✅9 - Kinetics I Flashcards
What is collision theory?
Particles must collide to react
What are the criteria for particles to react?
They must collide in the right orientation
They must collide in with the minimum amount of kinetic energy
What is activation energy?
The minimum amount of kinetic energy needed to for the particles to react
What is a reaction profile diagram?
Shows the progress of the reaction over time, with the energy of the reactants and products
What happens when the temperature is increased?
Reactions progress faster
How does higher temperature change the Maxwell-Boltzman distribution?
It moves to the right
Why does increasing temperature speed up a reaction?
The molecules have more kinetic energy and so collide more often
Why does increasing concentration speed up a reaction?
If you increase the concentration of reactants in solution, there are more particles in a given volume of the solution, so they collide more frequently
Why does increasing pressure speed up a reaction?
If any of the reactants are gases, there are more molecules of the gas in the volume so there are more successful collisions
Why do catalysts speed up reactions?
They lower the activation every by providing a different way for bonds to be broken, and then more molecules have the required energy to react
What does rate of reaction tell you?
How fast reactants are converted to products
How can rate of reaction be worked out?
From the gradient of a graph
How would you calculate gradient?
Change in y / change in x
How would you work out the gradient of a curved graph?
By drawing a tangent
How can you work out the initial rate of reaction?
By calculating the gradient of the intial part of the graph
How can you work out rates of reaction from experimental data?
amount of reactant used or amount of product made/time taken
What is the rate of reaction proportional to?
1/time
Why does a catalyst increase the rate of reaction?
By providing an alternative pathway for the reaction
What is a benefit of using a catalyst?
They don;t get used u in reactions so only a small amount is needed
What is a disadvantage of using a catalyst?
They are very specific
What is a heterogeneous catalyst?
One in a different phase to the reactants
What do solid heterogeneous catalysts provide?
A surface for the reaction to take place on
How do heterogeneous catalysts work?
The reactant molecules are adsorped, then the bonds are weakened and the new molecules are formed. Then, they are desorped
What is a homogeneous catalyst?
One in the same physical state as the reactants
How do homogeneous catalysts work?
They combine with the reactants to make an intermediate species, then forming the products
What economic benefits do catalysts have?
They lower costs of production, make more products in a shorter time and make better products
What catalyst is used in ammonia production?
Iron
How does polyethene behave when made without a catalyst?
It is less dense and less rigid
How does polyethene behave when made with a catalyst
It is more dense, more rigid and has a higher melting point
What does the Maxwell-Boltzmann distribution show?
The proportion of particles with a certain amount of energy
