Qualitative Analysis
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Transcript of Qualitative Analysis
1/4/2016 Embibe
http://www.embibe.com/engineering/practice/solve/jee/chemistry/inorganicchemistry/qualitativeanalysis/session 3/9
Observation with dilute H2SO4
Observation Acid Radical Confirmatory Test
Briskeffervescencewith
Gas truns lime water milky but milkyness disappears on passing gas increases.
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Question
. What is the coefficient for OH when this equation is balanced with the smallestinteger coefficients ?
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Explanation
Key Concept
Wet tests for acid radicals : Salt or mixture is treated with dil. H2SO4 and also with conc. H2SO4 separately andby observing the types of gases evolved. Confirmatory tests of anions are performed.
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+ → +Cl2 OH− Cl− ClO−3
3 + 6 → 5 + + 3 OCl2 OH− Cl− ClO−3 H2
+ → + O +Na2CO3 H2 SO4 Na2SO4 H2 CO2
Ca(OH) CO CaCO OH
1/4/2016 Embibe
http://www.embibe.com/engineering/practice/solve/jee/chemistry/inorganicchemistry/qualitativeanalysis/session 4/9
evolution ofcolourlessandodourlessgas.
Brown fumes
Add KI and starch solution blue colour.
Smell ofrotten gas(H2S smell)on heating
Gas turns lead acetate paper black.
Sodium carbonate extract (SE)* + Sodium nitroprusside Purple colour
Colourlessgas withpungentsmell ofburningsulphur
Gas turns acidified K2Cr2O7 solution green [Different from ] since gas also tunrslime water milky
Solutiongives smellof vinegar
White oryellowishwhiteturbidity onwarming.
Observation with concentrated H2SO4
(Carbonate)CO2−3
Ca(OH)2
Lime water
+ CO2 → CaCO3
Milky
+ OH2
CaCO3 + OH2 + CO2 −→− Ca( )HCO3 2
Soluble
(Nitrite)NO−2
2 +NaNO3 H2 SO4
HNO2
−→−−→−
+ 2Na2SO4 HNO2
NO (Colourless)
2 +NaNO3 H2 SO4
HNO2
2NO + (Air)O2
−→−−→−
−→−
+ 2Na2SO4 HNO2
NO (Colourless)
2 (Brown)NO2
2KI + + 2H2 SO4 NHO2
+ StarchI2
−→−
−→−+ 2 O + 2NO +K2SO4 H2 I2
Blue colour
(Sulphide)S2−
S + ⟶ S +Na2 H2 SO4 H2 Na2SO4
SH2 + Pb( COO)CH3 2 −→− PbS
(Black)
+ 2 COOHCH3
SNa2 + [Fe NO]Na2 (CN)5
Sodium
nitroprusside
−→− [Fe NOS]Na4 (CN)5
(Purple)
(Sulphite)SO2−3
CO2−3
+ + O +Na2SO3 H2 SO4 −→−Δ
Na2SO4 H2 SO2
Cr2O2−7 + 3SO2 + 2H+ −→− 2Cr3+
(Green)
+ 3SO2−4 + OH2
(Acetate)CH3COO−
Aq. solution + ⟶ Blood red colourNeutral FeCl3
3 COONaCH3 + FeCl3Neutral
−→− Fe( COO)CH3 3
Red
+ 3NaCl
(Thiosulphate)S2O2−3
Aq. solution + ⟶ White ppt. changing to black on warmingAgNO3
Na2S2O3 + 2AgNO3 −→− Ag2S2O3
White ppt.
+ 2NaNO3
Ag2S2O3 + OH2 −→− S +Ag2 H2 SO4
Black ppt
1/4/2016 Embibe
http://www.embibe.com/engineering/practice/solve/jee/chemistry/inorganicchemistry/qualitativeanalysis/session 5/9
Observation Acid radical Confiramatory Test
Colourless pungent gas involving whilefumes with Aq. NH4OH
Add MnO2 in the same test tube and heatpalegreen Cl2 gas (i)
S.E + HNO3 + AgNO3 solution White ppt.soluble in Aq. NH3 (ii)
Chrmoyl chloride Test (iii)
Raddish brown fumes
Add Mn2O and Heat Yellowish brown Br2gas (iv)
S.E + HNO3 + AgNO3 solution Pale yellowppt. partially soluble in aq. NH3 (v)
Layer test (vi)
Violet pungent vapours turning starch paperblue.
S.E + HNO3 + AgNO3 Yellow ppt.insoluble in aq. NH3 (vii)
Layer test (vi)Brown pungent fumes intensified by theaddition of Cu turnings. Ring test (viii)
Colourless gas turning lime water milky andburning with blue flame.
Acidified KMnO4 solution is decolorised (ix)
S. E + CH3COOH + CaCl2 white ppt.decolorising acidified KMnO4 solution (x).
ALUMINIUM
1.Add Nessler's Reagent to salt solution.
RESULT: Purple precipitate appears.
2.Add Sodium Hydroxide solution to salt solution.
RESULT: White precipitate appears. It dissolves in excess Sodium Hydroxide solution.
3.Add 2 ml of Sodium Hydroxide solution to salt solution and add Aluminon reagent.
RESULT: Reddish precipitate appears
AMMONIUM
1.Add salt solution with a few drops of Nessler's solution and excess amount of Sodium Hydroxide.
RESULT: Brown precipitate appears.
2.Add salt with Sodium Hydroxide and heat it.
RESULT: Gas with smell of Ammonia comes. It turns Red litmus into Blue and gives white fume with glass bar,soaked in Conc. Hydrochloric acid.
ANTIMONY
Add 5 ml of diluted HCl to salt. Pass H2S.Precipitate appears. Dissolve it by adding diluted HCl. To it add KOH andBromine water. Add solid NH4Cl and boil for a few minutes. Filter it and add diluted HCl. Pass H2S.
RESULT: Orange colour precipitate appears.
ARSENIC
(Chloride)Cl−
(Bromide)Br−
(Iodide)I−
⟶
(Nitrate)NO−3
(Oxalate)C2O2−4
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Add pure Zinc and diluted H2SO4 to an arsenic compound. Cover the mouth of the test tube with filter paper soakedin AgNO3. RESULT: The paper first turns Yellow and then black.
BARIUM
1.Add 5 ml of HCl to Salt. Add NH4OH and NH4Cl.Add strong solution of Ammonium carbonate. Boil and filter.Precipitate appears. Add hot dil Acetic acid and add K2CrO4 solution.
RESULT: Yellow precipitate appears.
Dissolve it in HCl. Add S2S2 solution.
RESULT: White precipitate appears.
BISMUTH
Add 5 ml of diluted HCl to salt. Pass H2S.Precipitate appears. Boil it with 5 ml of diluted Nitric acid. Add 5ml ofConc. H2SO4. Add Thio Urea.
RESULT: Yellow colour precipitate appears.
CADMIUM
Add 5 ml of diluted HCl. Pass H2S.Precipitate appears. Boil it with 5ml of diluted Nitric acid .Add 5 ml ofConc.H2SO4. Add Ammonium Hydroxide.
RESULT: Yellow precipitate appears.
CALCIUM
1.Add salt solution and 2 ml of Potassium Chromate solution.
RESULT: No precipitate.
2.Add salt solution and 1 ml of Ammonium chloride and 1 ml of Ammonium Hydroxide and 2 ml of Ammoniumoxalate.
RESULT: White precipitate appears. It does not dissolves in Acetic acid.
CARBONATE
Add a few ml of diluted HCl to a little substance in a test tube.
RESULT: Brisk effervescence. Colourless,odourless gas turning lime water milky.
CHROMIUM
Add 5 ml of diluted HCl to salt. Add NH4Cl. Precipitate appears. Boil it with Sodium Peroxide. Precipitatedissolves. Add acetic acid and lead acetate.
RESULT: Yellow precipitate appears.
COBALT
1.Add 5ml of dil HCl to salt and boil it. Add 1ml of Amyl alcohol ether and 1 ml of NH4CNS solution. Shake well.
RESULT: The upper layer is colour edintense blue.
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2.Add 5 ml of HCl to salt. Boil it .Add 2 ml of ZnSO4 solution. Soak a roll of filter paper and burn the wet end.
RESULT: The ash will be green.
COPPER
1.Add Ammonium Hydroxide solution .Then light blue precipitate appears. Add excess Ammonium Hydroxide.
RESULT: It will become dark blue.
2.Add 2 ml of Potassium Fluoride to salt solution.
RESULT: Chocolate brown colour precipitate appears.
FERRIC
1.Add 2 ml of Potassium Ferro cyanide to salt solution. RESULT: Blue precipitate appears.
2.Add 2ml of Ammonium Thio cyanide solution to salt solution.
RESULT: Bloddish red appears.
FERRUS
Add Pottassium Ferri cyanide to the salt solution
RESULT: Blue precipitate appears
LEAD
1.Add 2 ml of Potassium Chromate to salt solution.
RESULT: Yellow precipitate appears.
2.Add 2 ml of Potassium Iodide solution.
RESULT: Yellow precipitate appears. This becomes glittering gold particle when hot water is added and cooled.
MANGANESE
Add 5 ml of diluted HCl to salt. Add NH4Cl .Precipitate appears. Add Benz dine and acid.
RESULT: The precipitate turns Blue.
MERCURY
1.Add 5 ml of Hydrochloric acid to little substance. RESULT: Precipitate appears.
Boil the precipitate with water. It does not dissolves. Add Sodium Hydroxide solution. Heat it and filter.
RESULT: Black precipitate appears.
2.Add 5 ml of diluted Hydrochloride acid to salt solution. Pass Hydrogen Sulphide gas. Precipitate appears. Boil itwith 5 ml of diluted Nitric acid and the filter. In one portion add SnCl2 .
RESULT: White precipitate turns grey.
To other portion add KI
RESULT: Red precipitate appears.
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NICKEL
Add HCl to the salt. Boil it. Add NH4Cl,NH4OH and K3Fe(CN)4 to a few drops.
RESULT: Yellowish brown precipitate soluble in NH4OH.
SILVER
1.Add 5ml of HCl. to a little substance. Precipitate appears. Boil the precipitate with water. It does not dissolves.Add Ammonium Hydroxide solution to it.
RESULT: The precipitate dissolves.
Add diluted Nitric acid
RESULT: Curdy White precipitate appears.
STRANTIUM
Add 5 ml of Hydrochloric acid to salt. Add Ammonium Hydroxide and Ammonium Chloride. Add strong solutionof Ammonium Carbonate. Precipitate appears. Dissolve it in hot acetic acid. Add K2CrO4 solution. Filter it. Boilwith Ammonium Sulphate solution.
RESULT: White precipitate appears.
TIN
Add 5 ml of n diluted HCl to salt. Pass H2S. Precipitate appears. Dissolve it by adding diluted HCl. Add KOH andBromine water until the colour of the liquid remains yellow. Add solid NH4OH and boil for a few minutes.Whiteprecipitate appears . Reduce by boiling with iron fillings, Filter and add HgCl.
RESULT: White precipitate appears.
ZINC
1.Add Sodium Hydroxide solution to salt solution.
RESULT: White precipitate appears.
2.Add 2 ml of Potassium Ferro Cyanide solution.
RESULT: White precipitate appears. It dissolves in Sodium Hydroxide solution.
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