1.
PRACTICALS
CLASS : XII
V. MEENAKSHI M.Sc., M.Ed.,
GKSVV AMBATTUR

2.
MARKS: 30 TIME : 3 HOURS
Volumetric Analysis -8 marks
Salt Analysis - 8 marks
Content Based Experiment- 6 marks
Project & Viva - 4 marks
Record & Viva - 4 marks
Total -30 Marks

3.
Type of solution
Standard solution
Primary standard solution
Secondary solution

4.
MENISCUS
Lower- colourless
Upper- Coloured

5.
TYPE OF TITRATION
Acidimetry &
Alkalimetry
Permanganometry
Iodometry

6.
Permanganometry
Oxidising agent – KMnO4
Reducing agent- FAS, Oxalic acid
MnO4 -  Mn2+ ( +7 to +2 in acidic medium)
In Basic medium ?
Fe2+  Fe3+ (Oxidised)
(C2O4) 2-  CO2 (Oxidised)

7.
*What is standard solution?
Ans: A solution whose strength is known is called a standard
solution.
* What is normal solution?
Ans: A solution containing one gram-equivalent mass of the solute
per litre of the solution is called a normal solution.
*What is the equivalent mass of KMnO4when it act as oxidizing
agent in acidic medium?
Ans: KMnO4loses 5 electrons per molecule, when it acts as
oxidizing agent in the presence of acids. Therefore,its equivalent
mass is one-fifth of its molecular mass.
Eq. mass= Mol.mass = 158 =31.6
5 5

8.
* What is the principle of volumetric analysis?
Ans: In volumetric analysis, the concentration of a
solution is determined by allowing a known volume
of the solution to react,quantitatively with another
solution of known concentration.
*What is indicator?
Ans: Indicator is a chemical substance which
changes colour at the end point.
* What is end point?
Ans: The stage during titration at which the reaction
is just complete is known as the end point of titration.

9.
*Why does KMnO4 act itself as an indicator?
Ans : In the presence of dilute sulphuric acid,KMnO4 reacts with reducing
agent (oxalic acid or ferrous sulphate). When all the reducing agent has
been oxidized, the excessof KMnO4 is not decomposed and imparts pink
colour to the solution.
* What is the end point in KMno4 titration?
Ans: From colourless to permanent light pink.
*Why is Mohr’s salt preferred as a primary standard over ferrous sulphate
in volumetric analysis?
Ans: This is because of the fact that Mohr’s salt is stable and is not readily
oxidized by air. Ferrous sulphate gets oxidized to ferric sulphate.
* Why are a few drops of dilute sulphuric acid added while preparing a
standard solution of Mohr’s salt?
Ans: Few drops of H2 SO4 are added to prevent the hydrolysis of ferrous
sulphate.

10.
Sometimes a brown ppt.is observed in KMno4 titrations.
Why?
Ans: It is due to insufficient quantity of dil. Sulphuric acid.
Brown coloured ppt. (MnO2.H2O) is formed due to the
incomplete oxidation of KMnO4.
2KMnO4 + H2O → 2KOH + 2MnO2 + 3 [O]
Why should you heat the oxalic acid solution to a about 60-
700C before titrating with KMnO4 solution?
Ans: In cold ,the reaction is very slow due to the slow
formation Mn2+ ions.Oxalic acid is heated to speed up the
liberation of Mn2+ ionswhichthenautocatalyses the reaction
and thus the reaction proceeds rapidly. This also serves the
purpose of expelling the carbondioxide evolved during the
reaction which otherwise does not allow the reaction to go to
completion

11.
QUALITATIVE
ANALYSIS
OR
SALT ANALYSIS

12.
*What is the chemistry of flame test?.
Ans: In flame test, the valence electron of an
atom gets excited and jumps to the higher
level. When the electron jumps back to the
ground state the radiation is emitted those
frequency falls in the visible region
* Why do we use conc.HCl in preparing paste of
the salt for flame test?
Ans:In order to convert metal salts into
metal chlorides which are more volatile
than other salts.

13.
*Co2 and SO2 both turn lime
water milky. How will you
distinguish between them?
Ans: By passing through
acidified K2Cr2O7 solution.
SO2 turns K2Cr2O7 green
while CO2 has no effect.

14.
CATION ION ANALYSIS
Based on common ion effect
&
solubility product
CONDITION FOR PRECIPITATION
KIP > KSP

15.
HCl H+ + Cl-
.
Hydrocholoric acid being a strong acid is largely ionized to H+.
Thus hydrogen ion concentration is increased and consequently
the concentration of sulphide ions produced by the ionization of
H2S is sufficiently decreased due to common ion effect. As a
result of which the sulphide ion concentration is sufficient only to
exceed the solubility product of the sulphides of group II
cations.Since the solubility products (Ksp) for the sulphides of
groups III and IV cations are very high, those cations are not
precipitated out under the above conditions
Why is it essential to add dil.HCI before proceeding
to the test for the basic radicals of group II?
Ans: In the precipitation of group II cations as their
sulphides. H2S is used in the presence of dil. HCI.
H2S is itself a weak acid and dissociates as follows.
H2S 2H+ + S2-

16.
*Why is NH4CI added along with
NH4OH in III group?
Ans: It is done in order to decrease the
concentration of OH- ions by suppressing the
ionization of NH4OH by common ion effect. If
NH4 OH alone is used in that case, the
concentration of OH- is enough to ppt. the
hydroxide of IV, V and VI groups.
* What is blue lake?
A: It is blue particles (blue litmus absorbed on
white ppt.ofAl(OH)3 floating in colourless
solution.

17.
* H2S gas is passed in presence of NH4OH in group
IV. Explain why?
A:When H2S gas is passed in alkaline medium or
NH4OH, the H+ ions from the dissociation of H2S gas
combine with hydroxyl ions (OH-) from the
dissociation of NH4OH to form nearly unionized H2O.
H2S 2H+ + S2-
2NH4OH  2OH- + 2NH4
+
H+ + OH- H2O
The removal of H+ ions from the solution causes
more of H2S to dissociate , thereby increasing the
concentration of S2- ions to such an extent that the
ionic product of IV group metal sulphides exceeds
their solubility product. Hence they are precipitated.

18.
Presence of NH4Cl is quite essential before the
additions of (NH4)2CO3 in group V. Explain
why?
Ans: Ammonium chloride suppresses the
ionization of NH4OH and (NH4)2CO3 due
to common ion effect which results in the
decrease in the concentration of OH- and
CO3
2- ions. So the ionic product does not
exceed the solubility product of Mg(OH)2
or MgCO3 and thereby they are not
precipitated in V group.

19.
CONTENT BASED EXPERIMENT
SOL PREPARATION
CHROMATOGRAPHY
FUNCTIONAL GROUPANALYSIS
KINETICS
DOUBLE SALT
FOOD TEST

20.
COMMON REAGENTS
REAGENTNAME
&
CHEMICAL NAME

21.
•Read all the experiments carefully and
thoroughly From your record.
•Follow the sequence given by your
teachers to write the paper.
•Present your paper neatly, draw tables,
lines wherever required. This will create a
good impression and the external will be
happy to check that paper.
•For your viva, be confident.
Tips for PRACTICAL EXAM

22.
ALL THE BEST