3.1 Rates of Reaction Flashcards
3.1a- Collision Theory
Relationships between rate & time?
t= 1/r
r= 1/t
3.1a- Collision Theory
Average rate calculation
Change in conc or vol
/
Change in time
3.1a- Collision Theory
Explain in, terms of Collision Theory, how decreasing particle size increases rate of reaction.
The surface area increases, so more particles are avaliable for collision, so rate of reaction increases.
3.1a- Collision Theory
Explain, in terms of Collision Theory, how increasing concentration increases rate of reaction.
The higher the concentration, the more particles in a given space, the more chance there is of successful collisions.
3.1a– Collision Theory
What type of graph shows the effect of temperature on rate of reaction?
Exponential
3.1a- Collision Theory
What type of graph shows the effect of temperature on rate of reaction?
Diagonal
/
3.1a- Collision Theory
What must happen for successful collisions?
Particles must have
* Kinetic energy greater than or equal to the Activation Energy (Ea)
* Correct collision geometry
3.1a- Collision Theory
Define “Activation Energy”
- The minimum amount of Kinetic energy required for a reaction to form an activated complex/ for a successful reaction to occur.
- Reactants to the top of the Hill
3.1a- Collision Geometry
Define “Correct Collision Geometry”
When particles collide side on
3.1b- Temperature & Kinetic Energy
Define “Temperature”
Can be regarded as a measure of the average kinetic energy of particles in a substance.
3.1b- Temperature & Kinetic Energy
Effect of temperature on reaction rate.
As temperature increases, there are more particles with kinetic energy greater than or equal to the activation energy. Therefore there will be more successful collisions & faster rate.
3.1c- Catalysts
Effect of Catalyst on rate
Catalysts speed up rate by decreasing the Activation Energy, providing an alternative pathway for reaction to occur.
3.1c- Catalysts
Define:
* Homogenous
* Heterogenous
- Reactant & Catalyst in same state
- Reactions & Catalyst in different states
3.1c- Catalysts
What are the 3 stages of a catalysed reaction?
- Adsorption
- Reaction
- Desorption
3.1d- Reaction Profiles
Enthalpy
- Symbol: ΔH
- Difference in energy between reactants & products
- ΔH = H(products)- H(reactants)
- Can have + or - values
3.1d- Reaction Profiles
What is an “Unstable Activated Complex”?
A Highly energetic & unstable complex formed between reactants
3.1d
Exothermic Reactions
- ΔH always -
- H(reactants) > H(products)
3.1d- Reaction Profiles
Endothermic Reactions
- ΔH always +
- H(reactants) < H(products)
3.1d- Reaction Profiles
Effect of a Catalyst on ΔH
No effect
