Kerropi


Wednesday, June 15, 2011

QUALITATIVE ANALYSIS OF CATIONS

Qualitative Analysis Of Cations

Objectives
Student can differentiate qualitatively a few cations in the lab

Introduction
Qualitative analysis is used to separate and detect cations and anions in a sample substance. there are several solutions containing ionic substances can be chemically analyzed to determine the presence of certain cations. Qualitative analysis based on the use of several chemical tests that can give a clear result for each specific cause of some ions in the solution. The reagent can react with a specific cation and observation of the reaction can be certified if the cation is known and there is no reaction means no specific cation or a cation can also be stated. The study was based on the determination of the ion is more than a few reagents.

Equipment
-Glass tube rack
-Glass Tube
-Dropper
-Self adhesive paper



Reagent

These solution with concentration of 0.1 M of

-Plumbum (II) nitrate, Pb(NO3)2
-Copper (II) Nitrate, Cu(NO3)2
-Iron (III) Nitrate, Fe(NO3)2
-Cobalt (II) Nitrate, Co(NO3)2
-Zinc (II) Nitrate, Zn(NO3)2
-Magenesium (II) Nitrate, Mg(NO3)2
-Barium (II) Nitrate, Ba(NO3)2
-Cation X
-Cation Y

#Sodium Sulphate Solution, Na2SO4, 2M
#Ammonium Sulphide Solution, (NH4)2S, 1M
#Sodium hydroxide solution, NaOH, 4M
#Ammonium tiocianate, NH4SCN, 2M


Procedure :
A) Reaction with sulphate ion, SO4²¯
1. 9 Glass tube was prepared and labeled with a until i
2. The glass tube was filled with 5 ml of distilled water
3. 10 drops of Plumbum (II) nitrate, Pb(NO3)2 solution is added into glass tube A, 10 drops of Copper (II) Nitrate, Cu(NO3)2 solution is added into glass tube b, 10 drops of Iron (III) Nitrate, Fe(NO3)2 solution is added into glass tube C, 10 drops of Cobalt (II) Nitrate, Co(NO3)2  solution is added into glass tube D, 10 drops of Zinc (II) Nitrate, Zn(NO3)2 solution is added into glass tube E, 10 drops of Magenesium (II) Nitrate, Mg(NO3)2 solution is added into glass tube F, 10 drops of Barium (II) Nitrate, Ba(NO3)2
solution is added into glass tube G, 10 drops of Cation X solution is added into glass tube H and 10 drops of Cation Y solution is added into glass tube I.
4. 10 drops of sodium sulphate solution was added in each glass tube and the tube is shaken after adding. Hold for 5 minutes.
5. Observation was recorded.

B) Reaction with suphide ion
1. 9 Glass tube was prepared and labeled with a until i
2. The glass tube was filled with 5 ml of distilled water
3. 10 drops of Plumbum (II) nitrate, Pb(NO3)2 solution is added into glass tube A, 10 drops of Copper (II) Nitrate, Cu(NO3)2 solution is added into glass tube b, 10 drops of Iron (III) Nitrate, Fe(NO3)2 solution is added into glass tube C, 10 drops of Cobalt (II) Nitrate, Co(NO3)2  solution is added into glass tube D, 10 drops of Zinc (II) Nitrate, Zn(NO3)2 solution is added into glass tube E, 10 drops of Magenesium (II) Nitrate, Mg(NO3)2 solution is added into glass tube F, 10 drops of Barium (II) Nitrate, Ba(NO3)2
solution is added into glass tube G, 10 drops of Cation X solution is added into glass tube H and 10 drops of Cation Y solution is added into glass tube I.
4. 10 drops of sodium sulphide solution was added in each glass tube and the tube is shaken after adding. Hold for 5 minutes.
5. Observation was recorded.

C) Reaction with thiocianate ion
1. 9 Glass tube was prepared and labeled with a until i
2. The glass tube was filled with 5 ml of distilled water
3. 10 drops of Plumbum (II) nitrate, Pb(NO3)2 solution is added into glass tube A, 10 drops of Copper (II) Nitrate, Cu(NO3)2 solution is added into glass tube b, 10 drops of Iron (III) Nitrate, Fe(NO3)2 solution is added into glass tube C, 10 drops of Cobalt (II) Nitrate, Co(NO3)2  solution is added into glass tube D, 10 drops of Zinc (II) Nitrate, Zn(NO3)2 solution is added into glass tube E, 10 drops of Magenesium (II) Nitrate, Mg(NO3)2 solution is added into glass tube F, 10 drops of Barium (II) Nitrate, Ba(NO3)2
solution is added into glass tube G, 10 drops of Cation X solution is added into glass tube H and 10 drops of Cation Y solution is added into glass tube I.
4. 10 drops of ammonium thiocianate solution was added in each glass tube and the tube is shaken after adding. Hold for 5 minutes.
5. Observation was recorded.

D) Reaction with hydroxide ion
1. 9 Glass tube was prepared and labeled with a until i
2. The glass tube was filled with 5 ml of distilled water
3. 10 drops of Plumbum (II) nitrate, Pb(NO3)2 solution is added into glass tube A, 10 drops of Copper (II) Nitrate, Cu(NO3)2 solution is added into glass tube b, 10 drops of Iron (III) Nitrate, Fe(NO3)2 solution is added into glass tube C, 10 drops of Cobalt (II) Nitrate, Co(NO3)2  solution is added into glass tube D, 10 drops of Zinc (II) Nitrate, Zn(NO3)2 solution is added into glass tube E, 10 drops of Magenesium (II) Nitrate, Mg(NO3)2 solution is added into glass tube F, 10 drops of Barium (II) Nitrate, Ba(NO3)2
solution is added into glass tube G, 10 drops of Cation X solution is added into glass tube H and 10 drops of Cation Y solution is added into glass tube I.
4. 10 drops of sodium hydroxide was added in each glass tube and the tube is shaken after adding. Hold for 5 minutes.
5. Observation was recorded.




Result
Suphate

Test Tube                 Observation                                         Equation  
A Cloudy solution with white precipitate (Na2SO4 + Pb(NO3)2  -----> PbSO4 + 2NaNO3) 
B Light Blue Cloudy Solution (Na2SO4  + Cu(NO3)2-----> CuSO4 + 2NaNO3)  
C Goldish solution with little orange precipate (Na2SO4 + Fe(NO3)2-----> FeSO4 + 2NaNO3)
D Clear solution (Na2SO4 + Co(NO3)2-----> CoSO4 + 2NaNO3)
E Cloudy solution with white precipitate (Na2SO4 + Zn(NO3)2-----> ZnSO4 + 2NaNO3 )  
F Clear Solution (Na2SO4 +  Mg(NO3)2-----> MgSO4 + 2NaNO3)  
H Cloudy solution with white precipitate (Na2SO4  +  Ba(NO3)2-----> BaSO4 + 2NaNO3)
G Cloudy solution with white precipitate  
I Clear Solution

Sulphide

Test Tube Observation                                         Equation  
A Brown solution with black precipitate  (NH4)2S + Pb(NO3)2-----> 2NH4NO3 + PbS   
B Light yellowish solution with black precipitate (NH4)2S + Cu(NO3)2-----> 2NH4NO3 + Cu  
C Black Solution (NH4)2S + Fe(NO3)2-----> 2NH4NO3 + FeS  
D Black Solution (NH4)2S + Co(NO3)2-----> 2NH4NO3 + CoS  
E Light brown solution with dark brown precipitate (NH4)2S +  Zn(NO3)2-----> 2NH4NO3 + ZnS  
F Colourless solution (NH4)2S +  Mg(NO3)2-----> 2NH4NO3 + MgS  
G Colourless Solution (NH4)2S +  Ba(NO3)2-----> 2NH4NO3 + BaS  
H Light brown solution with dark brown precipitate  
I Colourless solution with white precipitate

Hydroxide

Test Tube Observation Equation  
A Clear Solution 2NaOH + Pb(NO3)2-----> 2NaNO3 + Pb(OH)2  
B Colourless solution with dirty green precipitate 2NaOH + Cu(NO3)2-----> 2NaNO3 + Cu(OH) 
C Colourless solution with brown precipitate 2NaOH +  Fe(NO3)2-----> 2NaNO3 + Fe(OH)2  
D Colourless solution with brown precipitate 2NaOH +  Co(NO3)2-----> 2NaNO3 + Co(OH)2  
E Clear solution 2NaOH +  Zn(NO3)2-----> 2NaNO3 + Zn(OH)2  
F Cloudy 2NaOH +  Mg(NO3)2-----> 2NaNO3 + Mg(OH)2  
G Clear Solution 2NaOH +   Ba(NO3)2-----> 2NaNO3 + Ba(OH)2  
H Clear Solution  
I Clear Solution

Tiocianate

Test Tube Observation Equation  
A Clear Solution 2NH4SCN+  Pb(NO3)2----->2 NH4NO3 + PbSCN  
B Light Green 2NH4SCN +  Cu(NO3)2-----> 2 NH4NO3 + CuSCN  
C Dark brownish 2NH4SCN + Fe(NO3)2-----> 2 NH4NO3 + FeSCN  
D Light Pink  2NH4SCN+  Co(NO3)2-----> 2 NH4NO3 + CoSCN  
E Clear Solution 2NH4SCN +  Zn(NO3)2-----> 2 NH4NO3 + ZnSCN  
F Clear Solution 2NH4SCN +  Mg(NO3)2-----> 2 NH4NO3 + MgSCN  
G Clear Solution 2NH4SCN+   Ba(NO3)2-----> 2 NH4NO3 + BaSCN  
H Clear Solution  
I Clear Solution









Discussion
This experiment shows on how reagents can be used to produce colored solutions or precipitates when certain ions are present.  Using such techniques to determine what components are present in a sample is called qualitative analysis. The cations to be studied include some common alkali metals (Na+ and K+) and some alkaline earth metals (Mg2+, Ca2+, and Ba2+), along with Zn2+, Al3+, and NH4+.  These ions are not colored in solution, and most of their compounds are white.  It is impossible therefore to use colors of solutions or precipitates to indicate which of these cations is present in solution.  So, in this experiment, will use differences in solubilities to separate the cations from each other.  Na+, K+, and NH4+ ions form very few insoluble compounds. All the sulfates of the cations listed above are all soluble, with the exception of barium sulfate.  Calcium sulfate is slightly soluble and will not precipitate under the conditions of this experiment.  Thus adding sulfate to a mixture of these cations will allow to detect barium and remove it from solution. Four of the other cations form insoluble hydroxides. (Calcium hydroxide is slightly soluble, but will precipitate in a strongly basic solution.)  Two of these, however, are amphoteric and will dissolve in a strongly basic solution to form complex ion. By making the solution strongly basic, then, two of the remaining cations will precipitate, while two more will be converted to complex ions.  The two which precipitate can be separated due to differences in the solubilities of their oxalates.  One of them will precipitate when ammonium oxalate is added. The solution containing the complex ions will then be acidified, then neutralized with NH3(aq).  In this weakly basic solution one of the amphoteric hydroxides will precipitate, while the other forms a complex ion with NH3(aq).  Finally, this last cation is precipitated with sulfide ion.

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