Paper 2 - Rates of Reaction Flashcards
what does the collision theory state?
Chemical reactions can only take place when they reacting particles collide of each other. The collisions must have sufficient energy.
overtime why do reactions slow down?
Because the number of reactant molecules is running out, which means we have a small number of collisions per second
The more molecules in a reaction…?
The faster the rate of reaction and more collisions per second
What is a hypothesis?
A proposal that could explain a fact or observation
when is a measurement reproducible?
If it can be repeated by another person or using a different technique or equipment, and still get the same result
what is one problem with the disappearing cross experiment?
Different people have different eyesight
if a solid is in a solution, what can the particles in the solution only react with?
Can only react with the particles on the surface of the solid (on the outside of the solid)
when does the rate of reaction increase?
When we increase the surface area of a solid reactant
how to know if a reaction is exothermic?
The product has less energy than the reactant started with
why does increasing the temperature increase the rate of reaction?
Because it increases the energy of the particles
Catalyst?
increase the rate of chemical reactions but are not used up during the reaction
How do catalysts help us to save money?
because they allow us to carry out reactions quickly without needing to increase the temperature
Can we re use catalysts?
yes because they are not used up in the reaction
How do catalysts increase the rate of reaction?
by providing a different pathway for the reaction that has a lower activation energy (particles require less energy so more particles can collide per second)
why do we not include catalysts in the chemical equation for a reaction?
Because they are not used up in the reaction
Reversible reaction?
this reaction had a different kind of arrow, showing that the products can react to change back to the original reactants
How can we change the direction of reversible reactions?
changing the conditions e.g. heat, cooling
What happens in the reverse reaction?
energy is released so it is exothermic
if a reversible reaction is exothermic in one direction…?
it is endothermic in the opposite direction
equilibrium?
at some point, the forward and the reverse reactions will take place at exactly the same rate
Le Chatelier’s Principle?
if a reaction is at equilibrium and a change is made to the conditions, then the system responds to counteract the change
What happens if we change the concentration of the reactants or products?
then the reaction is no longer at equilibrium
What does the pressure of gas depend on?
The number of molecules
What happens if we increase the pressure on a reversible reaction at equilibrium?
The position of the equilibrium to the side with the smaller number of molecules
e.g. in a reaction, if 4 molecules are on one side of the reaction, and 2 on the other, the position will shift to the 2 molecules
When does changing the pressure have no effect on the equilibrium?
when there is the same number of molecules on each side of the reaction
