ANALYSIS OF SALT 6 ( Barium nitrate)
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 | no characteristic smell | Absence of ammonium and acetate ions |
2. | DRY HEATING TEST A small amount of the salt is heated in a dry test tube. | The salt decrepitates (cracking)
| Nitrate salt may be present
|
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. | grassy apple green
| Ba2+ ions may be present CHEMISTRY Certain salts on reacting with conc.HCl form their chlorides that are volatile in nonluminous flame. Due to heat of the flame the electrons are excited to higher energy levels and on coming back they impart characteristic colour to the flame. |
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 | no characteristic reaction | absence of carbonate |
2. | CONC. SULPHURIC ACID TEST - a little of the salt is added with drops of conc. H2SO4 | reddish brown gas with pungent smell is evolved when heated with Cu turnings
| Presence of nitrate CHEMISTRY:- Cu acts as reducing agent and reduces nitric acid to NO2 gas. NO3- + H2SO4→ HSO4- + HNO3 4 HNO3 + Cu → Cu(NO3)2 + 2 NO2↑ + 2H2O |
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 NITRATE |
1. Paper ball test:- Add a small quantity of the salt with conc. H2SO4 and a paper ball and warm if needed
2. Brown ring test:- a) take a test tube add a small quantity of ferrous sulphate crystals and dissolve it in water. This is freshly prepared ferrous sulphate solution. b) To a little of the water extract of the salt add a small quantity of freshly prepared FeSO4 and then pour conc. H2SO4 slowly along the sides of the test tube | Dark brown fumes of nitrogen di oxide are evolved
A dark brown ring is formed at the junction of the layers of the acid and the solution | Presence of nitrate is confirmed Paper ball C acts as reducing agent and reduces nitric acid to NO2 gas. CHEMISTRY NO3- + H2SO4→ HSO4- + HNO3 4 HNO3 + C → CO2 + 4 NO2↑(reddish brown gas) + 2H2O
Presence of nitrate confirmed CHEMISTRY:- NO3- + H2SO4→ HSO4- + HNO3
6 FeSO4 + 3 H2SO4 + 2 HNO3→3Fe2(SO4)3 +4 H2O +2NO
FeSO4 + NO + 5H2O →[Fe(NO)(H2O)5] SO4brown ring
|
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 | No characteristic reaction | Absence of group 0 cation ammonium NH4+ |
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 | White precipitate
| PRESENCE OF GROUP V CATION Ba2+ CHEMISTRY Ba2+ + (NH4)2CO3 → BaCO3 + 2NH4+ |
7. | OS+NH4Cl + NH4OH + ammonium hydrogen phosphate solution | No characteristic reaction | Absence of group VI cations Mg2+ |
E CONFIRMATORY TEST FOR Ba2+ White Barium carbonate dissolves in hot dilute acetic acid
BaCO3 + 2 CH3COOH → H2O + CO2↑ + (CH3COO)2Ba
1.
2. | 1. Potassium chromate test:- To one part of the solution, add a few drops of potassium chromate solution 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. | Yellow precipitate
grassy apple green
| barium confirmed CHEMISTRY - (CH3COO)2Ba + K2CrO4 → BaCrO4(yellow ppt) + 2 CH3COOK Presence of barium cation confirmed. Chemistry written in preliminary tests itself |
RESULT The given salt contains Cation = Barium (Ba2+) Anion = Nitrate (NO3-)
Salt = Barium nitrate Ba(NO3 )2
