C5.2 Rate Of Reaction Flashcards
What is meant by rate of reaction?
A measure of how quickly reactants are used or products are formed
What formulas can be used to calculate rate of reaction
Amount of reactant used ➗ time taken
Amount of product formed ➗ time taken
What is a gas syringe
Apparatus used for measuring gas volumes
It is made from glass and has graduations marked in cm3
How do you calculate the mean rate of reaction
Gradient = change in volume ➗ change in time
What is a successful collision
A collision that leads to a reaction
A collision between two particles with enough energy for a reaction to happen
Why do reactions go faster and higher temperatures
As the temperature of the reaction mixture increases:
- the particles move more quickly so collide more often
- a greater proportion of colliding particles have the activation energy
The greater the rate of successful collisions, the greater the rate of reaction
What does inversely proportional mean?
When the rate of increase of one variable is the same as the rate of decrease for another variable
What is reaction time
The time taken for a reaction to happen (from the start to the end)
The rate of reaction is inversely proportional to the reaction time
True
Rate of reaction is directly proportional to…
1 ➗ reaction time
Why do reactions go faster at higher concentrations?
The more concentrated a solution is, the more solute is dissolved in the solvent
If a reaction involves one or more reactants in solution, the rate of reaction increases as the concentration increases
This is because:
- particles become more crowded so they collide more often
- the energy store in the particles does not change but because the rate of collisions increases, the rate of successful collisions increases
Why do reactions go faster at higher pressures?
- if a reaction involves one or more reactants in the gas state the rate of reaction increases as the pressure of the gas increases
This is because:
- the particles in the gas state become more crowded so they collide more often
As the rate of collisions increases, so does the rate of successful collisions
Why are reactions faster with larger SA?
For a solid, only particles on their surface can take part in collisions
The rate of reaction increases as the SA does because:
- more reactants particles available for collisions
- collisions more likely and particles collide more often
Why are reactions faster with powders?
- larger SA:VR
- as size of reactant decreases, SA:VR increases
- more frequent collisions
What does catalyse mean
To speed up a reaction using a catalyst
