Module 3 + 5: Rate of reaction and equilibrium Flashcards
In order to react, two particles must …
Collide with a certain amount of KE. They need to collide with correct orientation and have sufficient energy to overcome activation energy.
How does increasing concentration affect rate of reaction?
Increases - more particles in a given volume so more frequent collisions, successful.
How does increasing pressure affect rate of reaction?
Increases - more gas particles in a given volume, pushed closer together, more frequent successful collisions.
Surface area of …
Reactants also affect rate of reaction.
2 ways of monitoring the rate of reaction?
- Removal of reactant.
- Formation of product.
2 ways of monitoring rate of reaction for gases?
- Volume of gas produced at regular intervals using gas collection e.g. gas syringe, measuring cylinder.
- Loss of mass of reactants using a balance.
Experiment to monitor gas rate of reaction?
Reactant solution is added to conical flask and a bung is replaced. Initial volume in measuring cylinder is recorded. Immediately start stopwatch and take the volume of gas produced at regular intervals until reaction is complete/no more gas is produced.
Define activation energy.
Minimum amount of KE needed to react and break the bonds to start the reaction.
Define catalyst.
Increases rate of reaction by providing an alternative pathway with a lower activation energy for bonds to be broken and remade. Catalysts are chemically unchanged at the end of a reaction.
Iron catalyst is used to …
Make ammonia in the Haber process.
What is a heterogenous catalyst?
Has a different physical state to the reactants. They are usually solids with gaseous or aqueous solutions.
Where does the reaction happen on a heterogenous catalyst?
Reactant molecules are adsorbed (weakly bonded) to the surface of catalyst, where the reaction takes place. Products leave surface of catalyst by desorption. Increasing SA increase no. molecules reacting at the same time.
Examples of heterogenous catalysts?
Fe (s) in the Haber process to make ammonia.
How does a catalytic converter work?
Has a large surface area for heterogenous catalysis to convert harmful exhaust fumes into less harmful gases that can be released into the atmosphere. CO and NO2 into CO2 and N2 gas.
What is a homogenous catalyst?
Same physical state as reactants. The catalyst is usually in aqueous form between two aqueous solutions.
How does a homogenous catalyst work?
The reactants react with the catalyst to make an intermediate species, which breaks down to form products and reform the catalyst.
How are catalysts sustainable?
Lower temps and pressures can be used, as they lower activation energy. Energy is saved, less CO2 is released, fossil fuels are preserved. Catalysts also reduce waste and better atom economy. It also cuts costs.
You can work out reaction rate from …
The gradient of the graph.
