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CHEMISTRY
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12th
3Marks
1.Define an Heisenberg’s
uncertainty principle.
It is impossible to measure simultaneously both the position and velocity of a microscopic particle with absolute accuracy (or) certainty.
∆x∆p ≥
∆x -
uncertainty in the position of the particle,
∆p -
uncertainty in the momentum of the particle.
2. Why He2 is
not formed?
Bond order = ½ (Nb – Na) = 2-2/2 = 0
3. Distinguish between
particle and wave
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Particle
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Wave
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1.A
particle is localized in space
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A wave is
delocalized in space
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2.Particle
do not interfere
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wave can
interfere
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3.Total
number of particle in a space is equal to their sum.
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The
resultant wave can be larger or smaller then the individual wave.
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4.Write about hydridisaton.
Intermixing of orbital an atom having
nearly the same energy to given exactly equivalent orbital’s with same energy
identical shape and symmetrical orientation in space
5. Define bond order.
Half the
difference between the number of electron in bond molecular orbitals and the
number of electron in antibond molecular orbitals.
bond order = ½ (Nb – Na)
6. What is the signification of negative electron energy?
ü The energy of an electron
at infinity is arbitarily assumed to zero
ü The influence of nucleus it
does some work and spends its energy in this process
ü The energy of the electron
decreases and it become less than zero.
7. Why electron affinity of fluorine is less than that of chlorine?
Small size of fluorine atom.
These occurs repulsion among electrons of the valency
shell and also with electrons to be added.
8.Why the first ionization
energy of Al is lower then that of Mg?
One has to remove 3p electron in case of aluminium and 3S
electron in the case of magnesium.
9. Disadvantage of pauling
and Mullikan’s scale disadvantage of paulling of paulling scale .
It is that bond energies are not know with any degree of accuracy for
many solid elements.
Disadvantage of mulliken’s
scale:
It is that electron affinities with the exception of a few elements are
not reliably know.
10. Why electron affinity
of Be and N are zero?
Be- 1s2 2s2 fully filled orbital
N- 1s2 2s2 2p3 half
orbital
They have two attain stable electronic configuration and
do not have the tendency to accept electron.
11. Why ionization energy
neon is higher then fluorine?
Neon (Z = 10) has higher nuclear charge than fluorine (Z
= 9).
Neon attains the stable configuration. So the removal or
electron from the outer shell is very difficult
12. Prove that P2O5 is a powerful dehydrating agent.
13. What is inert pair effect?
The electron in the ns
orbital becomes inert and they are less available for bonding .
14. Draw the electron dot formula of PCl5 and H3PO3
15. What is plumbo solvency?
Lead reacts with water containing dissolved air has a solvent action on lead due to the formation of lead hydroxide a poisonous compound. this Phenomenon is called plumbo solvency
2Pb + O2 + 2H2O →
2Pb(OH)2 16. Mention the uses of
neon?
ü It is used in discharge
tubes and fluorescent bulbs
ü It is used to protect
electrical instrument from high voltage
ü It is used in begcon lights
for safety of air navigation as the light possesses fog.
17. Why HF do not stored in
glass bottle?
It cannot be stored in glass or silica bottles
as it attacks silicates or silica
Na2SiO3
+ 6HF → Na2SiF6 +3H2O
SiO2 + 4HF → SiF4 + 2H2O
18. What is the action of
heat on orthophosphoric acid?
19. H3PO4
is Tribasic acid Prove?
H3PO4
+ NaOH → NaH2PO4 + H2O
H3PO4
+ 2NaOH → Na2HPO4 + 2H2O
H3PO4
+ 3NaOH → Na3PO4 + 3H2O
20. H3PO3
is DiproticWhy?
H3PO3 + NaOH → NaH2PO3
+ H2O
H3PO3 + 2NaOH → Na2HPO3
+ 2H2O
21. Discuss the oxidizing
power of fluorine.
Fluorine is the strong oxidizing agent
It oxidises other halide ions into halogens.
22. How is potash alum
prepared?
Ø Alunite or alum stone K2SO4.Al2(SO4)3.4Al(HO)3
Ø It is finely powered and
boiled with dil H2SO4.
Ø The forming of ammionum
sulphate is combines with potassium sulphate, the alum is crystallized.
23. Write about the Holme’s
signal.
Ca3P + 6H2O →
2PH3↑ + 3Ca(OH)2
CaC2 + 2H2O → C2H2↑
+ Ca(OH)2
24. Why do d-block element
from complexes?
Ø Small size and high
positive charge density.
Ø Presence of vacant (n-1)d
orbital which are of apprpriate energy to accept lone pair of electron from the
ligands for bonding with them.
25. Explain Why d-block
element exhibit variable oxidation states?
Ø Several (n-1)d and ns
electron.
Ø The energies of (n-1)d and
ns orbital are fairly close to each other.
26. Why transition metal
compounds are colored?
Ø The presence of unpaired
electrons
Ø The energy gap between two
energy leaves in the saved subshell being small.
Ø One energy level to another
can be provided by the visible light.
27. What is Philosopher’s
wool? How is it formed?
When Zinc is heated in air at 773K, it burns to form a white
cloud of Zinc oxide which settles to form a wooly flock.
28. What is chrome plating?
Cathode
: The articles to be plated
Anode
: A plate of lead
Electrolyte : chromic acid
+ sulphuric acid
First plated with: Nickel
29. What is spitting of
silver ? How is it prevented?
Molten silver absorbs 20 time its
volume of oxygen which it again expels on cooling .Globules of molten silver
are thrown off .this is called spitting of silver .
Prevention : By covering the molten with a
layer of charcoal.
30. Explain Chromyl
chloride test with equation.
K2Cr2O7
+ 4KCl + 6H2SO4 → 2CrO2Cl2 + 6KHSO4
+ 3H2O
31. Write the action of
aquaregia on gold.
2Au + 9HCl +
3HNO3 → 2AuCl3 + 6H2O +3NOCl
32. What is the action of
heat on copper sulphate crystals?
33. What is Purple of
Cassius? How is it prepared?
Purple of Cassius is colloidal Au + Sn(OH)4
2AuCl3
+ 3SnCl2 → 2Au↓ + 3SnCl4
SnCl4 + 4H2O → Sn(OH)4 +
4HCl
34. State uses of ratio
carbon dating?
ü It is a great tool for
correlating facts of historical importance.
ü It is very useful in
understanding the evolution of life and
fall of civilizations.
35. Explain the principal of hydrogen bonding
Fission → heat + neutrons
3Li6 + 0n1 → 1H3
+ 2He4 + 4.78 MeV
1H2 + 1H3→ 2
He 4 +0n1 + 17.6 MeV
36. What is nuclear fission
reaction?
When lighter nuclear moving
at a high at a high speed are fused to gether to form a heavy nucleus.
1H2 + 1H3→
2 He 4 +0n1 + energy
37. What is ‘Q’ value of a
nuclear reaction?
The amount of energy
absorbed or released during the nuclear reaction.
Q = (mp-mr) 931MeV
mp
- sum of the masses of products
mr - sum of the masses of reactants.
38. What are
super-conductors?
ü Superconductors are ultra
cold substance that conduct electricity without resistance.
ü These materials have
virtually zero electrical resistance.
39. Write a note on
molecular crystal?
ü The lattice points in
molecular crystal consists of
Molecules which do not carry any charge.
ü Diploe –diploe
interaction eg. Ice
ü Vander Waals forces eg. All kinds of molecular Solids.
40. Sketch the s.c, b.c.c
and f.c.c structures
41. Define Bragg’s
equation?
nλ = 2d sinθ
n = order of reflection , λ =
wave length of x-rays
d = interplaner distance in the crystal,θ=
angle of reflection.
42. What is a vitreous
state?
Glassy state or vitreous state is a condition in which certain
substances can exist lying between solid and liquid state.
43. When does entropy
increases in a process?
v In a chemical reaction,
when a number of molecules
of products are more than
the number molecules of reactant
entropy increases.
v In physical process, when a
solid charges to liquid when a liquid to vapour when a solid charges to vapour
entropy increases.
44. What is Gibb ‘s’ free
energy?
G = H - TS
H-enthalpy, T-temperature,
S-entropy.
45. State trouton’s’ rule.
The heat of vaporisation is divided by
the bolling point of the liquid is a constant.
46. Which substance that
deviate from the trouton rule?
v Hydrogen and helium are low
boiling liquids. Their boiling point is slightly greater than 0K.
v Water and alcohol have
intermolecular hydrogen bonding.
So they have high boiling points and
they possess high
∆ Hvap value.
v Acetic acid whose molecules
are partially associated in
vapor phase and possess very low
entropy vaporization which
is very much less than 21
cals/mol/deg.
47. State Lechatelier’s
principle.
If a system at equilibrium is
subjected to a disturbance or stress then the equilibrium shifts in the
direction that tends to nullify the effect of the disturbance or stress.
48. What is reaction
Quotient.
The ratio of the product of initial
concentration of product to products
of initial concentration of reactant
under non- equilibrium conditions.
49. Dissociation of PCl5 Decreases in the presence of
increase in Cl2 Why?
PCl5 ⇌ PCl3+Cl2
Increase of concentraction of Cl2 the equilibrium shift in
the reverse direction ie.,more PCl5 formed and dissociation of PCl5 is decreased.
50.Write a note on parallel
reactions.
The reactions in which one or more
reactants react simultaneously in two or more pathways to give two or more
products are known as parallel reactions.
51. What is activation energy?
Activation Energy =
Threshold Energy - Energy of colliding molecules.
52. Write the Arrhenius
equation and explain the terms?
K=Ae-Ea\RT
K- rate constant, Ea - activation energy,
A-frequency factor, R - gas constant, T-temperature in Kelvin.
53. Define Order of a
reaction
The
sum of power of the concentration of reactants that involved in the rate
equation .
54. Write three example of
opposing reactions.
55. What is heterogeneous
catalysis? Write the examples.
The catalytic process in which the
reactant and catalyst are in the different phases.
56. Write a note about
promoters.
A substance which though itself not a catalyst
it promotes the activity of a catalyst is called a promoter.
Mo – promoter
57. What are catalytic
poison? Give an example
A substance which destroys the activity of
the catalyst poison
As2O3- catalyst poison
58. What is
electrophoresis.
The movement of sol
particles under an applied electric potential.
59. What is active centre?
§ The catalytic surface has
unbalanced chemical bonds on it.
§ These are crowded at the
peaks, cracks and corner of the catalyst.
§ The catalytic activity due to adsorption of
reacting molecules is maximum at these spots.
60.Why is a colloidal system
of gas in gas does not exist?
Gases are completely
miscible and always form true solution.
61. What is brownion
movement?
The continuous
rapid zig-zag ,chaotic random and ceaseless movement executed by a colloidal
particle in the dispersion medium is called
Reason: This is
due to unbalanced bombardment of particle by molecules of dispersion medium.
62. State kohlrausch’s law
At infinite dilution where in the
ionization of all electrolytes is complete each ion migrates independently and
contributes a definite value to the total equivalent conductance of the
electrolyte.
63. What are buffer
solutions?
One which maintains its pH
fairly constant even upon the addition of small amount of acid or base.
e.g
CH3COOH + CH3COONa
64. What is common ion effect?
The reduction of the degree of
dissociation of a salt by the addition of a common ion is called common ion
effect.
AgCl(s)
⇌ Ag +(aq) Cl-(aq)
NaCl is added to the AgCl solution. Here
Cl- ion is act as a common ion. So the dissociation of
AgCl is decreased.
65. State ostwald’s
dilution law
Ostwald’s dilution law relates the
dissociation constant of the weak electrolyte with the degree of dissociation
and the concentration of the weak electrolyte.
66. Define Faraday first
and second law of electrolysis?
FIRST LAW:-
The mass of the substance liberated at
the electrodes during the electrolysis is directly proportional to the quantity
of electricity that passes through the electrolyte.
SECOND LAW:
When the same quantity of electricity
passes through solution of different electrolytes the amount of substances
liberated at electrodes are directly proportional to chemical equivalent.
67. What are the condition
for optical isomerism?
*The compounds should contain Asymmetric (or)
chiral carbon atom.
*The compounds should have non-super
imposable object and mirror image configuration.
68. Why meso tartaric acid
is an optically in active compound with chiral carbon atom?
*Two Asymmetric carbon atom the
confiaguration of one carbon is the mirror image of the other is laevo
rotatory.
*Symmetric plane divides
the molecule into equal halves.
*super-imposable on its mirror image.
69. Difference between
Racemic from and Meso from.
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Racemic
from
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Meso from
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1. It is a mixture that can be
separated into two optically Active froms
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It is a single compound and hence
cannot be Separated
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2. Optically inactive due to
External compensation
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optically inactive due to . Internal compensation
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3. Molecules are chiral
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Molecules are achiral
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70. Define racemic mixture?
Give an example.
ü It is a mixture that
contains equal amount of d-isomer and
l-isomer.
ü Optically inactive form due
to external compensation.
e.g. Equal amount of d and l tartaric
acid.
71. What are chromophores?
Give two example.
An organic compounds appears colored due
to the presence of certain unsaturated groups (the groups with multiple bonds)
in it.
e.g. Nitro, Azo.
72. Why iodoform and
phenolic solutions are called antiseptic?
Iodoform , CHI3 is used an
antiseptic and its solutions 1% solutions is disinfectant.
0.2percent solution of
phenol acts as an antiseptic and its 1% solution is a disinfectant.
73. Give any three
characteristics of dye?
ü A dye should have a
suitable colour.
ü It should be able to fix it
self or be capable of being fixed to the fabric.
Resistant to the action of
water, dilute acids and alkalies.
74. Write a note on anti
oxidants.
The substance that act against oxidants
are called antioxidants.
e.g.
Vitamin - C, vitamin - E
75. What is antipyretics?
Lowering the body temperature to the
normal
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S.Prabakar,M.Sc,M.Phil,B.Ed,PGDCA,
PG Asst In Chemistry,
E.R.K Higher Secondary School,
Pappireddipatti, Dharmapuri.
Cell: 9843082238 E.Mail:prabakar.che@gmail.com
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