Kinetics Flashcards
Collision Theory
Reactions can only occur when collisions take place between particles with sufficient energy and orientation.
Activation Energy
Minimum energy required when particles collide to start a reaction. The energy needed to break the bonds in the reactants
Maxwell-Bolzmann Distribution
Shows the spread of energies that molecules have at a particular temperature
How can a reaction go to completion if few particles have energy greater than Ea?
Particles can gain energy through collisions
Increasing temperature on M-B distribution
Distribution shifts to the right. The curve becomes lower so the total area under the curve (total number of particles remains constant)
Decreasing temperature on M-B distribution
Distribution shifts to the left. The curve becomes higher so the total area under the curve (total number of particles remains constant)
Rate of reaction
Change in concentration of a reactant or product in a unit time
How to identify rate of reaction on a concentration-time graph
Gradient of the graph - mark a tangent to the graph extending the line to form the largest possible triangle to give the smallest error
Effect of increasing concentration and pressure
Rate of reaction increases as there are more particles per unit volume so particles collide with greater frequency.
Effect of doubling concentration
Double the number of particles per unit volume so double the frequency of effective collisions
Effect of increased concentration or pressure on a M-B distribution curve
Curve has same shape but is higher because there are more particles per unit volume. More molecules have E>Ea
Things to consider when drawing one rate curve compared to another.
Think about end point - will more or less particles be present than the original curve.
Think about initial rate - will the graph be steeper or shallower than the original
Effect of increasing temperature on RoR
Particles have increase kinetic energy so collisions are more frequent. Particles also are more likely to have E>Ea so collisions are more likely to be successful
Effect of increasing surface area on RoR
Increases RoR as a greater surface area will mean more frequent collisions between reactants
Definition of catalyst
Substance that increases the rate of reaction without being used up
