GROUP 3

Question 1

slightly soluble sulfides so they can be precipitated by adding basic H25 solution

Answer 1

Group 3

Question 2

give group 3 reagents

Answer 2

Al3+
Cr3+
Fe3+
Zn2+
Ni2+
Co2+
Mn3+

Question 2

Place 1 mL each of the following aqueous solutions to separate centrifuge tube:

Answer 2

Cr(NO3)3
Al(NO3)3
Co(NO3)2
Zn(NO3)2

0.1 M LAHAT

Question 3

Make solution basic by adding

Answer 3

2 mL of 6M NaOH using litmus paper

Question 3

add ___ of ___ and slowly stir for ___ . Then warm in the water bath for ___. record you observations

Answer 3

15-18 ; fresh 3% H2O2 : 1 minute ; 5 minutes

Question 4

After heating the mixtures, add __ drops of __. Boil the mixtures again for __ . After, ___

Answer 4

add 16 drops of 6M NH3 ; 2 minutes ; After let it cool and centrifuge

Question 4

If solid residues are formed

Answer 4

discard the supernatant liquid

Question 5

For those tubes with no solid residues

Answer 5

save the supernatant liquid for further analysis

Question 5

To the centrifuge containing Al+3 , Zn+2 and Cr+3, slowly add few drops of ___

Answer 5

6M acetic acid to solution until it is acidic (test with blue litmus paper)

Question 6

Add concentrated ___one drop at a time until the solution just becomes ______

Answer 6

NH3 ; basic again (test with red litmus paper)

Question 7

Then, add additional drop of excess ___ . Stir the mixture for about a minute to allow the system to reach equilibrium.

Answer 7

Nh3

Question 7

Warm the mixtures in a water bath for ___. Decant the supernatant liquid if there is a ___

Answer 7

5 minutes : precipitate produced

Question 8

To the precipitate containing Al3+, wash the collected solid with ___

Answer 8

6 mL DI water

Question 8

Then, pace the tube in a hot water bath for about ___ occasionally stirring the mixture

Answer 8

2 minutes

Question 8

After, decant the supernatant solution and the precipitate. To the precipitate add ____ and ___

Answer 8

4 drops of 6M CH3COOH and 6mL of DI water

Question 9

Stir in order to dissolve the solid. Finally add ___ of ___ and observe

Answer 9

4 drops of catechol violet to the resulting solution

Question 10

To the centrifuge tube containing Cr+3 ____

Answer 10

add 12 drops of 1M BaCl2

Question 10

To the solution containing Zn+2 ___

Answer 10

acidify with a few drops of 6M CH3COOH and add 3-5 drops of (NH4)2S

Question 10

To the remaining precipitates obtained from procedure 3 that contain ____, wash the precipitate with hot DI water and discard the liquid

Answer 10

Fe+3
Mn+2
Ni+2
Co+2

Question 11

To the precipitates add ___

Answer 11

10 drops 6M HCl and 4 drops of HNO3

Question 12

after the water bath, add __

Answer 12

conc. aq NH3 dropwise until solution is basic and use red litmuss to confirm