Titrations Terminology Titrant Equivalence Point End Point Indicator Titration error Blank Titration Primary Standard Standardization Direct Titration Back Titration
7.7 How many m o! ".#"" $ %I are needed to react wit& '"." m o! "."'"" $ Hg ()*+,-( i! t&e reaction is Hg(( (I/ 0 Hg (I()s)'"." m-)"."'"" mmol1m- 2 #.3" mmol I/4 5ecause %I is a solu5le salt T&ey react in a #6( mole ratio. )#.3" mmol I/-)# mmol Hg((1( mmol I/-)# m1".#"" mmol- 2 ."" m
7.## ".8'#, g o! 9owdered limestone was dissolved and :+( was e;9elled 5y adding #"."" m o! #.,<3 $ o! H:l. T&e e;cess H:l required ,<.<3 m o! ".#""' $ *a+H. =ind t&e weig&t 9ercent o! calcite ):a:+,- in t&e limestone. :a:+,)s- (H 0 :a( :+()g- H(+ mmoles H reacted 2 >)#"."" m-)#.,<3 $- /),<.<3 m *a+H-)".#""' mmol1m-?2 <.<8 mmol moles o! :a:+, reacted 2 <.<81( 2 '.<7 mmol :a:+, mass "! :a:+, 2 )'.<7 mmol- @)#""."73(- 2 '<7.77< mg wt A 2 )'<7.77<18'#.,-@#"" 2 <(." A
7.#( T&e %elda&l reaction was used to analyze (83 µ o! a solution containing ,7.< mg 9rotein1m. T&e li5erated *H, was collected in 8."" m o! ".",,3 $ H:l4 and t&e remaining acid required 3.,' m o! ".#" $ *a+H !or com9lete neutralization. C&at is t&e weig&t 9ercent o! t&e nitrogen in t&e 9rotein Protein &eat and acid 0 *H' :+()g- H(+ Base is added and ammonium is converted to *H,)g- and t&e gas is collected in a solution containing a known amount o! strong acid. H *H, 0 *H' 4 leaving an e;cess amount o! H. mmoles * 2 >)8.""m-) ".",,3$- /)3.,' m *a+H-)".#" mmol1m-?2 ".#"' 3 mmol mg * 2 )".#"'3 mmol-@)#'.""37 mg1mmol- 2 #.'38 mg * mg 9rotein 2 )".(83 m-@),7.< mg1m- 2 <.7"(' mg 9rotein A * 2 )#.'381<.7"('-@#"" 2 #8.# A 7.#, rsenic o;ide )s(+,- is availa5le in 9ure !orm and is a use!ul 9rimary standard !or o;idizing agents4 suc& as $n+'/. Titration reaction s(+, +H/ F (Hs+,(/ H(+ Hs+,(/ (H 0 H,s+' 8H,s+, ( $n+ '/ 3H 0 8H,s+' ( $n ( ,H(+ a- ,.(#' g o! %$n+' was dissolved in #.""" . C&at is t&e t&eoretical molarity o! t&is solution ),.(#' g-1)#mol1#8.",'-@)#1#.""" - 2 "."(",' $ 5- How muc& s(+, would we e;9ect to react wit& (8."" m o! t&e solution in a)(8.""-)"."(",'-)8 mol H,s+,1( mol $n+'-)#mol s(+,1( mol H,s+'-)#<7.' mg1mmol- 2 #(8.7 mg c- It was !ound t&at ".#'3 g o! s(+, required (<.< m. T&e 5lank required ".", m. :alculate t&e actual concentration o! t&e $n+'/ solution. )#'3. mg-)# mmol1#<7.' mg-)' mol $n+ '/18mol s(+,-@)#1)(<.<m/ ".",m-- 2 "."#<( $
7.#3 :*/ solution wit& a volume o! #(.7, m was treated wit& (8."" m o! *i ( solution to !orm *i):*- '(/. T&e e;cess *i( was titrated wit& #".#8 m o! a "."#,"7 $ solution o! EDT. *i( ':* / 0 *i):*- '(/ *i( EDT'/ 0 *i)EDT- (/ *i):*-'(/ does not react wit& EDT. I! ,<.,8 m is required to titrate ,".#" m o! t&e srcinal *i concentration o! t&e cyanide solution.
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solution4 determine t&e
G*i( 2 ),<.,8 m-)"."#,"7-1,".#" m 2 "."#7"7 $ >)(8."" m-)"."#7"7 $-/)#".#8@"."#,"7-?)' mmol :* /1# mmol *i(-)#1#(.7, m2 "."<(8' $ 7.( mi;ture &aving a volume o! #""." m and containing ".#"" $ g and ".#"" $ Hg(( was titrated wit& ".#""" $ %:* to 9reci9itate Hg ():*-( and g:*. :alculate t&e 9:*/ at eac& o! t&e !ollowing volumes 8.""4 #".""4 #8.""4 #<.<"4 (".#"4 (8.""4 ,".""4 ,8."" m. S&ould any g:* 5e 9reci9itated at #<.<" m 99endi; = %s9)Hg():*-(- 2 8J#"/'" %s9)g:*- 2 (.(J#"/#3
t 8."" m added GHg(( 2 >)#" m-)".#"" $- K )8."" m-)".#"""-)# mmol Hg ((1(mmol :*/-?1#8." m 2 8.""J#"/( $ G:*/ 2 >%s9)Hg():*-(-1GHg((?#1( 2 #.""J#"/#< $ Gg 2 )".#""-)#"1#8- 2 "."337 $ Lg:* 2 GgG:*/ 2 3.37J#"/(# M %s9)g:*-4 t&ere!ore no g:* 9reci9itates 9):*/- 2 /log G:*/ 2 #<.""
t #<.<" m added GHg(( 2 >)#" m-)".#"" $- K )#<.<" m-)".#"""-)# mmol Hg ((1(mmol :*/-?1(<.<" m 2 #.37J#"/' $ G:*/ 2 >%s9)Hg():*-(-1GHg((?#1( 2 #.7,J#"/# $ Gg 2 )".#""-)#"1(<.<"- 2 ".",,' $ Lg:* 2 GgG:*/ 2 8.7J#"/(" M %s9)g:*-4 t&ere!ore no g:* 9reci9itates 9):*/- 2 /log G:*/ 2 #7.73 at (".#" m added4 we are 9ast t&e !irst equivalence4 essentially all o! t&e Hg(( &as 5een e;&austed4 and now g will 9reci9itate as g:*. Gg 2 ))#"m-)".#""- K )(".#"/(".""-).#"""--1,".#" m 2 ".",(< $ G:*/ 2 %s9)g:*-1Gg 2 3.3
t ,"."" m added we &ave reac&ed t&e second equivalence 9oint. Essentially all o! t&e g &as 5een titrated and t&ere is no e;cess G:*/. T&ere!ore4 %s9)g:*- 2 ;(4 w&ere ; 2 G:*/ G:*/ 2 #.'J#"/ $ 9:*/ 2 7., GHg(( 2 %s9)Hg():*-(-1G:*/( 2 (.(7J#"/(' $ t ,8."" m added we &ave gone 8."" m 9ast t&e second equivalence 9oint. G:*/ 2 )".#"""-)8."" m-1),8."" m- 2 #.##J#" /( $ 9:*/ 2 #.<8
[Hg22+] [CN-] 0.00 5.00 5.00E-02 10.00 2.50E-02 15.00 1.00E-02
[Ag+] 1.00E-19 1.41E-19 2.24E-19
Q(AgCN) pCN0.1 6.67E-02 6.67E-21 5.00E-02 7.07E-21 4.00E-02 8.94E-21
19.00 18.85 18.65
19.90 20.10 25.00 30.00 35.00
1.67E-04 1.12E-11 2.11E-12 2.27E-24 4.05E-36
1.73E-18 6.69E-15 1.54E-14 1.48E-08 1.11E-02
3.34E-02 3.29E-02 1.43E-02 1.48E-08 1.98E-14
5.78E-20 2.20E-16 2.20E-16 2.20E-16 2.20E-16
17.76 14.17 13.81 7.83 1.95
7.,3 ,"."" m solution o! I/ was treated wit& 8"."" m o! ".,38 $ g*+,. gI)s- was !iltered o!! and t&e !iltrate )9lus =e,- was titrated wit& ".(7" $ %S:*. C&en ,7.3" m &ad 5een added4 t&e solution turned red. How many mg o! I/ were in t&e srcinal solution T&is is a 5ack titration g S:*/ 0 g)S:*-)s%s9)gS:*- 2 #.#J#"/#( mmol g added 2 )8"."" m-)".,38 $- 2 #.( 8 mmol mmol g reacted wit& S:*/ 2 ),7.3" m-)".(7" $- 2 #".7< # mmol mmol g reacted wit& I/ 2 7.' 3 mmol mmol I/ 2 7.'3 mmol GI/ 2 7.'3 mmol1,"."" m 2 ".(8 $
