Tutorial 1 — Chemical Kinetics

Note: This tutorial PDF consists primarily of scanned images. The questions below are reconstructed based on typical FAD1018 Tutorial 1 content on Chemical Kinetics.

Learning Outcomes

  1. Understand reaction rates and rate laws
  2. Determine rate constants and reaction orders
  3. Apply integrated rate laws
  4. Understand collision theory and activation energy
  5. Use Arrhenius equation

Part A: Rate Laws and Reaction Order

Question 1

For the reaction: $2A + B \rightarrow C$, the following data were obtained:

Experiment [A] (M) [B] (M) Initial Rate (M/s)
1 0.10 0.10 $2.0 \times 10^{-3}$
2 0.20 0.10 $8.0 \times 10^{-3}$
3 0.20 0.20 $1.6 \times 10^{-2}$

a) Determine the rate law for the reaction.

b) Calculate the rate constant $k$.

c) What is the overall order of the reaction?

Question 2

The decomposition of N₂O₅ follows first-order kinetics:

$$2N_2O_5(g) \rightarrow 4NO_2(g) + O_2(g)$$

a) Write the rate law expression.

b) If the rate constant is $3.4 \times 10^{-5}$ s⁻¹ at 25°C, calculate:

  • The half-life of N₂O₅
  • The time required for the concentration to drop from 0.050 M to 0.010 M

Part B: Integrated Rate Laws

Question 3

A second-order reaction: $2NO_2(g) \rightarrow 2NO(g) + O_2(g)$ has a rate constant of $0.54$ M⁻¹s⁻¹ at 300°C.

a) Starting with $[NO_2]_0 = 0.010$ M, how long will it take for the concentration to decrease to $0.0050$ M?

b) Calculate the half-life when $[NO_2]_0 = 0.010$ M.

Part C: Arrhenius Equation

Question 4

The rate constant for a reaction doubles when the temperature is increased from 25°C to 35°C.

a) Calculate the activation energy $E_a$.

b) What is the value of the pre-exponential factor $A$?

Part D: Reaction Mechanisms

Question 5

Consider the following proposed mechanism:

Step 1: $NO_2 + NO_2 \rightarrow NO_3 + NO$ (slow) Step 2: $NO_3 + CO \rightarrow NO_2 + CO_2$ (fast)

a) Identify the intermediate.

b) Determine the rate law predicted by this mechanism.

c) Does the mechanism agree with the overall reaction: $NO_2 + CO \rightarrow NO + CO_2$?

Key Concepts

  • Rate Law — Mathematical expression relating reaction rate to concentrations
  • Order of Reaction — Exponent in the rate law
  • Half-life — Time for concentration to reduce by half
  • Activation Energy — Energy barrier for reaction
  • Arrhenius Equation — Temperature dependence of rate constants

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