ANALYSIS OF SALT 3 ( Ammonium carbonate )
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.
A) PRELIMINARY TESTS |
1. a) | Colour of the salt noted | White coloured
| absence of Cu 2+ , Fe 2+, Fe 3+, Ni 2+, Co2+, Mn2+ ions
|
b) | Smell noted : - with a drop of water rub the salt | ammoniacal smell
| ammonium ions present |
2. | DRY HEATING TEST A small amount of the salt is heated in a dry test tube. | i) colourless, odourless gas turning lime water milky
iii) ammoniacal smell
| i) Presence of carbonate salt CHEMISTRY MCO3→MO + CO2↑ Ca(OH)2 + CO2→ CaCO3 (white or milkiness)
iii) ammonium NH4+salt may be present CHEMISTRY :- On heating the ammonium salt liberates ammonia gas |
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 |
a | COBALT NITRATE TEST/ASH TEST To a little of the salt solution a few drops of conc. HNO3 and cobalt nitrate solution dip a filter paper into the solution and burnt into ashes(warm if needed) | 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 ml of dil. H2SO4 | i) Brisk effervescence with colourless, odourless gas turning lime water milky | i) Presence of carbonate salt CHEMISTRY CO3 2-+ H2SO4→ SO4 2- + CO2↑ + H2O Ca(OH)2 + CO2→ CaCO3 (white or milkiness)
|
2. | CONC. SULPHURIC ACID TEST - a little of the salt is added with drops of conc. H2SO4 | no characteristic reaction | absence of chloride, nitrate and acetate
|
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 |
CONFIRMATORY TEST FOR CARBONATE |
1. Dil. HCl test :- A little of the water extract of the salt is treated with Dil HCl
2. BaCl2 test:- A little of the water extract of the salt is treated with few drops of BaCl2 solution and dil .HCl is added to it | Brisk effervescence with the evolution of colourless, odourless gas turning lime water milky
White precipitate soluble in dil. HCl
| Presence of carbonate confirmed CHEMISTRY CO3 + 2HCl → 2Cl- + CO2↑ + H2O
Ca(OH)2 + CO2→ CaCO3 (white or milkiness)
Presence of carbonate confirmed CHEMISTRY CO32- + BaCl2 → BaCO3 (white ppt)+ 2Cl-
BaCO3 (white ppt) + 2HCl → . BaCl2 + CO2↑ + H2O |
D (GROUP ANALYSIS) - Preparation of original solution – A little of the salt is mixed well with water to get original solution in a test tube
Sl. No. | EXPERIEMENT | OBSERVATION | INFERENCE |
1. | salt + NaOH + heat | Pungent Ammonia smelling gas gives white fumes when glass rod dipped in conc.HCl is shown | Presence of group 0 cation ammonium NH4+ On heating with NaOH ammonia gas is evolved NH4+ + NaOH → Na+ + H2O + NH3(g)↑ HCl + NH3(g) → NH4Cl (white fumes) + H2O |
2. | OS + dil.HCl | No characteristic reaction | Absence of group I cations Pb2+ |
3. | OS + dil. HCl + H2S gas | No characteristic reaction | absence of group II cations Cu2+ |
4. | OS+NH4Cl + NH4OH | No characteristic reaction | Absence of group III cation Al 3+ , Fe 3+ |
5. | OS+NH4Cl + NH4OH +H2S | No characteristic reaction | Absence of group IV cations Zn2+ ,Ni,2+ Co2+ and Mn2+ |
6. | OS+NH4Cl+ NH4OH +(NH4)2CO3 |
No characteristic reaction
| Absence of group V cations Sr2+, Ba2+ , Ca2+
|
7. | OS+NH4Cl + NH4OH + ammonium hydrogen phosphate solution | No characteristic reaction | Absence of group VI cations Mg2+ |
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= Carbonate (CO32-)
Salt = Ammonium Carbonate (NH4)2CO3
