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15.2.14

Determine of Copper (ii) ions by EDTA titration


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
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.

determination of copper by edta titration determination of copper by complexometric titration

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