RGU Question Paper Chemistry Semester II 2021: Physical, Inorganic and Organic Chemistry (Old)

 JUNE – 2021

B. Sc. (II Semester) Examination

CHEMISTRY

Paper: CHEM-121 (Old Course)

(Physical Inorganic and Organic Chemistry)

Full Marks : 50

Pass Marks : 35%

Time : Two Hours

Note: (i) Answer all the questions.

(ii) The figures in the margin indicate full marks for the questions.

1. Answer all the questions: 2x5= 10

(a) Show that the radius ratio of cation to anion in octahedral crystal is 0.414.

(b) Why does the reaction stop at equilibrium?

(c) Explain the shape of XeF6 on the basis of VSEPR theory.

(d) Cyclopentadienyl anion is aromatic while the corresponding cation is not? Explain why?

(e) How will you distinguish between benzyl chloride and chlorobenzene?

2. Answer any five questions: 3x5 = 15

(a) A unit cell of sodium chloride has four formula units. The edge length of unit cell is 0.564 nm. Calculate the density of sodium chloride.

(b) A mixture of N2 and H2 in a proportion of 1:3 by volume was subjected to a pressure of 30 atm and a temperature 723k. At equilibrium the mixture contained 6% of NH3 by volume. Calculate Kp.

(c) In Nacl ionic crystal bond length is 2.36 Ȧ and the experimental dipole moment is 8.5D. Calculate the % ionic character in Nacl.

(d) What is Friedel-craft acylation reaction? Give the mechanism of the reaction.

(e) Explain why is –NH2 group ortho-para directing but –NO2 is meta directing group.

(f) Write the following conversions:

(i) Ethyl alcohol to n-butane

(ii) Propene to 1-bromobropane

3. Answer any five questions: 5x5= 15

(a) Define the terms viscosity and viscosity coefficient. How viscosity of a liquid is determined by using Ostwald viscometer.

(b) What is law of mass action? Derive an expression for the equilibrium constant Ke for the reaction H2+I2 ═ 2HI.

(c) What do you mean by inter-molecular and intramolecular hydrogen bonding? What are the consequences of hydrogen bonding?

(d) What happens when (write chemical reactions only): 1x5= 5

(i) Acetylene is passed through red hot Fe tube

(ii) Phenol is heated with Zn dust.

(iii) Benzene reacts with n-propyl chloride in presence of anhydrous Alcl3

(vi) N-heptane is heated at high temperature and pressure in presence of Cr2O3/V2O5

(vii) Benzene reacts with acetyl chloride in presence of anhydrous Alcl3

(e) Complete the following reactions: 1x5= 5

(f) (i) What are the differences between Sn1 and SN2 reaction of alkyl halide?

(ii) Haloarenes are less reactive than halo alkanes towards nucleophilic substitution reaction. Give reason.