Thursday, 26 February 2015

12th Chemistry Study Material


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
1.A particle is localized in space
A wave is delocalized in space
2.Particle do not interfere
wave can interfere
3.Total number of particle in a space is equal to their sum.            
The resultant wave can be larger or smaller then the individual wave.
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 + 0n11H3 + 2He4 + 4.78  MeV
1H2 + 1H32 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 + 1H32 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- 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.
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?
      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.
    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.
Racemic from 
Meso from
1. It is a mixture that can be separated into two optically Active froms                    
It is a single compound and hence cannot be Separated            

2. Optically inactive due to External compensation                      

optically inactive due to .                       Internal compensation
3. Molecules are chiral
Molecules are achiral

70. Define racemic mixture? Give an example.
ü It is a mixture that contains equal amount of d-isomer and
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
PG Asst In Chemistry,
E.R.K Higher Secondary School,
Pappireddipatti, Dharmapuri.
Cell: 9843082238
                         e.g. Aspirin , antipyrine.

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