Saturday, September 09, 2017

Dibrugarh University Question Papers: Chemistry (Physical, Inorganic and Organic)' 2016

2016 (November)
CHEMISTRY
(Major)
Course: 101
(Physical, Inorganic and Organic)
(Both New/Old Course)
Full Marks: 80
Pass Marks: 32 (Backlog) / 24 (2014 onwards)
Time: 3 hours
The figures in the margin indicate full marks for the questions
SECTION – A
(Physical Chemistry)
(Marks: 26)

1. Choose the correct answer of the following: 1x3=3

  1. Amorphous substances are isotropic because
  1. They have same value of any property in all directions.
  2. They have different values of physical properties in different directions.
  3. They have definite geometrical shape.
  4. None of the above.
  1. The reciprocal of viscosity is called
  1. Surface tension.
  2. Frictional resistance.
  3. Fluidity.
  4. None of the above.
  1. At 27the kinetic energy of two moles of is
  1. 7482.6 J
  2. 3741.3 J
  3. 2494.2 J
  4. 0
2. Answer any three questions from the following: 2x3=6
  1. Explain why we have to define the heat capacities of gases under constant pressure and constant volume conditions.
  2. Find the interplanar distance in a crystal in which a series of planes produces a first-order reflection from a copper X-ray tube at an angle of.
  3. Calculate the most probable velocity of nitrogen molecules at 15
  4. Surface tension of a liquid vanishes at tis critical temperature. Explain.
  5. What is parachor? The parachor value of ethane is 99.5 and that of group is 39. From this, calculate the parachor value of double bond.
UNIT – I
Answer any two questions from the following: 3 ½ x 2=7
3. (a) Deduce the reduced equation of states from van der Waals’s equation of states and define the law of corresponding states from it. 1 ½ + 1 = 2 ½
(b) Define Boyle’s temperature. 1
4. Deduce the relationship for calculation of collision diameter of a gas molecule from the measurement of viscosity of the gas. 3 ½
5. (a) With the help of kinetic gas equation, deduce Boyle’s law. 2
(b) Show that 1 ½
UNIT – II
Answer any one question from the following: 3
6. Describe the laboratory method for determining the surface tension of a liquid. 3
7. (a) Write the difference between nematic and smectic liquid crystals. 2
(b) Give two examples of non-Newtonian liquids. 1
UNIT – III
Answer any two questions from the following: 3 ½ x 2 = 7
8. State the law of rational indices. What are Miller indices? A crystal plane intersects the three crystallographic axes at the multiples of unit distance 3/2, 2 and 1. Find the Miller indices of the plane. 1+1+1 ½ = 3 ½
9. Discuss Schottky defects and Frenkel defects or crystal giving examples. What is F-centre? 3+½ = 3 ½
10. Define unit cell. What parameters are used to describe a particular system or crystal? Name the seven crystal systems. Which of them is the most symmetrical and which one is the most unsymmetrical? ½ + 1 + 1 + 1 = 3 ½

SECTION – B
(Inorganic Chemistry)
(Marks: 27)

11. Choose the correct answer of the following: 1x3=3
  1. Electron affinity values of C, Si, Ge and Sn are given below. Which of the following corresponds to silicon?
  1. Number of unpaired electron present in NO molecule is
  1. Three.
  2. Two.
  3. One.
  4. Zero.
  1. Which of the following molecules has the smallest bond angle?
  1. BeF2
  2. SF6
  3. BF3
  4. NH3
12. Answer the following questions: 2x3=6
  1. First, second and third ionization energy of boron atom are, and. Explain these values.
  2. What are bond orders? What will be the bond order of?
  3. The bond angles of PF3, PCI3, PBr3 and PI3 are 97.80, 100.30, 101.50 and 1020 respectively. Explain.
13. Answer any two questions from the following: 3x2=6
  1. How was the term ‘electronegativity’ defined by Allred and Rochow? Calculate the electronegativity of silicon using Allred-Rochow equation (covalent radius of silicon is ) 1+2=3
  2. Using Slater’s rule, calculate the effective nuclear charge for the following: 1x3=3
  1. A 3d-electron in manganese atom.
  2. A 4s-electron in cobalt atom.
  3. At the periphery of Fe2+
  1. Explain the following giving reasons: 1½ x 2 = 3
  1. The ionization energy of A1 to form A1+ ion is less than that of Mg to form Mg+ ion.
  2. Second electron affinity of an element is always endothermic.
14. Answer any three questions from the following: 4x3=12
(a) (i) N2 molecule is more stable than NO molecule. Explain on the basis of molecular orbital theory. 2
(ii) Compare bond length and magnetic properties of and species with the help of molecular orbital theory. 2
(b) What is lattice energy of crystals? Draw Born-Baber cycle for the ionic solid and show how the lattice energy can be computed with its help. 1+3=4
(c) Using VSEPR theory, predict the structures of, , and . 2
(d) (i) What is meant by covalent ionic resonance? Illustrate it with a suitable example. 2
(ii) Write a note on bonding and anti-bonding molecular orbital. 2


SECTION – C
(Organic Chemistry)
(Marks: 27)

15. Choose the correct answer of the following: 1x3=3
  1. What is the order of stability of the following carbanions?

D:\Logo\Sun Mun\1.jpg


  1. IV > II > III > I
  2. I > III > II > IV
  3. I > II > III > IV
  4. II > III > IV > I
  1. Which of the following molecules has the shortest carbon – carbon bond?
  1. CH3 – CH2 – CH3
  2. CH3 – CH = CH2
  3. CH3 – C CH

  4. CH2 = CH – CH = CH2
  1. What is the major product of the following reaction?D:\Logo\Sun Mun\2.jpg

16. Answer any four questions from the following: 1½ x 4 = 6
  1. Vinyl halides have low reactivity towards nucleophilic substitutions. Explain.
  2. Identify the electrophiles and nucleophiles from the following:
  3. Define benzyne. How is it generated? Give one chemical reaction of benzyne.
  4. The pKa value of phenol is 10 and that of cyclohexanol is 16. Explain this observation.
  5. Explain why dipole moment of CHCI3 is less than that of CH2CI2.
17. Answer any three questions from the following: 2x3=6
  1. Identify the following reactions as kinetically controlled and thermodynamically controlled:


D:\Logo\Sun Mun\3.jpg

Draw the energy-profile diagram for the above reactions.
  1. Alkyl groups attached to the benzene ring have effect in the order:
  1. Two compounds I and II are given below. Which one of them is more basic and why?

D:\Logo\Sun Mun\4.jpg


  1. Singlet carbine adds to alikeness in a stereospecific manner whereas triple carbenes do not. Explain with example.
  2. What do you understand by the term ‘resonance’? Write two conditions necessary for resonance.
18. Answer any six questions from the following: 2x6=12
  1. Label the following compounds with R and S configurations:



;

  1. Draw the three stereoisomers of tartaric acid in Fischer’s projection. Which of them are enantiomers and which one is the meso form?
  2. Draw the geometric isomers of 2-mythel cyclopropane carboxylic acid given below:


Which of them are optically active? Draw their enantiomers as well.
  1. Write a short note on geometrical isomerism due to C=N – bond with examples.
  2. Draw the Fischer’s projection formula for the following:
  1. (R)-3-methylpentan-1-ol
  2. (S)-2,3-demethyl hexane.
  1. The presence of chiral centre in an organic compound is neither a necessary nor a sufficient condition for showing enantiomerism. Explain.
  2. You are given a racemic alcohol and a pure optically active organic base brucine. How would you proceed to resolve the alcohol? Explain the principle.
  3. Write a note on either asymmetric synthesis or Walden inversion.
***

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