Activation Energy and Temperature Effects

This page focuses on the concept of activation energy and how temperature and catalysts affect reaction rates.

Activation Energy (Ea) is the minimum energy required for reactants to form products in a chemical reaction.

Highlight: Only molecules with energy equal to or greater than the activation energy can participate in successful collisions.

The relationship between temperature and reaction rate is explained:

1. Temperature increases the average kinetic energy of molecules.
2. More molecules gain energy above the activation energy threshold.
3. This results in more successful collisions and faster reaction rates.

Example: A graph illustrates how a small increase in temperature (from T1 to T2) significantly increases the number of molecules with sufficient energy to react.

Catalysts work by lowering the activation energy required for successful collisions. This allows more molecules to have the necessary energy, increasing the number of successful collisions and speeding up the reaction.

Example: Some industrial catalysts include:

• Iron in the Haber process for ammonia production
• Platinum in nitric acid manufacture (Ostwald process)
• Rhodium and Platinum in catalytic converters

The page emphasizes that reactions with low activation energy tend to be fast, while those with high activation energy are typically slower.

Rates of Reaction and Collision Theory

This page introduces the concept of reaction rates and collision theory in chemistry. It explains how chemical reactions occur at the molecular level and what factors influence their speed.

Collision theory states that for a chemical reaction to occur, reactant molecules must collide with enough energy and in the correct orientation. These are called successful collisions.

Definition: The minimum kinetic energy required for a reaction to occur is called the activation energy (EA).

Factors affecting reaction rates include:

• Temperature
• Concentration
• Pressure
• Particle size (surface area)
• Use of catalysts

Highlight: The rate of a reaction increases with more successful collisions between reactant molecules.

The page illustrates collision geometry using the reaction between hydrogen and bromine as an example. It shows how molecules must collide in the right orientation to form an activated complex and eventually product molecules.

Vocabulary: An activated complex is an unstable, high-energy arrangement of atoms formed during a collision between reactant molecules.