I-Ion Exchange Separations: Complexometric Titrations

Dr. Prem D. Sattsangi

Copyright © 2009

Exp.#5 Ion-Exchange Separations of CuCl4

-2, CoCl4-2 complexes

N

CH3

CH3

CH3

+CuCl4

-2

CoCl4-2+

N

CH3

CH3

CH3(Binds less tightly, moves faster)

(Binds MUCH more tightly, moves slower)

AMBERLITE: IRA-400 with Copper and Cobalt complexes

Chloro-Complexes

Dark Purple

#2-Chloro-Complexes, U.K.#9, Volumetric Flasks 1-3

Chloro-Complexes

U.K.Mixture Labeled

#3-Pipetting U.K. mixture in Vol. Flask #1

Use micropipet for the last few mL, avoid over shooting.

1. Pipet 1 mL U.K. 2. Add it to flask 1 3. Make it up to the mark

No need to rinse 1 mL pipet here.

#4-Get Ready with Resin Column

1. Resin column is prepared in 3 M HCl.2. Clamp it securely to a Buret stand.3. Place a 50 mL Beaker underneath.4. Take 50 mL, 3 M HCl in a 50 mL

Graduated Cylinder and a micropipet.

#5-Applying 1 mL sample to the column

(1) (2)Drain

(3)Apply

(4)sides

(5) (6)Drain

(7)Rinse

Use M.P.3M HCl

Apply 1 mL pipet (1” above)Along sides of buretDrain

HCl Flush

Drain Flush

Resin in 3 M HCl

#6-Insert a small wad of cotton on the top. Elute with 3 M HCl.

Notice the Faint Greenish band 11-14 mL region

Add 3 M HCl. Do NOT Over-fill.Keep watch on the Migrating Band.

It grows fainter as it migrates.

Chloro-complexes are changing to aquo- complexes.

#7- Cobalt elutes first. After ~10 mL of 3 M HCl, switch to small test tubes in a rack.

Collect ~ 5 mL in each test

tube. Watch the white glass wool area turn slight pink.

Slight pinkCobalt is coming out.

Tubes 1 and 7 seem to contain NO Cobalt. All these are taken.

#8-Elution of Copper with distilled waterCopper elutes fast.

1. Collect in test tubes to begin with.2. Color on the white glass wool, at the bottom will turn to a faint Blue.3. DW converts Copper(II) to positively charged aquo-complex. 4. It is repelled by the + charge on the resin.

Tubes 1 and 11 seem to contain NO Copper. All these are taken

CuCl4-2 + H2O [Cu(H2O)4]2+

(Repelled)

#9-Transferring the fractions in the test tube to Volumetric 3. Cu+2

1. Place a funnel on the top.2. First pour tubes #2-93. Put tubes back in their place.

4. Use Tube #1 to rinse tubes 2-9

5. Pour tubes 9 and 10 to the flask

#10-Rinse Funnel with DW

(1) Use Squeeze bottle to wash the funnel with DW.

(2) Use 50 mL beaker to add more DW. Do not fill up to the neck.

(3) Use Micropipet to make it up to the mark.

Stopper securely. Shake and store for the next turn.

(1)

(3)(2)

General Advice: Economize, time, resources.

Record everything directly in your note book.

DO NOT WAIT FOR pH meter. APPROXIMATE readings will do.

Washing glass ware:Use cold Tap water. Flush generously. Rinse with DW, using squeeze bottle. Squirt about 5 mL DW along

sides of the flask. Drain excess on a paper towel.

Weighing Murexide:Use the same weighing paper for all the weighings.Approximate 2.2-2.4 g is accurate enough.

After finishing, do not forget to wash generously with ordinary waterthe buret and the pipet, before storing.

#11-Titration of Mixture in Vol. Flask -1

Experiment

Mixture #_____ Cu2+ (H2O)4 and Co2+ (H2O)4

a. Pour ~20 mL of mixture in a Beaker. Rinse the 25.00 mL pipet.

b. Pipette 25mL of Mixture into 2 Erlenmeyer flasks A, and B

c. Adjust pH and make each flask ready for titration.

Observations:

#12-Titration of Mixture in Vol. Flask -1

INSTRUCTIONS:

1. Use pH meter, add 3M NH3 to adjust pH to 9. Repeat the procedure for flask (B).

2. Add 0.2-0.25g of Murexide, to flask “A” swirl. Color (Green - Yellow - Orange). Titrate flask A. Color, at end point, will be ~red.

3. Add Murexide and titrate “B”4. Calculate molarity (M) for Co+2 + Cu+2.

Lab-Notes for Mixture Titrations

OBSERVATIONS:

Color ____________

Color with Murexide ________

Experiment:

Added 3M NH3 ____drs to pH 9. Used pH meter (3M NH3/3MHCl).

Added ______g of Murexide, swirled to mix.

TITRATION OF MIXTURE : Concentration of EDTA_____.Buret readings Set – A Set – B Final ______mL _____mLInitial ______mL _____mLEDTA used ______mL _____mLColor at end point ___________

#13-Calculations

One mole of EDTA reacts with 1 mol of M2+ to form a Chelate complex. EDTA + M2+ M(EDTA)2+

complex

EDTA is ~0.01 M. Copy exact concentration of EDTA from the reagent bottle. EDTA _____M Molar concentration of Co+2 (mL cancels)

  

Molar concentration of Cu+2 (Show calculations same way)  

Molar concentration of Mixture of Co+2 and Cu+2

(Show calculations same way)

22

Co ____M mL 25EDTA mol 1

Co mol 1 ___M EDTA ___mL

#14-Titration of Cobalt(II)

INSTRUCTIONS: (Co2+ (H2O)4)

1. Rinse pipet. Take 25 mL of Co+2 in each flask A and B.

2. Use pH meter. Add 15M NH3 to pH 8-9 light blue/Turquoise color.

3. Add 3M NH3 until pH is 9. Repeat the procedure for flask (B). 4. Add 0.2-0.25g of Murexide to flask A, swirl. Color will be orange. Titrate flasks A to a pinkish red end point. 5. Add Murexide and titrate “B” 6. Calculate molarity (M) for Co2+.

Lab-Notes for Co+2 Titrations

OBSERVATIONS:

Color ____________

Color with Murexide ________

Experiment:

Added 3M NH3 ____drs to pH 9. Used pH meter.Added ______g of Murexide, swirled to mix.

TITRATION OF MIXTURE : Concentration of EDTA_____.Buret readings Set – A Set – B Final ______mL _____mLInitial ______mL _____mLEDTA used ______mL _____mLColor at end point ___________

INSTRUCTIONS: (Cu2+ (H2O)4) 1. Rinse pipet. Take 25 mL of Cu+2 in each

flask A and B.2. Use pH meter. Add 3M NaOH to get a

distinct blue/turquoise color (pH10-12).3. Add few drops of 6M HCl to make the color disappear. 4. Add 3M NH3 until pH is 9-10. Add 10 drops of pH 10 buffer If needed, adjust pH to 10 (3M NaOH) Do the same for Flask “B”.5. Add 0.2-0.25g of Murexide and swirl.

Color will be Yellow/ green.6. Titrate to pinkish red. 7. Add Murexide and titrate “B” 8. Calculate molarity of Cu2+

#15-Titration of Copper(II)

2.

3.

4.

5.

6.

Lab-Notes for Cu+2 Titrations

OBSERVATIONS:

Color ____________

Color with Murexide ________

Experiment:

Added 3M NH3 ____drs to pH 9. Used pH meter.Added ______g of Murexide, swirled to mix.

TITRATION OF MIXTURE DATA: Concentration of EDTA_____.Buret readings Set – A Set – B Final ______mL _____mLInitial ______mL _____mLEDTA used ______mL _____mLColor at end point ___________