Rates Of Reaction Flashcards
How do we work out the rate of reaction? And what are the units?
Change in concentration/ time
moldm-3 s-1
What are the 5 factors affecting rate of reaction?
- Concentration
- Pressure
- Temperature
- Surface area
- Catalyst
How do each of these factors affect the rate?
- Increased Concentration- increase rate as more molecules so more frequent collisions
- Increased pressure- increased rate as more molecules for more frequent collisions
- Increased temp- increased rate as more energy so more frequent collisions
- Surface area increased- increased rate- more frequent collisions
- Catalyst- provided an alternative rate with a lower activation energy increasing the rate
What is a catalyst?
Increases the rate of reactions without being used up in the process by providing an alternative reaction path with a lower activation energy.
What is the difference between a heterogeneous and homogeneous catalyst?
Heterogeneous- one is a different phase to the reactants (eg state)
Homogeneous- one in the same phase to the reactants (eg state)
Describe the variation in speeds in a gas or liquid:
Some molecules move fast as have a high energy
Some move slow as have low energy
Most have an average energy
Draw a Boltzman distribution graph.
Increases then peaks decreases again and levels but does not touch the X axis
What are the properties to a Boltzman curve?
Area under curve= number of molecules
No molecules have no energy
No molecules have a maximum energy
Draw on the Ea onto the graph and what does this mean?
(Near the end)
Only molecules with energy greater than the Ea can react
Draw and Describe the line of a Boltzman distribution at a higher temperature:
Peak is lower and to the right
Area under the curve is the same
All molecules have more energy
Many more molecules have energy greater than the Ea so many more can react for a relatively small increase in temp
Draw on the Ea when a catalyst is used:
Ec is labelled before the previous Ea
What is the economic importance of catalysts?
Allow quick and easy production of chemicals requiring lower temps less energy so reduce waste
What catalyst is used for the haber process, what type is it and why?
Solid iron
Heterogeneous
Weakens the triple N-N bond
What are enzymes and what are the benefits of using them?
Homogenous biological catalysts Used as low temps and pressures Non toxic Biodegradable High yields of single product due to them being specific
What is chemical sustainability?
The most effective use of resources to ensure their availability in the future without damage to the environment.
