Rates Of Reaction Flashcards
What is a catalyst?
A substance that speeds up chemical reactions without being used up or chemically changed
Why use a catalyst? (3)
- reactions take place at lower temperatures and pressures
- reduces energy usage
- saves time and money
What needs to happen to atoms for a reaction to happen?
Groups of atoms need to collide
What is the activation energy?
The minimum energy needed for a reaction to happen
How can the rate of reaction be increased? (4)
INCREASE:
- Temperature
- Concentration
- Pressure
- Surface area
How does concentration increase the rate of reaction?
More particles increases the number of reactant particles in the same volume
More collisions per second
How does surface area increase the rate of reaction?
When in a large lump (small sa) only the outer particles are exposed
When in small pieces (large sa) every particle is exposed and can react
How does temperature increase the rate of reaction? (2)
More energy means more successful collisions
The speed increases, meaning more collisions per second
What is the rate?
The speed at which reactants are turned into products
What are reactants?
A substance that takes part in a change during a reaction
What is a precipitation reaction?
When you mix two see through solutions to produce a precipitate, which clouds the solution
How do you know if a reaction is a precipitation reaction?
It is a very fast reaction
What is an example of a very slow reaction?
The rusting of iron
What is used to measure gas volumes accurately?
A gas syringe
How do catalysts work?
They provide an alternative reaction route which requires less activation energy
What is a reaction profile?
A graph that shows the energy changes with and without a catalyst in an exothermique reaction
What is an exothermic reaction?
The making of bonds
What is an endothermic reaction?
The breaking of bonds
What is the method for showing how surface area affects rate which uses a gas syringe?
- Add measured amount of marble chips
- Add measured amount of hydrochloric acid
- Put in rubber bung with glass tube
- Connect gas syringe
What is the method for showing how surface area affects rate which uses cotton wool?
- Add measured amount of marble chips
- Add measured amount of hydrochloric acid
- Put cotton wool in top to allow gas out
- Measure mass every 20 seconds
What are 2 sources of error in the precipitation reaction?
Not easy to see when cross disappears
The temperature changes as the reaction proceeds
How can you reduce the errors of a precipitation reaction?
Conduct the reaction in the water so the temperature doesn’t change
Use a colorimeter
What is dynamic equilibrium?
When the forwards and backwards reactions in a reversible chemical reaction which occur at the same rate
