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