3.2.2 Reaction Rates Flashcards
(16 cards)
What is collision theory?
For a chemical reaction to occur
-the particles must collide with sufficient energy to overcome the activation energy
-the particles must collide with the correct orientation
What is the rate of reaction?
The change in concentration of a reactant or a product in a given time
What are the factors that affect rate of reaction?
1) Temperature
2) Pressure
3) Concentration
4) Surface area
5) adding a catalyst
What are the methods in measuring the rate of reaction?
1) Change in mass
2) Change in gas volume of products
3) Change in concentration of reactants or products
4) Change in concentration of reactants or products
On a graph, what is the rate of reaction equal to?
The gradient
What is a catalyst?
Increases the rate of reaction without being used up in the process. It provides an alternative route for the reaction to follow with a lower activation energy
Heterogenous catalyst
The catalyst is in a different phase from the reactants. Usually are solids
Homogenous Catalyst
Catalysts are in the same phase as reactants.
Benefits of catalyst
1) allows chemical reactions to take place at lower temperatures and pressures. So fewer fossil fuels need to be burned
2) reduced global warming
3) reduced energy demands and reduced costs
4) increases ROR even at lower temperatures, so helps increase the energy efficiency
What is the Maxwell Boltzmann Distribution?
Shows the spread of energies that a molecule of a gas or liquid have at a particular temperature
What are the key features of a Boltzmann distribution?
The area under the curve represents the total number of molecules in the sample
Another key feature of the Boltzmann distribution
No molecules have 0 energy. This is shown as the curve starts at the origin
Another feature of the Boltzmann distribution
There is no maximum energy for a molecule. This is shown where there is an asymptote
Another key feature of the Boltzmann distribution
Only a small proportion of molecules are able to react. Only molecules with an energy equal to or greater than the activation energy will be able to react
What is the effect of temperature on the Boltzmann distribution graph?
-At higher temperatures, the kinetic energy of all the molecules will increase
- the graph will be lower and will shift to the right
- the area above Ea will be greater
- the overall area under the curve will remain the same because the number of molecules in the sample doesn’t change
What is the effect of a catalyst on the Boltzmann distribution graph?
When a catalyst is added, there is no change in the number or distribution of energy within molecules. Therefore the shape and area under the graph remain the same. However more particles will have energy greater than the Ea.
