C8 - Rates And Equilibrium Flashcards
E. Mean rate of reaction?
Quantity of reactant used / time
OR
Quantity of product formed / time
How to calculate the rate of reaction at a specific time? (On a graph)
Draw a tangent!!!
Gradient of the line shows…
Rate at that time.
D. Activation energy.
The minimum amount of energy that particles must have before they can react.
What increases the rate of reaction?
- Surface area
- Pressure
- Temperature
- Catalyst
- Concentration
Why does increasing the surface area of a reactant increase the rate of reaction?
Because it means more particles are exposed and so the number of collisions increases, and so the number of successful collisions increases.
Why does increasing the temperature increase the rate of reaction?
Because particles collide more often, meaning there is more successful collisions. Also the particles collide with more energy so an increases proportion of particles exceeding the activation energy has a greater effect on rate then increased frequency of collisions.
Why does increasing the concentration of reactants increase the rate of reaction?
Increases the frequency because there is more particles, and so increases the number of successful collisions, which increases the rate.
Why does increasing the pressure increase the rate of reaction?
Because the particles are colder together, so the number of collisions increases, and so does the number of successful collisions.
What do catalysts do?
Speed up the rate of the reaction, but not used up in the reaction - remains chemically unchanged. So can be used more then once.
Catalysts are used to….?
Increase rates and reduce energy cost.
Increasing pressure favours…
reaction that forms fewer gas molecules
Decreasing pressure favours…
reaction that forms more gas molecules
Increasing temperature favours….
endothermic reaction
Decreasing temperature favours…
exothermic reaction
