HCS Previous Year Optional Paper 2003: Chemistry Frontier IAS
Baljit Dhaka
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HCS Previous Year Optional Paper 2003: Chemistry Frontier IAS

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HCS Mains Optional Paper Chemistry-2003

HCS Previous Year Optional Paper 2003: In this post, we will talk about Hcs mains 2003 previous year Chemistry optional paper.

Time: 3 hours                                                                                                                                        Marks- 150

Note: Attempt five questions in all. All questions carry equal marks. Q. No.l is compulsory. Answer two questions from Part l and two questions from Part ll. The parts of the same question must be answered together and must not be interposed between answers to other questions.

1. Write critical notes on any four of the following:    4X 7.5 =30 Marks
(a) Explain bonding in Ni(CO)4, [Fe(CN)6]4- and [Co(NH3)6]3+using valence bond approach. 
(b) Imperfections in crystals. 
(c) Application of second law of thermodynamics in relation to the entropy changes in an ideal gas. 
(d) Mechanism of Reimer-Tiemann reaction
(e) Factors which stabilize carbanion and the methods of generation of carbanions. 
(f) Chemical shift and coupling constant. 


2. (a) Write the electronic configuration of O2- and molecular orbital representation of He2+.

(b) Draw the d-orbital splitting pattern for a transition metal ion in a tetrahedral complex. 

(c) Write the reduction of  KMnO4 in acidic, neutral, and alkaline media and also determine the ratio of changes in the oxidation state of Mn in these three media. 30 marks

3. (a) Half-life period of a chemical reaction is 50 minutes. The half-life period of the reaction is doubled on doubling the concentration of the reactant. Calculate the order of the reaction. 

(b) Calculate the molecular translational of partition function for I mole of nitrogen gas at 270c and I atm assuming the gas to behave ideally ( given h= 6.625 x 10-27 erg sec and K = I.3 x 10-16 erg deg-1.

(c) (i) Derive the following expression for the change in entropy of an ideal gas: 

(ii) Explain reasons for high and low quantum yield reactions. 30 marks 


(b) How will you calculate bond order in CO Molecule with the help of molecular orbital theory? Explain also the negligible dipole moment of the molecule with this theory. 

(c) (i) Give the resonance structure of 
(ii) Explain the term Chemical Potential? Obtain an expression for the variation of chemical potential with temperature.       30 marks 


5. (a) Explain Kinetic and thermodynamics control of products in elimination reactions with suitable examples. 

(b) Write the stereoelectronic requirements of Beckmann rearrangement. Discuss the mechanism of this reaction with suitable examples and describe its synthetic importance.

(c) Draw an orbital picture to account for the Claisen arrangement. 30 marks 

6. (a) Complete the following reaction by writing the intermediates and final products: 

(b) How do the IR spectra of the following compounds differ?

(c) Explain number and weight average molecular weight of polymer. Describe viscosity measurement methods to determine molecular weight of polymer. 30 marks

7. (a) Describe preparation and properties of polystyrene and Teflon. 

(b) Explain the following: 
(i) Singlet and Triplet states in electronic spectra. 
(ii) Woodward-Fieser Rules 
(iii) Isotope effect and its applications

(c) Describe the principles of NMR and discuss the application of HNMR to simple organic molecules.   30 marks