Chemical Kinetics Questions PDF

1. What is meant by the "rate of reaction"? * A) The time it takes for a reaction to complete. * B) The change in concentration of a reactant or product per unit time. * C) The amount of product formed in a reaction. * D) The speed at which reactants are mixed. 2. What are the units of rate of reac...

1. What is meant by the "rate of reaction"? * A) The time it takes for a reaction to complete. * B) The change in concentration of a reactant or product per unit time. * C) The amount of product formed in a reaction. * D) The speed at which reactants are mixed. 2. What are the units of rate of reaction? * A) s * B) mol dm-3 * C) mol dm-3 s-1 * D) dm3 mol-1 s-1 3. What is meant by the "order of reaction" with respect to a particular reactant? * A) The power to which the concentration of that reactant is raised in the rate equation. * B) The stoichiometric coef cient of that reactant in the balanced chemical equation. * C) The number of molecules of that reactant involved in the reaction. * D) The position of that reactant in the rate equation. 4. If a reaction is rst order with respect to reactant A, what happens to the rate if the concentration of A is doubled? * A) The rate stays the same. * B) The rate doubles. * C) The rate triples. * D) The rate quadruples. 5. If a reaction is second order with respect to reactant B, what happens to the rate if the concentration of B is doubled? * A) The rate stays the same. * B) The rate doubles. * C) The rate triples. * D) The rate quadruples. 6. If a reaction is zero order with respect to reactant C, what happens to the rate if the concentration of C is doubled? * A) The rate stays the same. * B) The rate doubles. * C) The rate triples. fi fi * D) The rate quadruples. 7. What is the overall order of a reaction? * A) The order of the slowest reactant. * B) The order of the fastest reactant. * C) The sum of the orders with respect to each reactant in the rate equation. * D) The difference between the orders of the reactants and products. 8. The rate equation for a reaction is: rate = k[A][B]2. What is the overall order of the reaction? * A) 1 * B) 2 * C) 3 * D) 4 9. What is the symbol for the rate constant? * A) r * B) k * C) K * D) R 10. What are the units of the rate constant, k, for a rst-order reaction? * A) mol dm-3 s-1 * B) s-1 * C) dm3 mol-1 s-1 * D) dm6 mol-2 s-1 11. What are the units of the rate constant, k, for a second-order reaction? * A) mol dm-3 s-1 * B) s-1 * C) dm3 mol-1 s-1 * D) dm6 mol-2 s-1 12. For the reaction X + 2Y → Z, the rate equation is: rate = k[Y]2. Which species appear in the rate-determining step? * A) 1 molecule of X * B) 2 molecules of X * C) 1 molecule of Y fi * D) 2 molecules of Y 13. What is the rate-determining step in a multi-step reaction? * A) The fastest step * B) The slowest step * C) The rst step * D) The last step 14. What is the relationship between the rate equation and the stoichiometry of the overall balanced equation? * A) they must be identical * B) there is no direct relationship * C) the rate equation can be worked out from the stoicheometry * D) the rate equation gives half the stoicheometry 15. If a reaction involves several steps, the rate equation includes: * A) the reactants in the fastest step * B) the reactants in the slowest step * C) all the reactants * D) only the products 16. What does the Arrhenius equation describe? * A) The relationship between the rate constant and temperature. * B) The relationship between the rate of reaction and concentration. * C) The relationship between the order of reaction and the rate constant. * D) The relationship between the activation energy and the rate of reaction. 17. What is the symbol for activation energy in the Arrhenius equation? * A) A * B) Ea * C) R * D) T 18. What are the units of activation energy (Ea) in the Arrhenius equation? * A) K * B) mol dm-3 * C) J mol-1 fi * D) s-1 19. What is the symbol for the gas constant in the Arrhenius Equation? * A) A * B) Ea * C) R * D) T 20. What are the units of the gas constant, R? * A) J mol-1 K-1 * B) J mol-1 * C) K * D) mol dm-3 21. What is the symbol for the pre-exponential factor (frequency factor) in the Arrhenius Equation * A) A * B) Ea * C) R * D) T 22. What is the Arrhenius equation? * A) k = Ae-Ea/RT * B) k = AERT * C) k = AeRT/Ea * D) k = A + Ea/RT 23. What is the logarithmic form of the Arrhenius equation? * A) ln k = ln A + Ea/RT * B) ln k = ln A - Ea/RT * C) ln k = ln(A - Ea/RT) * D) k = ln(A/EaRT) 24. When plotting a graph of ln k against 1/T, what does the gradient represent? * A) -A * B) -Ea/R * C) Ea/R * D) ln A 25. When plotting a graph of ln k against 1/T, what does the y-intercept represent? * A) -A * B) -Ea/R * C) Ea/R * D) ln A 26. As temperature increases, what happens to the rate constant, k? * A) It decreases. * B) It stays the same. * C) It increases. * D) It depends on the reaction. 27. As activation energy (Ea) increases, what happens to the rate constant, k? * A) It decreases. * B) It stays the same. * C) It increases. * D) It depends on the reaction. 28. How does a catalyst affect the activation energy of a reaction? * A) It increases it. * B) it decreases it * C) it doesn't affect it * D) depends on the type of catalyst 29. How does a catalyst affect the rate constant,k, of a reaction? * A) It decreases k. * B) It has no effect on k. * C) It increases k. * D) It depends on the reaction. 30. The gradient of an Arrhenius plot (ln k vs 1/T) is -10000 K. The gas constant, R, is 8.314 J mol-1 K-1. What is the activation energy, Ea? * A) -83140 J mol-1 * B) 83140 J mol-1 * C) -1203 J mol  User con nue ti WJEC Okay, I missed a nal calculation from question 30, here is the correction: 30. The gradient of an Arrhenius plot (ln k vs 1/T) is -10000 K. The gas constant, R, is 8.314 J mol-1 K-1. What is the activation energy, Ea? * A) -83140 J mol-1 * B) 83140 J mol-1 * C) -1203 J mol-1 * D) 1203 J mol-1 Answers and Explanations: 1. B) The change in concentration of a reactant or product per unit time. - This is the de nition of rate of reaction. 2. C) mol dm-3 s-1 - These are the standard units. fi fi 3. A) The power to which the concentration of that reactant is raised in the rate equation. - This is the de nition of order with respect to a reactant. 4. B) The rate doubles. - For a rst-order reaction, rate is directly proportional to concentration. 5. D) The rate quadruples. - For a second-order reaction, rate is proportional to the square of the concentration. 6. A) The rate stays the same. - For a zero-order reaction, rate is independent of concentration. 7. C) The sum of the orders with respect to each reactant in the rate equation. - This is how overall order is determined. 8. C) 3 - 1 (from [A]1) + 2 (from [B]2) = 3 9. B) k - This is the standard symbol. 10. B) s-1 - These are the units for a rst-order rate constant. 11. C) dm3 mol-1 s-1 - These are the units for a second-order rate constant. 12. D) 2 molecules of Y - The rate equation only involves Y, and the power is 2. 13. B) The slowest step - The slowest step determines the overall rate. 14. B) there is no direct relationship Correct de nition. 15. B) the reactants in the slowest step Correct de nition. 16. A) The relationship between the rate constant and temperature. - The Arrhenius equation shows this relationship. 17. B) Ea - This is the symbol for activation energy. 18. C) J mol-1 - These are the standard units. fi fi fi fi fi 19. C) R - This is the symbol. 20. A) J mol-1 K-1 - These are the units for the gas constant. 21. A) A This is the symbol. 22. A) k = Ae-Ea/RT - This is the correct Arrhenius equation. 23. B) ln k = ln A - Ea/RT - This is the logarithmic (linear) form. 24. B) -Ea/R - The gradient of the line is -Ea/R. 25. D) ln A - The y-intercept is ln A. 26. C) It increases. - Increasing temperature increases the rate constant. 27. A) It decreases. - A higher activation energy means a slower rate (smaller k). 28. B) it decreases it A catalyst lowers the activation energy. 29. C) It increases k. - Lowering Ea increases the value of k. 30. B) 83140 J mol-1 - Gradient = -Ea/R; -10000 K = -Ea / 8.314 J mol-1 K-1; Ea = 83140 J mol-1 Powered by pmfm.ai Request Support