Online Lecture Series for PG Students
ACTIVATED COMPLEX THEORY
Dr. Sumit Kumar Assistant Professor
PG Department of Chemistry Magadh University, Bodh Gaya
You can contact me at [email protected]
TERMINOLOGY • Rate of reaction- The rate of a reaction is the speed at which a chemical reaction
happens. how fast, how many moles are produced or consumed in a unit of time.
• Collision Theory- Theory used to predict the rates of chemical reactions,
particularly for gases. The collision theory is based on the assumption that for
a reaction to occur it is necessary for the reacting species (atoms or molecules)
to come together or collide with one another.
• Activation Energy- The minimum amount of energy that is required to activate
atoms or molecules to a condition in which they can undergo chemical
transformation or physical transport.
• Activated Complex- An intermediate or transitional structure formed during the
course of reaction
COLLISION THEORY Collision theory, theory used to predict the rates of chemical reactions, particularly for gases. The collision theory is based on the assumption that for a reaction to occur it is necessary for the reacting species (atoms or molecules) to come together or collide with one another. Not all collisions, however, bring about chemical change. A collision will be effective in producing chemical change only if the species brought together possess a certain minimum value of internal energy, equal to the activation energy of the reaction.
ACTIVATION ENERGY
• Particles need enough energy to overcome the activation energy, the smallest amount of energy needed to start a reaction.
• ALL REACTIONS need to absorb energy to overcome the activation energy. However, exothermic reactions release more energy than initially absorbed.
• When the particles have absorbed enough energy they form an activated complex (intermediate state between reactants and products).
ACTIVATION ENERGY
FACTORS THAT AFFECT RATE OF REACTION
1. Concentration More concentration more collisions For gases increase in pressure increases concentration increases rate of reaction
2. Temperature increase in temperature more K. E. (particles move faster)
more collisions
3. Surface Area
increases surface area more exposed particles more collisions
4. Nature of Reactants
Ionic substances react faster than molecules; involve less rearrangement during a reaction.
5. Catalysts
Lowers activation energy; particles need less energy to react
FACTORS THAT AFFECT RATE OF REACTION
*Catalyst does not affect ΔH; there is no difference in ΔH.*
SUMMARY
Rate of reaction
Increases
Ionic compounds More Concentration Increases
More pressure (gas) High
Temperature Increases
Surface Area More
Catalyst Increases
