LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – CHEMISTRY

GH 57

THIRD SEMESTER – APRIL 2008

CH 3801 – CHEMICAL KINETICS

 

 

 

Date : 28-04-08                  Dept. No.                                        Max. : 100 Marks

Time : 1:00 – 4:00

 

PART – A

Answer All the questions:                                                                 (10×2=20)

 

1. Define time order. How is it different from true order?
2. For a reaction of the type A + B ®  products on doubling the concentration of ‘A’ alone, rate is doubled. On doubling both A and B, rate increases eight times. Deduce the total order of the reaction.
3. What is the effect of ionic strength on the rate constant of the reaction in solution?

1. Write down the expression for the rate constant of a reaction between two linear molecules forming a non-linear activated complex on the basis of ARRT.
2. What is electrostriction?
3. Define Stern-Volmer constant.
4. Mention any four relaxation techniques used for the study of kinetics of fast reactions.
5. What is capillary condensation?
6. What are van’t  Hoff intermediates?
7. Mention the significance of Hammett acidity function.

 

PART – B

Answer any EIGHT questions:                                                        (8×5=40)

 

1.  Explain the need for “potential energy surface”.
2. How is order of a reaction determined using dimensionless parameters?
3. The rate constant for the second order neutralisation of 2-nitropropane (A) by     base (B) in aqueous solution is given by the expression

 

log₁₀k  = –

The time is in minutes while the concentrations are in mol/lit. Calculate the energy of activation in cal/mol and the half life penod at 10°C when the initial concentration of each reactant is 0.008M.

1.  The rate constant of a second order gas phase reaction is 8.1 ´10⁴ M^-1 s^-1 at 331°C with  Calculate for the reaction.
2. How is volume of activation for a reaction in solution determined experimentally? Mention its significance.
3. Outline the importance of Hammett linear free energy relation.
4. Explain Skrabal plots.
5. How is surface area of a solid determined using multilayer adsorption studies.
6. For the weak base 2- nitro anilene (B) in 0.02M HClO₄ the ratio of (BH⁺) to (B) is 0.01. Calculate

1. i) _pk_BH⁺ for 2-nitro anilinium ion and
2. ii) the ratio of (BH⁺) to (B) in 0.05M HClO₄ using the same indicator.

 

1. Derive an expression for relaxation time for a I order reaction.
2. Explain Bronsted- catalytic law.
3. Write down all the steps involved in the thermal decomposition of acetaldehyde with the relevant rate expression for each step of the chain reaction.

 

PART – C

Answer any FOUR  questions:                                                        (4×10=40)

 

1. Explain the kinetics of unimolecular gas phase reactions with relevant derivations.
2. Explain the double sphere model for the influence of dielectric constant on the rate of an ion-ion reaction in solution.
3. In the Kinetic study of the Oxidation of N-ethyl anilene(S) by peroxomono sulphuric acid (O) the following results were obtained.

1. The reaction follows I order kinetics with respect to each
2. The rate decreases with decreasing [H⁺]

• Addition of LiClO₄ (aq) has no effect on the rate

1. is found to be negative.

Interpret these observations and suggest a suitable mechanism with the rate expression.

1. Discuss the kinetics of bimolecular surface reactions with the relevant mechanisms and rate laws.
2. Explain any two of the following

1. Stern – Volmer equation
2. Hammett acidity function
3. Flash photolysis
4. Evaluation of k_H⁺ for a specific hydrogen ion catalysis.

1. a) Derive an expression for rate constant of a I order parallel reaction and explain

1. b) Explain the mechanism of single substrate enzymatic reaction.

 

Go To Main page

Latest Govt Job & Exam Updates:

View Full List ...