IB Chemistry HL: Chemical Kinetics and Reaction Mechanisms

1. Distinguish between the terms rate constant, overall order of reaction and order of reaction with respect to a particular reactant.

2. Deduce the rate expression for a reaction from experimental data.

The rate equation only depends on the final products formed in a reaction, not the concentrations of the reactants.

The rate expression for a reaction can be accurately predicted based solely on theoretical considerations without the need for experimentation.

The orders in a rate equation are determined based on the physical state of the reactants rather than their concentrations.

Experimental data is crucial in determining the rate expression for a reaction as theoretical predictions alone are not sufficient. The rate equation specifically relates the reaction speed to the concentrations of reactants, allowing for insights into the reaction mechanism.

Explanation

Experimental data is crucial in determining the rate expression for a reaction as theoretical predictions alone are not sufficient. The rate equation specifically relates the reaction speed to the concentrations of reactants, allowing for insights into the reaction mechanism.

3. Explain the concept that reactions can occur by more than one step and that the slowest step determines the rate of reaction (rate-determining step).

Catalyst: A substance that increases the rate of a reaction without being consumed.

Equilibrium constant: The ratio of products to reactants at equilibrium.

Activation energy: The energy needed for a reaction to occur.

4. Describe the relationship between reaction mechanism, order of reaction and rate-determining step.

The rate-determining step is always the first step in a multi-step reaction.

Mechanism is only relevant for single-step reactions and does not affect the overall reaction rate.

Order of reaction is determined solely by the concentration of reactants and does not relate to the reaction mechanism.

The correct answer highlights the importance of considering the entire mechanism in determining the rate-determining step and overall reaction rate, rather than being limited to specific scenarios. The incorrect answers provide common misconceptions that are contradicted by the relationship between reaction mechanism, order of reaction, and rate-determining step.

Explanation

The correct answer highlights the importance of considering the entire mechanism in determining the rate-determining step and overall reaction rate, rather than being limited to specific scenarios. The incorrect answers provide common misconceptions that are contradicted by the relationship between reaction mechanism, order of reaction, and rate-determining step.

5. Determine activation energy (Ea) values from the Arrhenius equation by a graphical method.

Conducting experiments at different temperatures to directly measure the activation energy.

Applying the principles of quantum mechanics to calculate the activation energy.

Using trial and error methods to guess the activation energy value.

The correct method to determine activation energy (Ea) values from the Arrhenius equation is by utilizing the provided equation and its logarithmic form. This method does not involve conducting experiments at different temperatures or applying quantum mechanics principles. Guessing or using trial and error methods is not a reliable approach for determining activation energy.

Explanation

The correct method to determine activation energy (Ea) values from the Arrhenius equation is by utilizing the provided equation and its logarithmic form. This method does not involve conducting experiments at different temperatures or applying quantum mechanics principles. Guessing or using trial and error methods is not a reliable approach for determining activation energy.