ue#
True V!ue C!7 by 5ei0$t
3.
3.
Smp!e M##
,3(+ 87 3,,,( 0
3(+). 87 3,,,( 0
Re1uired A0NO
+.3 87 3,+ m!
+.3) 87 3,+ m!
Cru-ib!e M##
(3) 87 3,,,(0
(3( 87 3,,,( 0
O2en Temperture
J3, 87 3+ de0ree# Ce!-iu#
J3, 87 3+ de0ree# Ce!#iu#
Time pre-ipitte in o2en
+ minute#
+ minute#
&re-ipitte -oo!in0 time
minute#
minute#
M## Cru-ib!e /it$ &re-ipitte
+3(,. 87 3,,,(0
+3+)+ 0 87 3,,,( 0
M## &re-ipitte
(+3J) 87 3,,,+0
(+3J( 0 87 3,,,+ 0
M## C!7
3(J 0 87 .3 4 (,7
3(J 0 87 +3 4 (,7
C!7 by 5ei0$t
+(J3J 87 3,
+,J3(87 3,
A2er0e C!7 by /ei0$t o' t/o tri!#
+(+3 87 3,
+(+3 87 3,
Error
..J)3(
...3.
A20 Error
.((3)
.((3)
Re!ti2e Spred
3) ppt
3) ppt
C!-u!tion#: Calculating required AgNO 3:
From equation (1) in theory, ratio Ag to Cl has 1 to 1 molar ratio. Assuming the sample is 55% chloride by weight (sample mass)(55% chloride by mass) ! g Cl " Smp!e (: 93(+ 87 3,,,( 093 ; 3,)+. 87 3,,,( 0 C!7
&rtner=# #mp!e: 93(+).0 87 3,,,( 093; 3,)+ 873,,,( 0 C!7 Con#ert grams o$ Cl " to moles " " (g Cl )(gmol Cl ) ! moles Cl "
Smp!e (: 93,)+. 87 3,,,( 093 0mo! ; 3,,(,) 87 +3(4 (,7) mo!e# C!7 &rtner=# #mp!e: 93,)+ 87 3,,,( 093 0mo! ; 3,,(, 87 +3( 4 (,7) mo!e# C!7 & o$ mols Cl " ! & o$ moles Ag ' , so con#ert moles to ml. (& o$ moles Ag ' )(moleslitre Ag* )(1+++ ml) ! ml Ag* Smp!e (: 993,,(,) 87 +3(4(,7) mo!e#93(, mo!e#!itre9(,,, m!Litre ; (3 87 3,+ m! A0NO 8 m! e4-e## ; +.3 87 ,3,+ m! A0NO &rtner=# Smp!e: 993,,(, 87 +3(4(,7) mo!e#93(, mo!e#Litre9(,,, m!Litre; (3) 87 3,+ m! A0NO 8 m! e4-e## ; +.3) 87 ,3,+ m! A0NO Calculating mass Cl from mass precipitate:
Con#ert mass precipitate (AgCl (s) ) to moles (mass precipitate (g))(gmol AgCl) ! moles AgCl Smp!e (: 9(+3J) 87 3,,,+ 09(.3+ 0mo! ; 3,+, 87 (3.,4(,7) mo!e# A0C! &rtner=# #mp!e: 9(+3J( 87 3,,,+ 09(.3+ 0mo! ; 3,++J),+) 87 (3.,4(,7) mo!e# A0C! -ecause molar ratio o$ AgCl to Cl " is 1 to 1, con#ert moles Cl " to g " " (& o$ moles Cl )(gmol Cl )! g Cl " Smp!e (: 93,+, 87 (3.,4(,7) mo!e#93 0mo!; 3(J 87 .3 4 (,7 0 C!7 &rtner=# #mp!e: 93,++J),+) 87 (3., 4 (, 7) mo!e#93 0mo! ;3(J 87 .3 4 (,7 0 C!7 Calculating sample Cl ! by "eight: " ((ass Cl )(ass /n0nown alt ample))21++ ! Cl " % by 3eight o$ sample
Smp!e (: 993(J 87 .3 4 (, 7 093(+ 87 3,,,( 04(,, ; +(J3J 87 3, C!7 by 5ei0$t &rtner=# Smp!e: 993(J 87 .3 4 (, 7 93(+). 87 3,,,( 04(,,; +,J3( 87 3, C!7 by 5ei0$t Calculating Average of #rials
(4alue 1 ' 4alue ) ! a#g 9+(J3J 87 3, 8 +,J3( 87 3, + ; +(+3 87 ,
Calculating ! $ncertainty:
% uncertainty ! ((/ncertainty in #alue)(#alue))21++ 93,,,+ 03(J 04(,, ; )3( 4 (, 7 Calculating ! %rror:
% 6rror! ((Calculated 4alue 7 8rue 4alue)(8rue 4alue))21++ Smp!e (: 99+(J3J 7 .3.9.3.4(,, ; .+,3J Error &rtner=# #mp!e: 99+,J3( 7 .3.9.3.4(,,; .,+3( Error A2er0e: 9.+,3J8.,+3(+; .((3) Calculating &elative Spread:
9elati#e spread ! (((:igh Cl " 4alue) 7 (ow Cl " 4alue))(a#g))21+++ parts per thousand 9+(J3J 7 +,J3(9+(+3; 3) ppt
Di#-u##ion: T$e e4periment yie!ded impo##ib!y $i0$ re#u!t#3 T$e m##i2e error i# be!ie2ed to be -u#ed by n error in m##in0 t$e t$e -ru-ib!e# u#ed3 T$e #-!e /# not proper!y -!ibrted 'ter /ei0$in0 t$e un%no/n #mp!e by di''eren-e -u#in0 t$e m## o ' -ru-ib!e# to be re-orded # mu-$ to !o/3 T$i# -u#ed t$e /ei0$in0 by di''eren-e o' t$e pre-ipitte to re#u!t in n e4treme!y $i0$ m##* t$ro/in0 o'' -!-u!tion# t$rou0$out3 6y -ompri#on* t$e -ru-ib!e# o' -o!!e0ue# /ei0$ed #i0ni'i-nt!y more t$n t$o#e u#ed 'or t$i# e4periment3 Hd t$e re#u!t# been $i0$ /it$in re#onb!e error* t$i# -ou!d $2e been -u#ed by ot$er re#on#3 T$e u#e o' too mu-$ e4-e## A08 /$en te#tin0 'or -omp!etion -ou!d $2e !!o/ed 'or t$e 'ormtion o' pre-ipitte /it$ pre#ent ion# ot$er t$n t$e C!7 ion3 Improper /#$in0 o' t$e pre-ipitte my $2e !#o !!o/ed #ome o' t$e un/nted ion# to remin in t$e pre-ipitte3 Con-!u#ion#: T$e #mp!e number /# /it$ true C!7 by /ei0$t o' .3.3 T$e -!-u!ted 2er0e o' C!7 by /ei0$t /# +(+3 87 3, /it$ -!-u!ted un-ertinty o' )3( 4 (,7 3 T$e 2er0e error 9or --ur-y o' t$e e4periment bet/een t$e -!-u!ted 2!ue nd t$e re! 2!ue /# .((3)3 T$e pre-i#ion o' t$e e4periment /# 0ood* $2in0 re!ti2e #pred o' 3) ppt bet/een t$e t/o tri!#3 6ib!io0rp$y: Ar-$er D35* 6ur% R3C* 5o!'' &3A* CHEM ((,(: C$emi#try 'or En0ineer#* Lbortory Mnu! +,((7+,(+* Deprtment o' C$emi#try* Cr!eton* Ott/* .(* 7).3
