The rate and extent of chemical change Flashcards
(13 cards)
what is activation energy
the minimum energy which particles need to collide to start a reaction
how to calculate mean rate of reaction
quantity of reactant used/time taken
OR
quantity of product formed/time taken
Factors affecting the rate of reaction
- concentrations of reactants in solution
-pressure of reacting gases - surface area of solid reactants
- temperature
-presence of catalysts
How does concentration affect rate of reaction and why
A higher concentration means a higher rate of reaction
This is because there are more particles in the same volume, so the particles collide with a greater frequency and there will be a higher frequency of collisions
How does temperature affect rate of reaction and why
A higher temperature means a higher rate of reaction.
This is because particles gain more kinetic energy and move around faster, so particles are more likely to collide, increasing collision frequency of particles. More of the collisions are successful as more have energy greater than the activation energy, increasing rate of reaction
How does increasing pressure of a gas affect rate of reaction
Number of gas molecules in the same volume increase, so the frequency of collisions increase, so rate of reaction increases
how does surface area affect rate of reaction
If solid reactants are in smaller pieces, they have a larger surface area to volume ration. Increasing the surface area of solid reactants increases frequency of collisions and increases rate of reaction
How do catalysts affect rate of reaction
Catalysts increase the rate of reaction, by providing an alternative pathway for the reaction that has a lower activation energy. They are not used up during the reaction
When is equilibrium reached
when the forward and reverse reactions occur at the exact same rate in a closed system - apparatus which prevents the escape of reactants and products
At equilibrium, the amount of reactants and products remain constant
What is Le Chatelier’s principle
If a system is at equilibrium and a change is made to any of the conditions, then the system responds to counteract the change
what is the collision theory
Chemical reactions can only occur when reacting particles collide with with each other with sufficient energy
When a system is at equilibrium and a change is made to any of the conditions, what happens
the system responds to counteract the change
Affect of catalysts on the equilbrium
No effect - they only speed up the forward and backward reactions by the same amount
