NATIONAL OPEN UNIVERSITY OF NIGERIA
University Village, Nnamdi Azikiwe Expressway, Plot 91, Cadastral Zone, Jabi, Abuja
FACULTY OF SCIENCES
DEPARTMENT OF PURE AND APPLIED SCIENCE
JULY 2018 EXAMINATION QUESTIONS
COURSE CODE: CHM 407
COURSE TITLE: Reaction Kinetics
COURSE UNIT: 2 units
TIME: 2 hours
INSTRUCTION: Answer Question one (1) and any other three (3) questions
Question 1
(a) State the following laws of photochemistry
i. Draper-Grothus law (1 mark)
ii. Stark-Einstein law (1 mark)
(b) Define the under listed types of catalysis and give one example (equations are required) for each
i. Heterogeneous catalysis (2 marks)
ii. Homogenous catalysis (2 marks)
iii. Enzyme catalysis (2 marks)
(c) In photochemical decomposition of acetone using 313 nm light, 7.57 x 10-6 mol of carbon monoxide is formed in 20 minutes. If the light absorbed corresponds to 2.41 x 10-3 Js-1, calculate the energy absorbed per quantum of the photon . (3 marks)
(d) The decomposition of HI is a second order reaction. At 700 K, the rate constant for the reaction is 1.8 x 10-3 M/s. If the initial concentration of HI is 0.002 M.
Answer the following,
(i) Write a balance equation for the decomposition (1 ½ marks)
(ii) Write an expression for the rate law showing the relationship between rate and order of
reaction (1 ½ marks)
(iii) Calculate the rate of the reaction and express your answer in appropriate unit (2 marks)
(e) Define the term, molecularity of a reaction (2 marks)
(f) Write equations for the half-life of a first and second order reaction (2 marks)
(g) What is a pseudo first order reaction/ (2 marks)
(h) What are catalyst poison, promoters and inhibitors (3 marks)
Question 2
(a) Given the reaction, 2N2O5 = 4NO2 + O2, write an expression for the theoretical rate equation with respect to the reactant and the products. (3 marks)
(b) In writing theoretical rate equation in ‘a’ above, positive and negative signs were involved. Give reason for the choice of the sign (2 marks)
(c) Derive an integrated rate law for a zero order reaction (5 marks)
(d) The decomposition of hydrogen iodide on gold at 323K is zeroth order reaction and the rate constant is 1.20 × l0-4 Ms-1 a) If the initial concentration of hydrogen iodide is 0.500M. Answer the following questions
i. calculate its concentration after 3.00 × 103s. (2 marks)
ii. How long will it take for all of the hydrogen iodide to decompose? (3 marks)
Question 3
(a) What are the factors that influence the adsorption of gases on a solid surface (3 marks)
(b) State three basic assumption of the Langmuir adsorption isotherm (3 marks)
(c) Write the Langmuir and Freundlich adsorption equation and highlight the nature of graph expected for each of them. (6 marks)
(d) Highlight three differences between physical and chemical adsorption (3 marks)
Question 4
(a) Write down the Arrhenius equation relating the rate constant k and the activation energy Ea. Explain each term used in the equation. (3 marks)
(b) A rate constant of a chemical reaction is 1.78 x 10-4 Lmol-1s-1 at 40 °C and 1.38 x 10-3 Lmol-1s-1 at 80 °C. Evaluate the activation energy for the reaction. (7 marks)
(c) What is a chain reaction and what are the steps involves in a typical chain reaction? (3 marks)
(d) With the aid of suitable equation, explain how Br2 molecule can be activated to initiate a chain reaction (2 mark)
Question 5
(a) Kinetic data for the reaction, Cl2 + 2NO = 2NOCl are presented in the Table below. Answer the questions that follows:
[Cl2]0/M
[NO]0/M
Initial rate/Ms-1
0.10
0.10
3.0 × 10-3
0.20
0.10
6.0 × 10-3
0.20
0.20
2.4 × 10-2
i Use the above information to calculate the order of the reaction (11 marks)
ii. Calculate the rate constant of the reaction (2 marks)
(b) What is meant by molecularity (2 marks)
You can get the exam summary answers for this course from 08039407882
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