Kinetics Flashcards
(17 cards)
What is the collision theory?
A theory that describes how chemical reactions occur through molecular collisions and why reaction rates vary between reactions
What can the rate of reaction be increased by?
-increasing the frequency of collisions
-increasing the energyof reactants
-lowering the activation energy
What are the four ways that rate of reaction can be increased?
-increasing concentration
-increasing surface area
-increasing temperature
-adding a catalyst
What is the definition of activation energy?
The minimum amount of energy needed for an reaction to occur
Explain why most collisions do not lead to a reaction
The molecules may not have enough kinetic energy or orientation of the molecules when they collide may prevent the reaction from occurring.
What is enthalpy change?
A heat change at constant pressure
What is rate of reaction?
Change in the concentration of a reactant (or product) per unit time
What is an exothermic reaction?
Where the reactants are higher in energy than the products
What is an endothermic reaction?
The reactants are lower in energy than the products
What is collision frequency?
The number of collisions per unit time
What is successful (effective) collision?
Occurs when particles collide with sufficient energy to result in a reaction
What is the difference between exothermic reactions and endothermic reactions?
In exothermic reactions.
The enthalpy of the reacting system decreases
The enthalpy change is negative
Energy is transferred from the reacting system to the surroundings
In endothermic reactions.
The enthalpy of the reacting system increases
The enthalpy change is positive
Energy is transferred to the reacting system from the surroundings
How does increasing temperature, increase the rate of reaction?
-Increasing temperature increases kinetic energy of particles.
-This increases the frequency of collisions and a greater proportion of collisions will have the energy required to react.
-This gives more successful collisions
Curve shifts down and to the right.
How does increasing the concentration of a solution in read the rate of reaction?
-increasing the concentration increases the number of reactant molecules per unit volume.
-this increased the frequency of collisions -This gives more successful collisions
The maxwell-Boltzmann curve shifts up, area increases due to increase in particles. By putting more particles in the same unit volume we increase frequency of collisions. Number of particles with sufficient energy increases, increase number of successful collisions
How does increasing the pressure of a gas increase the rate of reaction?
-increasing pressure forces particles together.
This increases the frequency of collisions
-this gives more successful collisions
How does increasing the surface area of a solid increase the rate of reaction?
-increasing the surface area means that more reactants are exposed
-increases the frequency of collisions
-this gives more successful collisions
How does using a catalyst increase the rate of reaction?
-Using a catalyst increases the rate of reaction by providing an alternative pathway with a lower activation energy
-more molecules have sufficient energy to react
