Determine of Copper (ii) ions by EDTA titration

Determine of Copper (ii) ions by EDTA titration

  5:04 PM    Unknown

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how can you determine of copper (ii) ion  concentration ?

in this post we answer on this question by explain the method of EDTA titration that is used to determination of copper cu2+ by complexometric titration

Determination of Copper: Direct Titration using Murexide as indicator

PRINCIPLE:

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 l00mL 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).

REAGENTS:

   1- Copper(II) ions solution (analyte)

   2- Ammonia solution (1:1) as a buffer pH <9

   3- Murexide indicator 

   4- 0.01 M EDTA solution

PROCEDURE:

1- Pipette 25.0 mL of Copper ions solution into a 250.0 mL and add Add

ammonia solution drop-wise until the light blur precipitate first formed

dissolves to form a clear blue solution and dilute to about 100.0 mL with

distilled water.

2- Add 3 to 4 drops of Murixide indicator.

3- Titrate with 0.01 M EDTA until the color changes from yellow (green) to

purpule. Record the used volume (as VEDTA).

4- Repeat the titration twice.

Atomic weight of copper = 63.55 g/mol