3.1.9.3 Rate-Determining Step

• Order the steps of a reaction mechanism based on their contribution to the overall reaction rate:

  1️⃣ Rate-determining step (Slow, Significant contribution)

  2️⃣ Step 2 (Fast, Minimal contribution)

  3️⃣ Step 3 (Fast, Minimal contribution)
• What role does the rate-determining step play in reaction mechanisms?

  Limits the overall reaction rate
• The rate-determining step is crucial for understanding and controlling reaction speeds
• To identify the rate-determining step in a multi-step mechanism, analyze the relative rates
• The rate equation for the reaction C + D → E is rate = k[C][D]
• Match the process with its rate-determining step:

  Catalytic converter in cars ↔️ Adsorption of reactants

  Haber process for ammonia synthesis ↔️ Dissociation of N₂
• Steps to calculate rate constants and reaction orders:

  1️⃣ Identify the rate equation

  2️⃣ Determine reaction orders

  3️⃣ Calculate the rate constant
• What is the first step in calculating rate constants and reaction orders?

  Determine reaction orders
• The rate constant for a first-order reaction is calculated as k = rate / [A].


  True
• The first step in calculating rate constants and reaction orders is to identify the rate equation
• What determines the reaction order in a rate equation?

  Experimental data
• The rate-determining step limits the overall rate of the reaction.

  True
• Steps to identify the rate-determining step in a multi-step mechanism

  1️⃣ Analyze the relative rates of each step

  2️⃣ Determine which step is the slowest

  3️⃣ Identify the slowest step as the rate-determining step
• If the rate equation includes intermediates, they must be expressed in terms of reactants
• What is the rate-determining step in the Haber process for ammonia synthesis?

  Dissociation of nitrogen
• What is the primary purpose of the catalytic converter in cars?

  Remove harmful pollutants
• For the reaction 2A → B, if the rate quadruples when [A] doubles, the reaction is second-order with respect to A.
• The rate-determining step limits the overall rate of the reaction because it is the slowest step.


  True
• The rate-determining step is the slowest step in a reaction mechanism
• Chemists use the rate-determining step to design catalysts and optimize reaction conditions
• The rate-determining step (Step 1) controls the pace of the entire reaction.


  True
• What must be included in the final rate equation?

  Rate constant and reactant concentrations
• The final rate equation for the reaction mechanism is rate = kK[A][B][D]
• What is the rate-determining step in a chemical reaction?

  The slowest step
• What is the first step in calculating rate constants and reaction orders?

  Identify the rate equation
• What is the rate equation for the reaction 2A → B if the rate quadruples when [A] doubles?

  rate = k[A]^2
• What is molecularity in the context of a rate-determining step?

  Number of reactant molecules
• According to collision theory, what three factors influence the rate-determining step?

  Frequency, energy, orientation
• What does a higher collision frequency in the rate-determining step lead to?

  More potential collisions
• The rate-determining step is the fastest step in a reaction mechanism.

  False
• The rate-determining step helps chemists design catalysts and optimize reaction conditions
• Even if other steps in a mechanism are fast, the overall reaction rate is limited by the rate-determining step.


  True
• A rate-determining step with a slow reaction rate has a significant contribution to the overall reaction rate.


  True
• Match the step with its contribution to the overall reaction rate:

  Rate-Determining Step ↔️ Significant

  Fast Step ↔️ Minimal
• Steps to derive a rate equation using the rate-determining step:

  1️⃣ Identify the rate-determining step

  2️⃣ Write the rate equation for this step

  3️⃣ Use stoichiometry to determine reaction orders

  4️⃣ Include rate constant and concentrations
• The overall rate equation for the reaction A + B ⇌ C followed by C + D → E is rate = kK[A][B][D]
• The rate-determining step in the Haber process is the dissociation of the nitrogen molecule
• If the rate doubles when the concentration of A doubles, the reaction A → B is first-order
• What happens to the reaction rate when the concentration of A is doubled in a first-order reaction (A → B)?

  Rate doubles
• What is the rate equation for a reaction A → B where doubling [A] doubles the reaction rate?

  rate = k[A]