Rate Equation and Reaction Mechanism

Multiple Choice

Which of the following is a key objective when studying rate expressions and reaction mechanisms?

• To deduce the rate expression from experimental data

• To memorize all chemical equations

• To ignore graphical representations of reactions

• To focus only on stoichiometric data without kinetics

Open Ended

Why is understanding reaction kinetics important in the study of chemistry?

Open Ended

Explain why the rate constant 'k' must always be reported with the temperature at which it was measured.

Multiple Choice

Based on the data from the experiments, which reactant(s) affect the rate of reaction and what is the overall order of the reaction?

• Only A, first order overall

• Only C, second order overall

• A and C, third order overall

• A, B, and C, third order overall

Fill in the Blank

Fill in the blank: The rate constant for the reaction calculated using the data from experiment 1 is ___ mol⁻² dm⁶ s⁻¹.

Open Ended

How can the units for the rate constant be determined for a reaction of any overall order?

Multiple Select

Select all the correct units for the rate constant for the following overall orders of reaction.

• Zero order: mol dm⁻³ s⁻¹

• First order: s⁻¹

• Second order: mol⁻¹ dm³ s⁻¹

• Third order: mol⁻² dm⁶ s⁻¹

Multiple Choice

Which two types of graphs can be used to determine the order of a reaction?

• Concentration against time and initial rate against concentration

• Concentration against temperature and initial rate against pressure

• Initial rate against temperature and concentration against pressure

• Concentration against volume and initial rate against volume

Open Ended

Explain how you would identify a zero order reaction using a concentration vs. time graph.

Multiple Select

Which of the following statements about the initial rate against concentration graph is/are correct?

• A zero order reaction produces a horizontal line.

• A first order reaction produces a straight line with a positive slope.

• A second order reaction produces a parabola.

• A zero order reaction produces a straight line with a positive slope.

Fill in the Blank

The time required for the concentration to fall from its initial value to half its initial value is called the ___ of the reaction.

Multiple Choice

Which of the following best describes a pseudo first-order reaction?

• A reaction where the rate depends on the concentration of two reactants equally.

• A reaction where the rate law appears to be first order because one reactant is in large excess.

• A reaction where the rate is independent of reactant concentrations.

• A reaction that only occurs at high temperatures.

Open Ended

Explain why the rate of the overall reaction is determined by the slowest step in the reaction mechanism.

Multiple Select

Which of the following statements about unimolecular and bimolecular processes are correct?

• Unimolecular processes involve two species colliding.

• Bimolecular processes are always first order overall.

• Unimolecular processes are first order with respect to the reactant.

• Bimolecular processes involve the interaction of two species.

Fill in the Blank

The rate law for a unimolecular step is proportional to ___

Multiple Choice

Which of the following is true about intermediates in a reaction mechanism?

• They occur at a potential energy maximum.

• They exist only for a transient moment and cannot be isolated.

• They are formed in one step and consumed in a subsequent step.

• They exist part way through every step of a reaction.

Open Ended

Compare and contrast transition states and intermediates in a chemical reaction mechanism. Provide at least two differences.

Open Ended

Explain why the rate of the iodination of propanone is independent of the concentration of iodine, even though iodine is a reactant in the overall equation.

Multiple Choice

Which of the following best describes the experimentally determined rate law for the iodination of propanone in acidic solution?

• Rate = k [CH3COCH3][I2]

• Rate = k [CH3COCH3][H+]

• Rate = k [CH3COCH3][I2][H+]

• Rate = k [I2][H+]

Multiple Choice

Which steps in the commonly accepted mechanism for the iodination of propanone are considered fast?

• The first and second steps

• The first and third steps

• The second and third steps

• All steps are slow

Fill in the Blank

The rate determining step in the iodination of propanone involves the formation of ___ as an intermediate.

Multiple Choice

Which of the following is NOT a learning objective for the topic 'Rate Expression and Reaction Mechanism'?

• Deduce the rate expression from experimental data.

• Sketch and analyze graphical representations for different order reactions.

• Evaluate proposed reaction mechanisms for consistency with data.

• Memorize all chemical elements and their symbols.

Open Ended

Reflecting on today's lesson about rate expressions and reaction mechanisms, what is one concept you found most interesting or would like to learn more about?