Chemical kinetics is crucial in board and competitive exams because it quantitatively links reaction rate with concentration through order, rate laws, and integrated rate equations. It also tests deeper concepts like reaction mechanisms, steady-state and pre-equilibrium approximations, and the temperature dependence of rate constants via Arrhenius theory—skills that frequently appear in both numericals and conceptual MCQs.
20
Minutes
15
Questions
1 / -0
Marking
Q1. For the first-order decomposition products with rate constant and initial concentration , the time required for to fall to is:
Q2. A reaction follows rate law . In one experiment with the concentration falls to in . If the reaction is repeated with , the time required for to fall to is:
Q3. Consider the mechanism
(1) (fast equilibrium)
(2) (slow).
Using the pre-equilibrium approximation, which of the following rate expressions for formation of is predicted?
Q4. For the bimolecular reaction with rate law , is kept in large excess so that pseudo-first-order kinetics applies. When the half-life of is ; when the half-life of is . The true bimolecular rate constant is:
Q5. A first-order reaction has half-life at and at . Assuming Arrhenius behaviour , estimate the activation energy (in kJ mol). Use .
Q6. A first-order reaction A → products has a half-life . If the initial concentration is , what is after ? (Use and .)
Q7. Initial rate data for a reaction are: Exp(1) ; Exp(2) ; Exp(3) . If the rate law is , determine and the initial rate when .
Q8. For the bimolecular reaction products the rate law is with . If and and is in large excess (so ), how long will it take for to decrease to of its initial value? (Treat this as pseudo-first-order with .)
Q9. Consider the mechanism: (1) , (2) , (3) . Given , , and initial concentrations , use the steady-state approximation for (with ) to calculate the initial rate .
Q10. A radical chain mechanism proceeds by: Initiation at constant rate , Propagation , Termination . Assuming steady state for and that initiation yields two radicals per initiation, one obtains and . Given , , and , what is the rate of product formation ?
Q11. For a first-order reaction the half-life is . The time required for of the reactant to be consumed is
Q12. A reaction products follows second-order kinetics: . If and after the concentration is , the half-life of the reaction is approximately
Q13. The initial rates for the reaction between A and B were measured as follows: Exp I: ; Exp II: ; Exp III: . The rate law and rate constant (with units) that best fit these data are
Q14. For consecutive first-order reactions with and initial concentration , the time at which the concentration of intermediate is maximum equals
Q15. Consider the mechanism: (1) (fast reversible), (2) (slow). Using the steady-state approximation for intermediate , the rate of formation of is