Rates And Equilibrium Flashcards
How do you measure the rate of a reaction?
Measure the rate of a reaction you can:
•Measure how fast the reactants are used up
•Measure how fast the products are made
(E.g. measure mass lost due to gas formed, measure volume of gas made, measure time for insoluble product to form etc.)
What is the equation for rate?
Rate (cm3/secs) = volume of gas / time
Describe the gradient of a reaction
1) Beginning - step gradient, fastest reaction rate
2) Middle - gradient decreases with time, reaction rate slows
3) End - gradient becomes zero, shows reaction has stopped
What is collision theory?
- For a reaction to happen reactants must:
collide with enough energy (activation energy) - A successful collision is one that leads to a reaction
How do you increase the rate of reaction?
- Increase the frequency of collisions
- Increase the energy of the collisions
- Decrease the energy needed for a collision to be successful
Name some factors that affect the rate of reaction?
- Concentration and Pressure
More particles in the same space.
More frequent collisions - Surface area
More particles available to react.
More frequent collisions - Temperature
Particles move faster.
So they collide more frequently.
Particles collide with more energy.
So more of the collisions are successful. - Catalysts
Lower the energy needed for successful collisions. (Activation energy)
Not used up.
Biological catalysts are called enzymes
What are reversible reactions?
- Can go in both directions
- If a reaction is exothermic in one direction it is endothermic in the other direction
What is a closed system?
In a closed system (where nothing can get in or out) an equilibrium is reached where the rate of reaction is the same in both directions.
What happens at equilibrium?
At equilibrium:
- Rate of forward reaction = rate of reverse reaction.
- Mount of products and reactants don’t change.
