Chemistry Reaction Rates, Mechanisms, and Catalysis: Key Concepts and Formulas

What is the rate of a chemical reaction?

The rate of a chemical reaction is a measure of how fast a reaction occurs, reflecting the change in the concentration of a reactant or product per unit time, usually reported in units of M/s.

What does the rate law describe?

The rate law shows the relationship between the rate of a reaction and the concentrations of each reactant, and must be determined experimentally.

How does the reaction order affect the rate of a reaction?

The rate of a first-order reaction is directly proportional to the concentration of the reactant, while for a second-order reaction, it is proportional to the square of the concentration, and for a zero-order reaction, it is independent of the concentration.

What is the integrated rate law for a zero-order reaction?

The integrated rate law for a zero-order reaction shows that the concentration of the reactant varies linearly with time.

How is the half-life of a reaction defined?

The half-life of a reaction is the time required for the concentration of a reactant to fall to one-half of its initial value.

What is the Arrhenius equation?

The Arrhenius equation expresses the rate constant of a reaction as a function of temperature, incorporating a frequency factor and an exponential factor.

What is activation energy (E₂)?

Activation energy is the barrier that reactants must overcome to become products.

What is the frequency factor (A) in the Arrhenius equation?

The frequency factor represents the number of times that the reactants approach the activation barrier per unit time.

What is the role of the activated complex in a reaction?

The activated complex, or transition state, is a temporary state during a reaction where reactants are transformed into products.

What is a reaction mechanism?

A reaction mechanism is the series of individual steps by which a chemical reaction occurs.

What is molecularity in a reaction?

Molecularity refers to the number of reactant molecules involved in an elementary step of a reaction.

What is a catalyst?

A catalyst is a substance that increases the rate of a chemical reaction by providing an alternative mechanism with a lower activation energy.

What is the difference between homogeneous and heterogeneous catalysis?

Homogeneous catalysis occurs in the same phase as the reactants, while heterogeneous catalysis occurs in a different phase.

What is an enzyme?

An enzyme is a biological catalyst that increases the rate of specific biochemical reactions.

What is the rate-determining step in a reaction mechanism?

The rate-determining step is the slowest step in a reaction mechanism that controls the overall reaction rate.

What is the collision model in chemistry?

The collision model states that reactions occur as a result of sufficiently energetic collisions between molecules.

What is the orientation factor in the context of reactions?

The orientation factor is the fraction of collisions that have the proper orientation for a reaction to occur.

What does the term 'reaction intermediate' refer to?

A reaction intermediate is a species that is formed during the reaction but is not present in the final products.

How does temperature affect reaction rates?

Generally, increasing temperature increases the rate constant and the rate of reaction due to more energetic collisions.

What is bimolecular reaction?

A bimolecular reaction involves two reactant molecules in an elementary step.

What is termolecular reaction?

A termolecular reaction involves three reactant molecules in an elementary step.

What is the significance of an Arrhenius plot?

An Arrhenius plot is used to determine the frequency factor and activation energy by plotting the natural logarithm of the rate constant against the inverse of temperature.

What is the difference between average rate and instantaneous rate of reaction?

The average rate is calculated over a time interval, while the instantaneous rate is the rate at a specific moment in time.

What is the effect of doubling the concentration of a reactant in a zero-order reaction?

In a zero-order reaction, doubling the concentration of the reactant does not affect the rate of reaction.

What is the effect of doubling the concentration of a reactant in a first-order reaction?

In a first-order reaction, doubling the concentration of the reactant doubles the rate of reaction.

What is the effect of doubling the concentration of a reactant in a second-order reaction?

In a second-order reaction, doubling the concentration of the reactant quadruples the rate of reaction.