Topic 9 - Kinetics I Flashcards
What are the two definitions of rate of reaction?
- How quickly the reactants are used up/ how quickly the products are formed
- The change of concentration of a reactant/product per unit time
What are the units for rate of a reaction?
moldm^-3s^-1
What type of graph can you plot to find the rate of reaction?
A concentration-time graph
What are the 5 factors that affect the rate of reaction?
- Temperature
- Surface Area of reactant
- Concentration
- Catalyst
- Pressure
What are the three assumptions of collision theory?
- The particles have to collide
- Particles must have at least the activation energy
- Particles must collide in the correct orientation
What are the 2 different ways that changes in rate of reaction due to changing conditions can be explained?
- Simple collision theory
- Boltzmann distribution curve
How would you explain the change in rate using simple collision theory when the concentration of a reactant is changed?
- More particles in a given volume
- More frequent collisions
- Higher rate of reaction
How would you explain the change in rate using simple collision theory when the surface area of a reactant is changed?
- Particles have more kinetic energy
- Therefore, particles move faster so collide more frequently AND more particles have an energy that is greater than the activation energy of the reaction
- A greater proportion of collision are successful
- Higher rate of reaction
How would you explain the change in rate using simple collision theory when the temperature is changed?
- More available particles to collide with
- Increased frequency of collisions
- Higher rate of reaction
What does the area under the line of a Boltzmann Distribution curve show us?
The total number of particles
How would you explain the change in rate using Boltmann’s distribution when the temperature is changed?
- The curve is shifted to the right with the peak lower but the bottom of the curve plateauing higher -> the area under the graph remains constant
- Larger area under the graph that is to the right of the activation energy line
- An increase kinetic energy of the particles
- Area under the curve above the activation energy is larger at higher temperatures so a greater proportion of particles have E >= Ea
- Increased proportion of successful collisions
- Particles are also moving faster so there si an increased frequency of collisions
How would you explain the change in rate using Boltmann’s distribution when a catalyst is added?
- Catalyst provides an alternate pathway with a lower activation energy for a reaction to proceed via
- Increased area to the right of the activation energy line meaning that a greater proportion of particles have the required activation energy
- Increased proportion of successful collisions
How do you find the rate of reaction at different points on a concentration - time graph?
Take the gradient at that point
What are the two types of catalyst?
Heterogenous and Homogenous
What is the definition of a heterogenous catalyst?
The reactants and catalyst are in a different physical state
