useful for class 12 students

1. MOST IMPORTANT
V IVA Questions
CHEMISTRY
BOURDs
PRACTICALS
· Bharat Panchal Sir
Bharat Panchal-Chemistry Gurujic
.

2. qualitative chemical analysis, branch of chemistry that deals with
the identification of elements or grouping of elements present in a
sample.
Negatively charged radicals are called acidic radicals. Positively charged
radicals are called a basic radical.

3. Due to the high dielectric constant of water, the force of attraction
holding the two ions in a salt decreases. Thus, the two ions
separate
Cu2+,Fe2+, Fe3+, Cr3+, Ni2+, Co2+ and Mn2+
Cu2+,Fe2+, Fe3+, Cr3+, Ni2+, Co2+ and Mn2+

4. Due to the formation of black lead-sulphide by the action of
H2S in atmosphere
96 . Name the colour iron and wickel salts
.
An felt -
light Green
Nict-Bluish Green
fest -
Brown
97.
Why a salt
containing lead turns black in
colour when placed for a
long time in lab?
(CH> (00P6tHS -
> PbSt
lead sulphide
+ P
· Bharat Panchal Sir
(Black in Colour)
Bharat Panchal-Chemistry Gurujic
.

5. Mg has very high ionisation energy it has one more proton in its nucleus
to hold on to the electrons in the 3s orbital, so it does not impart any
characteristic color to the Bunsen burner flame.
A flame test is an analytic procedure used in chemistry to
detect the presence of certain elements, primarily metal
ions, based on each element's characteristic emission spectrum.

6. 910:
why do we use couc. He in preparing
a paste of the salt
for flame test!
A
· Bharat Panchal Sir
Bharat Panchal-Chemistry Gurujic
.

7. This is because glass contains sodium silicate which imparts its
own golden yellow colour to the flame.
1) Platinum doesn't impart any color to the flame.
2) It is not oxidised under the high temperature of the flame from a bunsen burner.
3) It is almost chemically inert. Even at high temperatures, it remains unattacked
by free radicals / acid radicals.

8. Because their ionisation energies are high, so they need large amount of
energy for the excitation of their valence electrons to higher energy level
which is usually not available in the bunsen flame. So they do not impart
any colour to the flame.

10. When the salt is treated with HCl, during reaction HCl gas is also
given out along with the gas evolved by the salt. So the actual gas
cannot be identified whereas with H2SO4, no such problem arises
The white ppt. of CaCO3 changes into soluble calcium bicarbonate and the
milkiness, therefore, disappears.

13. The chromyl chloride test is used to detect chloride ions in the
qualitative analysis. If any chloride salt like sodium chloride is
heated with acidified potassium dichromate it produces red
colour fumes of chromyl chloride. It confirms the presence of
chloride ions in that salt.
922.
what is chromyl chloride Test ?
Am
-
Naut Conc Hason + K
,201 -
> Cro
, Or
Chromy Chloside
Creddish Brown)
Croc +
Ho-HCrOy Yellow
HacrOut Naon +
(Chy200lPb -
> PbCrOu
Yellow Opt
Clead (normate (

14. Nitric acid is generally not used for preparation of original
solution in analysis of basic radicals, because it is an oxidizing
agent which will convert all low oxidation cations into higher
one and these cations can not be recognised in presence of this
acid.

16. Question. What is the principle of volumetric analysis?
Answer. 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.
Question. Burette and pipette must be rinsed with the solution with which they
are filled, why ?
Answer. The burette and pipette are rinsed with the solution with which they
are filled in order to remove any water sticking to their sides, which otherwise
would decrease the cone, of the solutions to be taken in them.
Question. Why a titration flask should not be rinsed ?
Answer. This is because during rinsing-some liquid will remain sticking to the
titration flask therefore the pipetted volume taken in the titration flask will
increase.

17. Question. What is a molar solution ?
Answer. A molar solution is a solution, a litre of which contains one gm-mole
of the substance. This is symbolised as 1M.
Question. What is titration ?
Answer. The process of adding one solution from the burette to another in the
conical flask in order to complete the chemical reaction involved, is known as
titration.
Pipette should never be held from its bulb, why ?
Answer. The body temperature may expand the glass and introduce an error in
the measurement volume.

18. 1. What is qualitative analysis ?
Ans. The type of analysis that deals with the methods which
are used to determine the constituents of a compound.
2. What is a radical ?
Ans. A radical may be defined as an atom or group of atoms
which carries charge and behaves as a single unit in
chemical reactions.
3. What are acidic and basic radicals ?
Ans. Radicals carrying positive charge are called basic
radicals and those carrying negative charge are called
acidic radicals.
4. What type of bond is present in an inorganic salt ?
Ans. Electrovalent bond.
5. Why do inorganic salts ionise when dissolved in water ?
Ans. Due to the high dielectric constant of water, the force of
attraction holding the two ions in a salt decreases. Thus, the
two ions separate. The ions are further stabilized by
solvation.
6. Give examples of some coloured basic radicals.
Ans.Cu2+,Fe2+, Fe3+, Cr3+, Ni2+, Co2+ and Mn2+.
7. What is the colour of iron salts ?
Ans. Ferrous salts are usually light green while ferric salts
are generally brown.
8. Name any iron salt which is light green.
Ans. Ferrous sulphate.
9. What is the colour of nickel salts ?
Ans. Bluish green or green.
10. What is the colour of manganese salts ?
Ans. Light pink or flesh colour.

19. 11. Name the basic radicals which are absent, if the given salt is
white.
Ans. Cu2+,Fe2+, Fe3+, Cr3+, Ni2+, Co2+ and Mn2+.
12.Why a salt containing lead turn black in colour, when placed
for a long time in labora-tory?
Ans. Due to the formation of black lead sulphide by the action of
H2S in atmosphere.
13. Name the salts which produce crackling sound when heated.
Ans. Lead nitrate, barium nitrate, potassium bromide, sodium
chloride.
14. What is sublimation ?
Ans. It is the process by which a salt directly changes into gaseous
phase without melting, when heated. On cooling vapours condense
back to the solid state.
15. Tell the importance of preliminary tests in qualitative
analysis.
Ans. Sometimes, preliminary tests give authentic information
about an ion in the salt. For example, golden yellow colour in flame
test shows the presence of sodium. In a charcoal cavity test,
brown residue shows the presence of cadmium in a salt and so on.
16. How is dry heating test performed and what information you
get if the residue changes to yellow when hot ?
Ans. In dry heating test, the salt is heated in a dry test tube.
Yellow residue when hot shows the presence of Zn2+ ion.
17. What is the expected observation when copper sulphate is
heated in a dry test tube ? Ans. A white residue is formed and
water condenses on the colder walls of the test tube.
18. Name the radical which produces CO2 on heating.
Ans. Carbonate.
19. What is the colour of residue when zinc salt is heated ?
Ans. A residue yellow when hot and white when cold is formed.
20. What is the colour of residue when cadmium salt is heated ?
Ans. A residue brown when hot, brown when cold.

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