Kinetics Flashcards
What does the collision theory state?
For a chemical reaction to take place the particles need to collide with each other in the correct orientation and with enough energy
What is an ineffective collision?
When particles collide in wrong orientation or don’t have enough energy so bounce off each other without a chemical reaction
What is collision frequency?
The number of collisions per unit time
What does a higher collision frequency result in?
Increased number of particles with activation energy
Increase in rate of reaction
What is meant by activation energy?
The minimum amount of energy reactant particles need to overcome for a reaction to take place
What is a catalyst?
A substance that increases the rate of reaction without taking part in the chemical reaction
How do catalysts work?
Provide particles with an alternative mechanism with lower activation energy
What is meant by rate of reaction?
The speed at which a chemical reaction takes place
What units are used to represent rate of reaction?
mol dm⁻³ s⁻¹ or mol dm⁻³ min⁻¹
How is rate of reaction calculated at the start of a reaction?
rate of reaction = change in amount of reactants or products / time
What happens to concentrations of reactants and products as a reaction proceeds?
The concentration of reactants decreases
The concentration of products increases
Is rate of reaction constant?
No it changes throughout the reaction
What is used to calculate rate of reaction during the reaction?
A concentration-time graph
What should be kept constant when measurements for rate of reaction are being taken?
Temperature
How can rate of reaction be calculated as the reaction proceeds?
By taking short time intervals
Drawing tangeants
What is a Maxwell-Boltzmann distribution curve?
A graph that shows the distribution of energies at a certain temperature
What can we find out from a Maxwell-Boltzmann distribution curve?
The proportion of molecules in sample that have achieved activation energy
What effect does temperature have on rate of reaction?
Particles gain more kinetic energy
So more frequent collisions
High proportion of particles possess activation energy
Proportion of successful collisions increases
Rate of reaction higher
What effect does increasing temperature have on the Boltzmann distribution curve?
Curve flattens and the peak shifts right
What effect does concentration have on rate of reaction?
More concentrated solution, greater number of particles in given volume
Increased collision frequency
Increased rate of reaction
What effect does pressure have on rate of reaction?
Increased pressure means molecules have less space to move
Increased collision frequency
Increased rate of reaction
What is catalysis?
The process in which the rate of a chemical reaction is increased by adding a catalyst
How do catalysts increase rate of reaction?
Provide reactants an alternative reaction pathway with lower activation energy
What are the two types of catalysts?
Homogeneous catalysts
Heterogeneous catalysts
