Reaction Rates Flashcards
A reaction won’t take place between two particles unless…
They collide in the right direction. They need to be facing each other the right way.
They collide with at least a certain minimum amount of kinetic energy.
What is the activation energy?
The minimum amount of kinetic energy particles need to react. The particles need this much energy to break the bonds to start the reaction.
What happens when you increase the temperature of a reaction?
The particles will on average have more energy and will move faster.
A greater proportion will therefore have more energy than the activation energy and be able to react.
Because the molecules are flying about faster, they’ll collide more often.
How does increasing concentration speed up reactions?
If you increase the concentration of reactants in a solution, the particles will be closer together on average.
If they’re closer, they’ll collide more often. If there are more collisions, they’ll have more chances to react.
How does increasing pressure speed up reactions?
If any reactants are gases, increasing pressure will increase the rate of reaction.
At higher pressures, the particles will be closer together, increasing the chance of successful collisions.
How does using catalysts speed up reactions?
They lower the activation energy by providing them a different way for the bond the be broken and remade.
If the activation energy’s lower, more particles will have enough energy to react.
Definition of a catalyst.
A catalyst increases the rate of a reaction by providing an alternative reaction pathway with a lower activation energy. The catalyst is chemically unchanged at the end of the reaction.
How are catalysts used in industry?
Iron is used as a catalyst in ammonia production- if it wasn’t for the iron, temperatures would have to be raised loads to make the reaction happen quick enough- expensive and reduces amount of ammonia produced.
Why are catalysts good for the environment?
Using them means lower temperatures and pressures can be used. So energy is saved, meaning less CO2 is released, and fossil fuel reserves are preserved.
They can also reduce waste by allowing a different reaction to be used with a better atom economy.
What are catalytic converters?
These are made from alloys of platinum, palladium and rhodium. They reduce the pollution released into the atmosphere by speeding up the reaction.
Why are some reactions exothermic?
Exothermic reactions involve bond making.
Bond breaking absorbs energy and bond making releases energy.
More energy released than absorbed.
