M.Sc. (Semester IV) (CBCS) Examination Mar/Apr-2018
Physical Chemistry
CHEMICAL KINETICS
Time: 2½ Hours
Max. Marks: 70
Instructions: Attempt five questions. Section I is compulsory. Attempt any two questions from Section II and any two questions from Section III. Answer to all 5 question (Section II and III) should be written in the one answer book. All question carry equal marks. Figures to the right indicate full marks. Use of log tables and calculators is allowed.
Section I
Q.1
Answer the following.
14
Can one determine the rate law only from knowledge of the stoichiometry of a reaction?
What is a reversible first-order reaction?
What is the Arrhenius equation?
What is the relationship between the equilibrium constant and the rate constants?
What are the initiation, propagation, inhibition and termination steps in a chain reaction?
Which one of the following is NOT a key concept of the collision theory?
Particles must collide in order to react
Particles must move slowly when they collide, otherwise they simply "bounce off" one another
Particles must collide with the proper orientation
Particles must collide with sufficient energy to reach the activated complex in order to react.
The minimum amount of energy required to convert the reactants into the activated complex is known as
If minimum potential energy of reactants is less than that of products, the reaction will be
What is an enzyme-catalyzed reaction?
The reaction 2NO+Br2→2NOBr follows the mechanism given below.
NO+Br2→NOBr2…….fast
NOBr2+NO→2NOBr……slow If concentration of both NO and Br2 are increased two times the rate of reaction would become
4 times
6 times
16 times
8 times
A reaction in which all reactants are in the same phase is called
Elementary
Bimolecular
Homogeneous
Heterogeneous
In the rate law, Rate O2 the reaction is order for NO, order for O2, and order overall.
Second; first; third
Second; zero; third
First; second; third
First; third; first
Page 2 of 2
SLR-UF-224
Which one of the following is not a biological catalyst?
Washing powder enzymes
Catalase
Yeast
Hydrogen peroxide
Which of the following would NOT increase the rate of reaction?
Raising the temperature
Increasing the concentration of reactants
Increasing the volume of the container for a gaseous reaction
Increasing the surface area of a solid reactant
Section II
Q.2
Discuss in detail about the collision theory of bimolecular reaction.
07
What do you understand by the term "rate determining step" of a complex reaction? What is steady-state hypothesis?
07
Q.3
The gas phase reaction 2A→B+C is bimolecular with the activation energy of 24000 cal mol−1. The molecular weight and diameter of A are respectively 60 and 3.5 Å. calculate from collision theory the specific rate constant for the decomposition at 27°C
07
Derive the rate law for the formation of hydrogen bromide from H2 and Br2.
07
Q.4
The rate constant of a second order gas reaction H2+I2=2HI is 0.0234 1 mol−1sec-1at 400 °C and the activation energy is 150 kJ mol−1. Calculate ΔH0+ and ΔS0+ of the reaction.
07
What is enzyme catalysis? Derive Michaelis Menton equation for enzyme catalysed reaction.
07
Section III
Q.5
Discuss the kinetics of opposing reactions.
05
Explain, with examples, the functions of catalytic promoters and poisons in chemical reactions.
05
H3O+ acts as a homogeneous catalyst in the reaction of inversion of Sucrose. At pH=3 the reaction in aqueous solution proceeds with a constant half-life of 50 minutes. What value of the half-life would you expect at
04
Q.6
Write a short note on Lineweaver and Eadie plots.
05
Explain salt effects in ionic reactions.
05
At 25°C and pH the turnover numbers and Michaelis constants for the fumarase reaction
Fumarate+ L-malate
are K3=0.20×103s−1,K2=0.60×103s−1,Ks=7.0×10−6 mol L−1,Kp=100×10−6 mol L−1. What are the values of K1 and K4 and the equilibrium constant
04
Q.7
Write a note on any Three of the following.
14
Branching chain reactions explosion limits
Autocatalysis
Partition functions and activated complex
Saddle point