Unit 6 - Rate And Extent Of Chemical Change Flashcards
How to work out mean rate of reaction
Quantity of product or reactant formed / time taken
What is collision theory
Chemical reactions can only take place when the reacting particles collide with each other. The collisions must have sufficient energy. The rate of a chemical reaction is determined by the frequency of successful collisions
What does frequency mean in collision theory
Means the number of successful collisions per second
What happens when a solid reacts with a solution in terms of particles
The particles in the solution can only react with particles on the surface of the solid
How does surface area affect rate of reaction
We have more collision per second so rate will increase when surface area is increased
How does surface area to volume ration affect rate of reaction
Smaller sized blocks of solid reactant have a great surface area to volume ratio than large blocks, this means more particles on the surface so there are more collisions per second so increased rate of reaction
What happens if two particles with small amounts of energy collide
Because they have low energy they cannot overcome the activation energy barrier, so they would not collide successfully and no reaction would occur
What happens if two particles both with large amounts of energy collide
They have enough energy to overcome the activation barrier and collide successfully, a reaction would take place
How does temperature affect rate of chemical reactions
-increases the rate of reactions
-as increase temperature will increase energy in particles
-as they have more energy they can move faster
-this increases frequency of collisions, there is a greater number of collisions per second
-each collision has more energy so more particles can overcome activation barrier and collide successfully
What is a catalyst
Increase the rate of chemical reactions but are not used up during the reaction
Advantages of catalysts
Allow us to carry out reactions quickly without needing to increase temperature so they save money, as they are not used up during a reaction we can reuse them
How do catalysts affect rate of reaction
Increase the rate by providing a different pathway for the reaction that has a lower activation energy so less energy required to cross activation energy barrier so more particles successfully collide per second
Why don’t we include catalysts in the chemical equation for a reaction
They are not used up in the reaction
How do we know if a reversible reaction is Exothermic or endothermic
Is a reversible reaction is Exothermic in one direction it is endothermic in the opposite direction ,the same amount of energy is transferred in each case
What is equilibrium
The forward and the reverse reactions will take place at the exact same rate this point is equilibrium
