Experiment QA1
Qualitative Analysis
Name:
Seat No.:
Date:
Grade:
1. Describe the sample.
2. Report on the solubility of the sample in
water.
3. Estimate, using universal test paper, the pH
of an aqueous solution of the sample.
4. Heat a small amount of the solid sample in
an ignition tube, at first gently and then
strongly.
Report the observations.
5. Carry out a flame test and report the
observations.
6. Report on the action of 2 M H2SO4 on an
aqueous solution of the sample.
7. Report on the action of conc. H2SO4 on the
solid sample.
8. Report on the action of conc. HNO3 on the
solid sample.
9. Report on the action of 2 M NaOH on an
aqueous solution of the sample.
10.Report on the action of dilute aqueous
NH3 on an aqueous solution of the sample.
11.Report on the action of a few drops of 0.2
M KMnO4 in 2 M H2SO4 on an aqueous
solution of the sample.
12.Report on the action of zinc and 2 M
H2SO4 on an aqueous solution of the
sample.
From the result of the above tests, deduce which cation(s) and anion(s) may be present in the
solid sample.
P.1
Experiment QA1 Qualitative Analysis
1.
Describe the sample.
Solid, liquid, gas.
e.g. i.
Green solid.
ii.
Brown solution.
iii.
White crystalline solid.
iv.
Colourless liquid.
v.
Blue liquid.
vi. Yellow viscous liquid.
Colour
Inference
Red
HgO, Ag2CrO4, Cu2O
Orange
Cr2O72-
Yellow
AgI, AgBr, Fe3+(dil.)
Green
CuCO3, Fe2+, Cr3+
Blue
Cu2+
Purple
MnO4-
Brown
Fe3+(conc.)
Black
CuO, MnO2, CuS, PbS
Pink
Co2+
White
Most compounds.
Probably does not contain a transition metal
2.
Report on the solubility of the sample in water.
e.g. i.
ii.
Very soluble.
Soluble.
iii. Slightly soluble.
iv.
Insoluble.
1.
All salts of group I cations and NH4+ are soluble.
2.
All nitrates are soluble.
3.
All ethanoates are soluble.
4.
All sulphates are soluble except those of Ba2+, Ca2+, Sr2+ and Pb2+.
5.
All chlorides/bromides/iodides are soluble except those of Ag+, Cu+, Pb2+ and Hg22+.
6.
All carbonates/phosphates/sulphites are insoluble except those of group I cations and
NH4+.
7.
All hydroxides are insoluble except those of group I cations, NH4+, Sr2+ and Ba2+.
8.
All sulphides are insoluble except those of group I and group II cations and NH4+.
P.2
Experiment QA1 Qualitative Analysis
3.
Estimate, using universal test paper, the pH of an aqueous solution of the sample
e.g. i.
pH = 2
ii.
pH = 7
iii. pH = 13
iv. pH = 9.5
4.
Heat a small amount of the sample in an ignition tube, at first gently and then
strongly.
Report the observations.
e.g. i.
ii.
Gas evolved.
Pungent gas evolved.
iii. Brown gas evolved.
iv.
Sublimation.
v.
Decrepitation. (spitting and cracking)
vi. Charring. (carbon produced)
vii. Colourless liquid condenses on cooler parts of tube.
Observation
Inference
Sublimation.
NH4+ salts.
Decrepitation,
Anhydrous salts that decompose with evolution of gas.
spitting and cracking.
e.g. Pb(NO3)2, KMnO4.
Charring.
CH3COO-, C2O42-.
(carbon produced)
Gas evolved which
O2 produced by decomposition of oxide or nitrate.
relights a glowing splint.
Gas evolved which turns
CO2 produced by decomposition of carbonate or
lime water milky.
hydrogencarbonate.
Gas evolved which burns
CO from decomposition of oxalate.
with a blue flame.
Brown gas evolved.
NO2 from a nitrate or Br2 from a bromide.
Colourless liquid
Probably water from the decomposition of a hydrate,
condenses on cooler parts
a hydroxide or a hydrogencarbonate.
of tube.
Pungent gas evolved
NH3 from decomposition of ammonium salt.
which is alkaline.
P.3
Experiment QA1 Qualitative Analysis
5.
Carry out a flame test and report the observation.
Flame colour
Inference
Persistent yellow
Na+
Lilac
K+
Ca2+, Sr2+, Li+
Red/Orange
6.
Pale green
Ba2+
Greenish blue
Cu2+
Report on the action of 2M HCl/2M H2SO4 on an aqueous solution of the sample.
Observation
Inference
Gas evolved which turns lime water milky.
Gas evolved has a pungent smell, is acidic
and turns dilute KMnO4 colourless.
CO2 from CO32- or from HCO3SO2 from SO32-
Gas evolved smells with bad eggs and
gives a black precipitate with lead nitrate
H2S from S2-
solution.
Pungent acidic gas is evolved and a pale
yellow precipitate forms.
SO2 or S from S2O32NO2 from NO2-
Dark brown acidic gas evolved.
Pale green gas evolved which bleaches
Cl2 from ClO-
indicator.
Acidic gas evolved which smells of
CH3COOH from CH3COO- or
vinegar.
HCOOH from HCOO-
P.4
Experiment QA1 Qualitative Analysis
7.
Report on the action of conc. H2SO4 on the solid sample.
e.g. i.
Colourless gas evolved.
ii. Brown fumes evolved.
Observation
Inference
Pale yellow vapour.
Possibly HNO3 vapour from NO3-
Steamy fumes evolved which give dense
HCl from Cl-
white smoke with NH3(g).
Brown-orange fumes.
Br2 from Br-
Purple fumes.
I2 from I-
Gases evolved which burn with a blue
CO and CO2 from C2O42-
flame and turn lime water milky.
Gas evolved which burns with a blue
CO from HCOO-
flame.
8.
Report on the action of conc. HNO3 on the solid sample.
e.g. i.
Brown fumes evolved.
(most reducing agents such as C, S, SO32-)
ii. Black precipitate. (Inference: I-)
(I- + NO3- + 2H+  I2 + NO2 + H2O)
9.
Report on the action of 2 M NaOH on an aqueous solution of the sample.
e.g.
i.
A blue gelatinous precipitate forms.
ii. A white gelatinous precipitate soluble in excess NaOH.
iii No precipitate at any stage.
Observation
Inference
Mg2+, Al3+, Zn2+
White gelatinous precipitate.
Dirty green gelatinous precipitate.
Fe2+
Reddish brown gelatinous precipitate.
Fe3+
Pale blue gelatinous precipitate.
Cu2+
Dark brown precipitate.
Ag+
White powder gelatinous precipitate
Pb2+
Na+, K+, NH4+
No precipitate.
Note:
Al(OH)3, Zn(OH)2 and Pb(OH)2 are soluble in excess 2M NaOH.
P.5
Experiment QA1 Qualitative Analysis
10. Report on the action of dilute aqueous NH3 on an aqueous solution of the sample.
e.g.
i.
White precipitate formed.
ii.
Initial pale blue precipitate which dissolves to form deep blue solution.
Observation
White gelatinous
Inference
Action of excess NH3 on precipitate
Mg2+/Al3+
Insoluble
precipitate
White gelatinous
Zn2+
precipitate
ppt dissolves to form colourless
solution
Pb2+
Insoluble
Dirty green precipitate
Fe2+
Insoluble
Reddish brown
Fe3+
Insoluble
Cu2+
ppt dissolves to form deep blue
White powderly
precipitate
precipitate
Pale blue precipitate
solution
Dark brown precipitate
Ag+
ppt dissolve to form colourless
solution
11. Report on the action of a few drops of 0.2 M KMnO4 on an aqueous solution of the
sample.
e.g. i
ii.
No visible change.
The acidified KMnO4 solution is turned from purple to colourless. (This indicates
that the sample is a reducing agent)
12. Report on the action of zinc and 2M H2SO4 on an aqueous solution of the sample.
e.g. i.
ii.
No visible change.
The aqueous solution of the sample decolourized.
iii. Colour of solution changes from orange to green.
N.B. Any positive result shows that the sample is an oxidizing agent.
P.6
Experiment QA1
Gas
Colour
Qualitative Analysis
smell
Test
Burns with a ‘pop’
Hydrogen
Colourless
Odourless
Equations
2H2+O2  2H2O
sound
Oxygen
Colourless
Odourless
Relights glowing splint
Carbon
dioxide
Colourless
Odourless
Turns lime water milky
CO2+Ca(OH)2  CaCO3 +H2O
Colourless
Odourless
Burns with blue flame
2CO+O2  2CO2
Carbon
monoxide
a. turns red litmus blue
Pungent
Ammonia
Colourless
b. forms white fumes
NH3+HCl  NH4Cl
smell
with HCl
Hydrogen
Irritating
forms white fumes with
smell
NH3
Choking
Turns blue litmus red
yellow
smell
and then bleaches it
Reddish
Choking
Turns blue litmus red
smell
and then bleaches it
Colourless
chloride
Greenish
Chlorine
Bromine
brown
NH3+HCl  NH4Cl
Cl2+H2O  HCl+HOCl
Br2+H2O  HBr+HOBr
Choking
Iodine
violet
Turns starch blue
smell
Turns acidified
Sulphur
Cr2O72-+14H++6e-  2Cr3+
Sulphur
Colourless
dioxide
potassium dichromate
smell
green
Nitrogen
+7H2O
SO2+2H2O  4H++SO42-+2e-
Pungent
brown
dioxide
Turns blue litmus red
smell
Nitrogen
Forms brown fumes in
Colourless
Odourless
monoxide
2NO+O2  2NO2
air
Turns anhydrous
Water
Colourless
Odourless
copper(II) sulphate
vapour
blue
P.7
CuSO4+5H2O  CuSO45H2O