Rates of reaction Flashcards
What is the rate of a reaction?
The speed at which a reaction occurs (at a certain time)
What is the collision theory?
Reactants have to collide with enough energy (activation energy) for a reaction to occur
Disadvantages/advantages of using mass lost as way to measure rate of reaction?
advantage:
reliable
disadvantage:
set up makes it inaccurate
Disadvantages/advantages of using collecting gas underwater as way to measure rate of reaction?
advantages:
easy to set up
good for slower reacting
disadvantages:
inaccurate - hard to read gas volume
some gases (eg CO2) are soluble in water
Disadvantages/advantages of using gas syringe as way to measure rate of reaction?
advantages:
accurate reading of gas volume
disadvantages:
leaks are possible
Disadvantages/advantages of using disappearing cross as way to measure rate of reaction?
approximation for initial rate of reaction:
Na2S2O3(sodium thiosulphate) + 2HCl -> 2NaCl + S + SO2 + H2O
disadvantages:
judged by eye - unreliable
reaction time
Explain how a reaction starts to finishes.
Reactions start fast = lots of reactant available
Reaction slows down = reactants get used up
Reaction stops = reactant has been used up
How to calculate rate of reaction?
change in reactant or product / time taken
How can you increase the rate of a reaction?
increase temp, pressure, surface area, concentration, use catalyst
What is concentration?
measure of number of particles in a certain volume
How does increasing surface area increase rate of reaction?
- increasing SA increases rate
- as particles get smaller, SA increases
- more of reactant is exposed
- more frequent collisions, more successful collisions per unit time
How does increasing temperature increase rate of reaction?
- increasing temperature increases rate
- particles have more kinetic energy
- more collisions occur with required activation energy
- more successful collisions per unit time
How does increasing concentration increase rate of reaction?
- increasing concentration increases rate
- more particles in the same volume
- more frequent collisions
- more successful collisions per unit time
How does increasing pressure increase rate of reaction?
- increasing pressure increases rate
- same number of particles in a smaller volume
- more frequent collisions
- more successful collisions per unit time
How does the presence of a catalyst increase rate of reaction?
- using a catalyst increases rate
- catalyst provides alternative route with a lower activation energy
- more collisions occur with required activation energy
- more successful collisions per unit time
