Complexometry Determination of Cr III and Iron III in a Mixture Kinetic Masking

COMPLEXOMETRY  Determination of Cr (III) and Iron (III) in a Mixture – ineti! Ma"#in$ CEMICAL E*'ATI&%S, PRI%CIPLE I%V&LVED PR&CED'RE Rea"on" for Imortant Ste" C&MP'TATI&%S I%V&LVED Reaction+ Reaction+ Com Come exa xati tion on Pa!e 1/ mL of t9e "oution !ontainin$ 7=T9i" titration "er8e" a" a 47in71 titration rea!tion t9e t5o meta" (!on!entration of for 4 ion" neit9er ex!eed" /0/1 M) in a // mL Fe3> Titration: Re"idua  Titration Indicator: -.eno &ran$e Diute to 1// mL 5it9 deioni;ed Excess Excess Titran Titrant: t: /0/1M Cr3> 7=Deioni;ed 5ater i" u"ed to re8ent EDTA interferen!e interferen!e from ot9er meta ion"0 Back Titrant: /0/1M Add 4/ mL of "tandard EDTA P2(%&3)4 "oution P24> Endpoint: Endpoint: emon .eo56 7=EDTA form" a !omex 5it9 Fe , 2ut not red78ioet 5it9 Cr  due to di:eren!e" in t9e rate of Cr

3>

3>

Add 9examine to adu"t t9e  to

Titration Conditions: Fe !od and a!idi! (ex!e"" EDTA) Cr  2oied and a!idi! (ex!e"" EDTA) Pb "i$9t. a!idi! (2a!#) 3+

3+

formation of t9eir re"e!ti8e !omexe" 5it9 EDTA0 T9e Fe (III)7EDTA !omex form" raid. in !od "oution"0

Fe (III) !ontent (V EDTA and VP2%&3 are from 1"t addition)+

-

-

2+

-

Kinetic Masking 7 a !a"e in 59i!9 a meta

ion doe" not not e:e! e:e!ti ti8e 8e. . ente enterr into into t9e t9e !omexatio !omexation n rea!tion rea!tion 2e!au"e 2e!au"e of  it" #ineti! inertne"" 7 di:eren!e in rate" of rea!tion 5it9 EDTA EDTA of meta !ation" are utii;ed <
7=examine "er8e" a" a 2u:er0

Add a fe5 dro" of t9e indi!ator "oution and titrate t9e ex!e"" EDTA 5it9 t9e "tandard ead nitrate "oution to t9e formation

 To  To t9e re"utin$ "oution, "oution, add a 4/ mL ortion of "tandard EDTA EDTA "oution0 Add nitri! a!id (1 M) to adu"t  to 174 and 2oi t9e

Coo, diute to // mL u"in$ deioni;ed 5ater, and add 9examine to  B70 Add more of t9e indi!ator "oution and titrate ex!e"" EDTA 5it9 t9e "tandard ead nitrate "oution0 <
%Fe 3 + ¿

7=-.eno oran$e i" u"ed a" t9e indi!ator "in!e it i" "ta2e in an a!idi! medium0 It i" a"o u"ed "in!e it i" "e!i?! for Fe 3> and Cr3> at t9e "e!i?ed  and temerature0 P2%&3 i" u"ed a" t9e 2a!#7titrant "in!e t9e P27EDTA !omex 9a" a o5er "ta2iit. !on"tant (1@0/) !omared to t9e Fe (III)7 EDTA !omex (4B01/)0

7=T9i" ortion of EDTA rea!t" 5it9 Cr3>0 oiin$ i" done to in!rea"e t9e rate of formation of t9e Cr (III)7EDTA !omex0

 MEDTA x VEDTA VEDTA )  [ ( MEDTA

Cr (III) !ontent (V EDTA and VP2%&3 are from 4nd addition)+

 MEDTA x VEDTA VEDTA ) [ ( MEDTA
REFERE%CES+

7=T9e 7=T9e P27EDT P27EDTA A 9a" a o5er o5er "ta2i "ta2iit. it. !on"tant !omared to Cr (III)7EDTA (430)0

C9ri"tian, H0D0 (4//) Analytical (4//) Analytical Chemistry (t9 ed) 'SA+ o9n Jie. and Son",   In!0 ar8e., D0 (4///) Modern Analytical Chemistry (1"t ed) '"a+ M!Hra57i Comanie", In!0  e:er., H0 0, a""ett, 0, Mend9am, 0 and Denne., R0 C0 (1G@G)0 Vogel's Textbook of !antitati"e Chemical Analysis# (Bt9 Analysis# (Bt9 ed0)0 En$and+ Lon$man S!ienti?! K Te!9ni!a0 0 33B M!P9er"on, P0A0C0 (4/1B)0 Practical Vol!metric Analysis0 Analysis 0 Cam2rid e+

DEMATA, ESTEVES, FELIPE, FELIZARTE