Answer to Question #73765 in Inorganic Chemistry for waqar

Question #73765
1) what are main type of edta titration?
2) how the interference of trace of copper in edta titration?
3) name another indicator which can be used instead of EBT as indicator
4) differentiate between subtitution edta titration and acid base EDTA titration
1
Expert's answer
2018-02-21T04:52:38-0500
1) what are main type of edta titration?

1. Direct Titration
In direct titration, you simply add an indicator to the solution of the metal ion and titrate with EDTA. Before starting the titration,it is needed to check that the pH of the solution to obtain a good formation constant value and on the other hand indicator colour change as well.

2.Indiract titration
EDTA can be used as titrant for anions. Anions can be precipitated with suitable metal ion. Filter and wash the ppt with proper solution. Then boil in excess EDTA to complex metal ion(ppt). Back titrate to determine how much metal ion you had.

3.Back Titration
In a back titration an excess of EDTA is added to the metal ion solution, and the excess EDTA is titrated with a known concentration of a second metal ion. The second metal ion must form a weaker complex with EDTA than the analyte ion so the second metal does not displace the analyte ion from its complex with EDTA.

4.Displacement titration

Here the analyte is treated with an excess of a second metal bound to EDTA. The analyte ion displaces the second metal from the EDTA complex, and then the second metal is titrated with EDTA.

2) how the interference of trace of copper in edta titration?

Copper(II) ions can be determined quantitatively by complexometric direct

titration with EDTA in ammoniacal solution. The indicator used is Murexide indicator which is purple when it is free (H4ln-) and yellow (green) when complexed with copper. It should be noted that this method is only applicable to solutions containing up to 25 mg copper ions in 100 mL of water; if the concentration of Cu2+ ions is too high, the intense blue color of the copper(II) ammine complex masks the colour change at the end point. The indicator solution must be freshly prepared. The copper-murexide complex is pure yellow, but the color at the starting point of the titration is greenish depending on the amount of copper present. The green is the mixture of yellow (indicator complex) and blue (copper ions).

3) name another indicator which can be used instead of EBT as indicator.

Indicator murexid can be used instead of EBT, because it is also a complexometric indicator.

4) differentiate between subtitution edta titration and acid base EDTA titration.

Replacement or substitution titration may be used for metal ions that do not react (or react unsatisfactorily) with a metal indicator, or for metal ions which form EDTA complexes that are more stable than those of other metals such as magnesium and calcium.

In acid-base titrations, solutions of alkali are titrated against standard acid solutions. Ostwald developed a theory of acid base indicators which gives an explanation for the colour change with change in pH. According to this theory, a hydrogen ion indicator is a weak organic acid or base. The undissociated molecule will have one colour and the ion formed by its dissociation will have a different colour.

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