ANALYSIS OF SALT 2 ( Ammonium chloride)
Experiment : - TO ANALYSE THE GIVEN SALT FOR ACIDIC RADICAL (ANION) AND BASIC RADICAL (CATION)
Theory : Two basic principles are used (i) solubility product and (ii) common ion effect.
When ionic product of a salt exceeds its solubility product, precipitation takes place and ionic product of a salt is controlled by making use of common ion effect.
Materials required: Test tubes, test tube stand, test tube holder, filter paper, watch glass, glass rod, burner, tripod stand, wire gauze, beakers, nickel spatula, reagents etc.
Sl. No. | EXPERIMENT | OBSERVATION | INFERENCE |
A) PRELIMINARY TESTS |
1. | PHYSICAL EXAMINATION |
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a) | Colour of the salt noted | White coloured
| absence of Cu 2+ , Fe 2+, Fe 3+, Ni 2+, Co2+, Mn2+ ions
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b) | Smell noted : - a lilltle of the salt is rubbed between fingers with a drop of water. | ammoniacal smell
| ammonium NH4+ salt may be present CHEMISTRY :- On rubbing the ammonium salt liberates ammonia gas
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2. | DRY HEATING TEST A small amount of the salt is heated in a dry test tube. | ammoniacal smell and while sublimate formed on the walls of the test tube also
| ammonium NH4+salt may be present. It may be ammonium chloride since ammonium chloride is sublimable CHEMISTRY :- On heating the ammonium salt liberates ammonia gas
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3. | FLAME TEST A little of the salt is made into a paste with conc.HCl in a watch glass and shown to the non luminous part of the flame using a glass rod. | no characteristic reaction | absence of calcium, barium, strontium or copper ions |
4. | COBALT NITRATE TEST/ASH TEST To a little of the salt solution a few drops of conc. HNO3 and a few drops of cobalt nitrate solution is added in a test tube, heat the solution, dip a filter paper into the solution and burnt into ashes | no characteristic coloured ash | absence of zinc, magnesium, aluminium ions |
B) IDENTIFICATION TEST FOR ANIONS |
1. | DILUTE SULPHURIC ACID TEST A little of the salt is treated with 1-2ml of dil. H2SO4 | no characteristic reaction | absence of carbonate |
2. | CONC. SULPHURIC ACID TEST i) To a little of the salt conc. H2SO4 is added and warmed if necessary
| colourless pungent smelling gas is evolved which gives white fumes when a glass rod dipped in NH4OH solution is shown on its mouth. | Presence of chloride CHEMISTRY Cl- + H2SO4→ HSO4- + HCl↑ (colourless pungent gas) HCl + NH4OH → NH4Cl (white fumes) + H2O
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3. | TEST FOR SULPHATE:- BaCl2 test:- A little of the salt solution is added with few drops of BaCl2 solution and conc. HCl is added to it | no characteristic reaction | Absence of sulphate |
C CONFIRMATORY TEST FOR ANIONS
PREPARATION OF WATER EXTRACT FOR SOLUBLE SALTS :- Two nickel spatula full of salt is dissolved in 10ml distilled water in a test tube.
CONFIRMATORY TEST FOR CHLORIDE |
1. AgNO3 test :- To a little of the water extract add Dil HNO3 , add few drops of . AgNO3 and warmed if necessary
2.Chromyl chloride test:- a)Mix a small amount of salt with a small amount of K2Cr2O7 in a test tube and add few drops of conc. H2SO4 b) Heat if needed and pass the orange red vapours into NaOH solution kept in another test tube. c) To the yellow solution obtained add dil. Acetic acid and lead acetate solution | White ppt which is soluble in ammonium hydroxide
A yellow ppt is formed
| Presence of chloride is confirmed CHEMISTRY Cl- + AgNO3→AgCl(white ppt) + NO3- AgCl + 2 NH4OH → [Ag(NH3)2]Cl(soluble complex)
Presence of chloride is confirmed CHEMISTRY
4Cl- + K2Cr2O7 + 6H2SO4→ 4HSO4- +2KHSO4 + 2 CrO2Cl2↑(orange brown gas chromyl chloride) + 3H2O
CrO2Cl2 + 4NaOH → Na2CrO4 (yellow solution)+ 2H2O + 2NaCl
Na2CrO4 + (CH3COO)2Pb → PbCrO4(yellow ppt) + 2 CH3COONa.
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D WET TESTS (GROUP ANALYSIS) -
Preparation of original solution or water extract if the salt is soluble in water:-
A two nickel of the salt is shaken well with 7ml of water and is called water extract. This is called original solution used for group analysis and confirmatory test for cations.
Sl. No. | EXPERIEMENT | OBSERVATION | INFERENCE |
1. | A little of the solid salt is heated with NaOH solution | Pungent Ammonia smelling gas gives white fumes when glass rod dipped in conc.HCl is shown | GROUP 0 CATION AMMONIUM PRESENT CHEMISTRY On heating with NaOH ammonia gas is evolved NH4+ + NaOH → Na+ + H2O + NH3(g)↑ HCl + NH3(g) → NH4Cl (white fumes) + H2O |
2. | To a little of the original solution added dil.HCl | No characteristic reaction | Absence of group I cations |
3. | To a little of the original solution added dil. HCl and passed H2S gas | No characteristic reaction | absence of group II cations |
4. | To a little of the original solution added ammonium chloride and added ammonium hydroxide till the solution smells of ammonia | No characteristic reaction | Absence of group III cation |
5. | To the mixture of ammonium chloride, ammonium hydroxide mixture solution H2S gas is passed | No characteristic reaction | Absence of group IV cations |
6. | To the mixture of ammonium chloride, ammonium hydroxide mixture added ammonium carbonate solution | No characteristic reaction | Absence of group V cations |
7. | To a little of the original solution added ammonium chloride, ammonium hydroxide then added ammonium hydrogen phosphate | No characteristic reaction | Absence of group VI cations |
E CONFIRMATORY TESTS FOR CATIONS IDENTIFIED UNDER GROUP ANALYSIS
GROUP ZERO CONFIRMATORY TEST FOR AMMONIUM CATION NH4+
1.
| Nesslers reagent test:-A little of the salt added with NaOH solution warmed and to the mouth of the test tube, filter paper dipped in Nessler s reagent is shown. | Filter paper turned brown in colour | Presence of ammonium ion confirmed CHEMISTRY 2[K2HgI4] + NH3(g)↑+ 3KOH → NH2.HgO.HgI↓(brown ppt) +7KI + 2 H2O |
RESULT
The given salt contains Cation = Ammonium (NH4+)
Anion= Chloride (Cl-1) Salt = Ammonium Chloride NH4+Cl
