Topic 6/16: Kinetics Flashcards
Describe the collision theory.
- The particles must collide
- The particles must collide with appropriate geometry or orientation.
- The particles must collide with sufficient energy to bring about the reaction.
How does surface area affect rate?
The smaller the surface area, the fewer collisions will occur per unit time, decreasing rate.
How does temperature affect rate?
As temperature increases, the particles have greater kinetic energy. As more of the colliding particles posses energy greater than or equal to the activation energy, there will be more successful collisions per unit time, increasing rate.
How does concentration affect rate?
Increasing the concentration causes more particles per unit volume, which increases the frequency of successful collisions per unit time, increasing rate.
How does pressure affect rate?
Higher pressure compresses gas, increasing the concentration, which increases the successful collisions per unit time, increasing rate.
Describe how a catalyst works.
A catalyst provides an alternative pathway with a lower activation energy.
Define the term “order of reaction”.
The power of a reactant’s concentration in the rate equation.
Define the term “rate of reaction”.
The change in reactant concentration with time.
Describe the rate of reaction (gradient) at the start of the curve.
The rate of reaction is the fastest (gradient is the steepest) because there is a high concentration of reactant particles, thus a high frequency of successful collisions.
Define activation energy.
The minimum amount of energy required for colliding particles to react.
How is the rate constant (k) changed?
The rate constant is changed by temperature.
Define half-life of a reaction.
Time for the reactant concentration to halve
What is the equation for the half-life of a reaction?
t1/2 = 0.693/k
Why are single step mechanisms unlikely for certain reactions?
The reaction involves three or more molecules, which is geometrically unlikely.
