Test for Nickel Ni +2
Overview:
The nickel radical is among the fourth group of basic radicals in which
ammonium chloride, ammonium hydroxide and ammonium sulfide are used
as a group reagents.
In this experiment, the solubility of the salt in water will be tested then
reaction of the salt with ammonium sulfide, ammonium chloride and
ammonium hydroxide then confirmatory tests will be performed with
sodium hydroxide, ammonia Solution, potassium cyanide and
dimethylglyoxime.
Aim:
To test for the nickel radical in inorganic salts.
Learning Objectives:
· To study chemical and nature characteristic of nickel.
· Understand various tests to identify the radical presence in a given salt.
· Understand the chemical reactions and their balanced equations that take
place during each test.
· Acquire the skills to perform the experiment in the real lab once they
understand the different steps in the procedure.
Tools:
· Nickel chloride salt NiCl2.
· Ammonium chloride NH4Cl.
· Ammonium hydroxide NH4OH.
· Ammonium sulfide (NH4)2S.
· Sodium hydroxide solution NaOH.
· Ammonia solution NH4OH.
· Potassium cyanide KCN.
· Dimethylglyoxime C4H8O2N2.
· Test tubes.
· Distilled water.
· Spatula.
Steps:
Step 1:
Select Nickel Chloride salt NiCl2 from the table of salts.
Observation: The salt is in a form of yellow powder.
Step 2: (Solubility Test):
Put a small amount of salt in a test tube by spatula then add (1-2) ml of
water then shake the test tube well then heat the test tube on the Bunsen
flame.
Observation: The salt is soluble in hot water.
Step 3: (Ammonia Sulfide test):
Put a small amount of the salt in a test tube by spatula then add drops of
ammonium chloride, ammonium hydroxide and ammonium sulfide
(NH4Cl, NH4OH & (NH4)2S).
Observation: Black precipitate is formed.
Result: Black precipitate of nickel sulfide is formed.
Step 4: (Sodium Hydroxide Test):
Put a small amount of salt in a test tube using spatula then add (1-2) ml of
water then shake the test tube well then heat the test tube on the Bunsen
flame then add drops of confirmatory test reagent sodium hydroxide.
Observation: Green precipitate is formed.
Add more sodium hydroxide to the precipitate.
Observation: The precipitate is not soluble in excess of sodium hydroxide.
Result: Green precipitate of nickel hydroxide which is not soluble in excess
of reagent.
Step 5: (Ammonia Solution Test):
Put a small amount of salt in a test tube using spatula then add (1-2) ml of
water then shake the test tube well then heat the test tube on the Bunsen
flame then add drops of confirmatory test reagent ammonia solution.
Observation: Green precipitate is formed.
Add more ammonia solution to the precipitate.
Observation: The precipitate is soluble in excess of ammonia.
Result: green precipitate of basic salt which is soluble in excess of the
reagent forming complex nickel amine compound.
NiCl2 + NH3 + H2O → Ni(OH)Cl + NH4Cl
Ni(OH)Cl + 7 NH3 + H2O → [ Ni(NH3)6 ](OH)2 + NH4Cl
Step 6: (Potassium cyanide Test):
Put a small amount of salt in a test tube using spatula then add (1-2) ml of
water then shake the test tube well then heat the test tube on the Bunsen
flame then add drops of confirmatory test reagent Potassium cyanide.
Observation: Green precipitate is formed.
Result: green precipitate of nickel cyanide is formed which is readily soluble
in excess of the reagent.
NiCl2 + 2KCN → Ni(CN)2 + 2KCl
Step 7: (Dimethylglyoxime Test):
Put a small amount of salt in a test tube using spatula then add (1-2) ml of
water then shake the test tube well then heat the test tube on the Bunsen
flame then add drops of confirmatory test reagent Dimethylglyoxime.
Observation: Red precipitate is formed.
Result: red precipitate of nickel dimethylglyoxime is formed.
Conclusion:
The basic radical of the salt is Nickel (Ni+2).