Ttrasi Kompleksometri Complexometric Titration：titrasi kompleksometri络合滴定法

1、complexometric titrationsmk negeri 13 bandungcomplexometric titrationvreaction result is complex substancevcommon standard solution : edta (ethylene diamine tetra acetic acid ) what is complex substance?va substance formed by covalent coordination bond;va bonding formed by pair electrons sharing, wh

2、ile the source of pair electrons is only one atom/group.the covalent coordinate in a complex substancevbetween the center atom (metal ion) and the ligand (ion/atom/group that give the pair electrons).vcenter atom give the orbital.vligand give the pair electrons.complex stabilityvif mn+ + lx- mln-x v

3、while mln-x is complex substance thenv mlvk = - is kstabv m lvkstab= stability constantthe more stable the substance will has bigger kstabthe complex is difficult to dissociated to be its ions(compare with weak acid or base)edta(ethylene diamine tetra acetic acid)vligand that have 6 pairs of electro

4、n.vother name : trilon b, complexon iii, sequestrene, versene dan chelaton 3.vrelease 2 h+ from 2 carboxylic.vmost available in disodium salt form.vwrote as h2y=edta concentration always termed in molar, because vedta has 6 electrons pair which could be used in covalent coordinate bond one-by-one.ve

5、dta reacts with any metal with mole ratio 1 : 1.reactionsvm2+ + h2y= my= + 2h+vm3+ + h2y= my- + 2h+vm4+ + h2y= my + 2h+vm5+ + h2y= my+ + 2h+vmn+ + h2y= my(n-4) + 2h+v ph influence to metal-edta complex stabilityvevery reaction of metal ion with edta resulted h+vas le chatelier, if h+ increased, the

6、equilibrium goes to the left (ions)meansvat low ph or high h+ , the stability of metal-edta is decreased.some of kstab of metal-edtav2+ ions 3+ ionsvmg8.7al16.3vca10.7fe25.1vsr8.6y18.2vba7.8cr24.0vmn13.8ce15.9vfe14.3la15.7vco16.3lu20.0vni18.6se23.1the equivalence point detectionvinstrumental : spect

7、rophotometric, amperometric, conductimetric or potentiometricvconventional : using indicator vindicator available: metal ion indicator (metalochromic indicator)vthis indicator is sensitive to very low concentration of metal ion (pm)metal ion indicatorvligand in the form of organic ion which its free

8、 ion colour differ from its complex. vcould also function as indicator ph.vits colour change depend on the ph ( owning typical ph job).vcomplex metal-indicator own the kstab expressed by kin. criterion of choosing indicatorvfor choosing the metal ion indicator, we have to know:v1. ph work indicator.

9、 v2. ph titration ( barbed with the nature of metal ion and metal complex stability edta. vmetal stability edta must metal indicatorsome of metal ion indicators.vebt (eriochrome black t)/solochrome black t/wdfavmurexidvxylenol orangevpyrocathecol violetvbromopyrogalol redvvariamin blue bebt (eriochr

10、ome black t) solochrome black t / wdfavat ph 11.5 yellowish-orange (d3-).vat ph 7-11 reacting with the metal ion. m+ + hd=(blue) md- (red)+ h+preparation of ebt solution.v0.2 gram ebt dissolved in 15 ml three ethanol amine and 5 ml alcohol absolute. vthis solution is stable for a few months. v0.4 gr

11、am ebt dissolved in 100 ml methanol, stable at least 1 month.v1 gram of ebt attenuated with 200 - 500 gram of kcl or nacl or k2so4 or na2so4 . most stable during carried through to run dry in bottle call a meeting to order.murexidevuntil ph 9 reddish violet (h4d-)vph 9 -11 violet (h3d=)vabove ph 11

12、blue-violet or blue (h2d3-)vat ph basevni-murexide, co-murexide yellowvcu-murexide orangevca-murexide redpreparation of murexide solution. v0.5 g of the powdered dyestuff in water, shaking thoroughly, and allowing the undissolved portion to settle. this solution can only be used on making of. everyd

13、ay the old supernatant liquid is decanted and the residue treated with water as before, to provide a fresh solution of the indicator.v 1 g murexide attenuated with 500 gram pure nacl, most stable.xylenol orangevthe indicator at acid ph (1 5) is coloured lemon yellow.vxo metal at acid ph is intensely

14、 red.vtitration is generally conducted at ph 1-3, titration at ph 5 conditioned by hexamine. v0.5 % xo solution in water, most stable.types of complexometric titrationsv1. direct titration.vthe solution containing the metal ion to be determined is buffered to the desired ph (e.g. to ph = 10 with nh:

15、-aq. nh,) and titrated directly with the standard edta solution. it may be necessary to prevent precipitation of the hydroxide of the metal (or a basic salt) by the addition of some auxiliary complexion agent, such as tartrate or citrate or triethanolamine.2. back titration.vmetal ion reacted by exc

16、essive edta, then at certain ph, the excess of edta titrated with the standard metal ion solution such as mgso4 or znso4.vat equivalence point obtained mmol of the rest of edta = mmol metal std, so that countable.vmmol metal ion = mmol (edta metal std).why these types of titrations are selected.v1.

17、metal ion precipitated at ph titration.v2. its complex forming is too slow. v3. there are not appropriate metal ion indicators ( complex stability of metal indicators are ineligible).vend point determined with the sensitive metal ion indicator to metal standard.3. substitution titration. v metal ion

18、 titrated by edta with the other metal ion attendance as an aid of determination of the end point ( for example, determination of ca2+ with aid of mg2+). vthe titration is conducted if:v1. metal ion does not react ( or its reaction dissatisfactory) with indicator, or v2. complexion of metal edta more stable than other.examples:vstability of ca edtamg edtavstability of ca ebtca edtavhence titration ca by ebt have to entangle