Topic 9- Kinetics Flashcards
A reaction won’t take place between two particles unless…
They collide in the right direction- facing each other correctly.
With at least the kinetic energy of the activation energy
What is on the X and Y axis on the Maxwell Boltzman graphs
X= kinetic energy
Y=Number of molecules.
What happens to particles when you increase the temperature?
They will have more kinetic energy and will move faster. Therefore more particles can react as they have at least the activation energy.
What happens to the Maxwell Boltzman curve when you increase the temperature?
The curve is shifted to the right, and more molecules have at least the activation energy.
Name 3 things other than temperature that affect the rate of reaction
Pressure- more particles in given volume so collide more freq
Concentration- more particles in volume so more freq collisions
Catalysts- lower activation energy so more particles with enough energy to react.
How to work out rate of reaction?
change in y / change in x
or with data: amount of product formed / time taken
What does a catalyst do?
Increases rate of reaction by providing an alternative reaction pathway with a lower activation energy so a greater proportion of collision result in reaction.
Catalyst chemically UNCHANGED
What does a catalyst do to the Maxwell Boltzman graph?
The activation energy shifts further to the left, increasing the area therefore more molecules have enough energy to react when they collide
Name a catalyst used in ammonia production?
Iron catalyst.
How does a catalyst provide economic benefits?
Prevents expensive use of high temperatures (lower production cost)
And it increases the amount of product made in shorter time
Makes more useful products e.g higher melting point
How can using a catalyst make the properties of a product more useful?
polyethene w/o catalyst = less dense, less rigid.
WITH a catalyst= more dense, more rigid, higher melting point.
What is a heterogeneous catalyst?
Catalyst in a different phase from reactants i.e. different physical state e.g. solid.
This increases surface area so more molecules can react at the same time = increased rate.
Lowers activation energy.
Many catalysts will usually only work on a ……. …….
single reaction- specific to certain reactions
Describe the steps when using a solid heterogeneous catalyst e.g. iron in Haber Process
- Adsorption of reactant molecules onto surface of catalyst
- Weakening of reactant molecules’ bond therefore breaking reactants and forming radicals
- Desorption of the product from catalyst
Why does a reaction between a liquid and a solid have a greater rate than two solids (2)
- particles in liquid move freely and all able to collide with solid particles
- whereas particles in solids just vibrate about fixed positions, so only touching surfaces between solids react
