Kinetics

Rucete ✏ Chemistry In a Nutshell

1. Collision Theory

• Chemical reactions occur when reactant particles collide with enough energy and proper orientation.

• Effective collisions lead to product formation.

• Activation energy (Ea): the minimum energy required for a successful collision.

• Only a fraction of collisions are successful because not all particles have sufficient energy.

2. Factors That Affect Reaction Rate

• Concentration: Higher concentration = more collisions = faster reaction.

• Temperature: Higher temperature = particles move faster = more collisions with enough energy.

• Surface Area: Increased surface area (especially in solids) = more area for collisions = faster reaction.

• Catalyst: Lowers activation energy → increases the number of successful collisions.

3. Activation Energy (Ea)

• Represented in kJ/mol.

• Reactions with lower Ea proceed faster.

• At higher temperatures, more molecules have energy ≥ Ea, so the reaction is faster.

4. Arrhenius Equation

$$k=A{e}^{\frac{-E_a}{RT}}$$

• $k$: rate constant

• $A$: frequency factor (related to how often molecules collide)

• $E_a$: activation energy

• $R$: gas constant (8.314 J/mol·K)

• $T$: temperature in Kelvin

5. Reaction Mechanism

• The sequence of steps that make up a reaction.

• Each step is called an elementary reaction.

• The slowest step is the rate-determining step (controls the overall reaction rate).

In a nutshell

More Collisions, More Speed

• High temp, high concentration, big surface area, or catalyst = faster reaction.

• Only effective collisions with enough energy (Ea) lead to products.