2.2 Rates Of Reaction Flashcards
What must be true for a particle collision to be successful?
Particles must collide at a certain orientation with an energy greater than or equal to the activation energy
What effect does increasing temperature have on rate of reaction?
Increases rate of reaction because:
- particles have greater kinetic energy
- move a lot faster so collide more frequently
- more particles have energy greater than Ea
What effect does increasing concentration/pressure have on rate of reaction?
Increases rate of reaction because:
- more particles in same volume
- increases number of collision per unit time
- greater chance of successful collisions
What effect does increasing surface area have on rate of reaction?
Increases rate of reaction because:
- only particles on the surface of a solid can collide, more surface area means more particles available to collide
How do we calculate rate of reaction?
Rate = change in concentration or volume / time
What are energy profiles?
Diagrams that represent the enthalpy changes in both exothermic and endothermic reactions
What effect does the addition of a catalyst have on the rate of reaction?
It actually has no effect on the shape of the Boltzmann curve. In fact it just shift the Ea to the left so there a more particles with energy above the Ea
How does a catalyst lower the Ea?
By providing an alternate reaction pathway that has a lower activation energy
What is a Homogeneous catalyst?
Catalysts in the same physical state as the reactants. Take an active part in the reaction and are regenerated
What is a Heterogeneous catalyst?
Catalysts in a different physical state to the reactants. Provides a surface for reactant particles to absorb to, to hold them in place for reaction.
How can the rate of reaction be measured from a change in volume of gas?
Gas can be collected and measured accurately using a gas syringe at regular time intervals during the reaction
How can the rate of reaction be measured from a change in pressure?
If the number of moles of gas differs between reactants and products then pressure change can be measured using a manometer
How can the rate of reaction be measured from a change in mass?
This method is used when one of the heavier gases like CO2 is released during a reaction and allowed to escape. The change in mass can be measured at regular time intervals using an accurate balance.
How can the rate of reaction be measured from a change in colour?
A change in colour can be measured using a colorimeter. A colorimeter can measure the colour change far more efficiently, as it is able to monitor the colour change more accurately and over time using a light sensor.
