6. Rates of Reaction Flashcards
Rate of reaction
How fast the reactants are changed into products
Graphs: steeper gradient:
Faster rate of reaction
Graphs: flat line
Reaction has finished
Collision theory
- collision frequency
- energy transferred [successful collision]
Activation energy
minimum amount of energy the particles need to react
Factors which increase rate of reaction
-temperature
-concentration/pressure
-SA (big chunks or powder)
-catalyst
Increasing temperature:
- particles move faster
-more collisions
-increase energy of collisions
-more successful collisions
-increased rate of reaction
Increasing concentration [solutions]:
-more particles of reactant in the same volume
-collisions more likely
Increasing pressure [gas]:
-particles are more crowded
-frequency of collisions will increase
Increasing SA [smaller solids]:
-increase SA:V ratio
-particles around solid will have more area to work on
-frequency of collisions will increase
Adding a catalyst:
-decrease activation energy
-by providing alternative pathway
-more particles have at least the minimum amount of energy for reaction to occur
Catalyst
increase reaction rate without being used up
rate of reaction formula
amount of reactant used up or product formed/ time
Precipitation method:
Disappearing Cross Method:
1. mixing two colourless solutions which produce precipitate [cloudy]
2. time the time it takes until the cross is no longer visible
The result is subjective- different people may not exactly agree on when the mark ‘disappears’
Change is mass [gas] method:
mass balance measures change in mass: gas released
Volume [of gas] given off:
use gas syringe to measure volume of gas released per time
Marble chips & HCl experiment [SA:V]
-same concentration and volume of HCl
-different SA of marble chips
Marble chips & HCl experiment [concentration]
-same mass and SA of marble chips
-different concentrations of HCl.
Decomposition of hydrogen peroxide experiment [catalyst]:
- add MnO2 power (catalyst) to the hydrogen peroxide
- measure the volume of gas (O2) produced at a regular time period
- repeat experiment with different catalyst
Decomposition of hydrogen peroxide formula
hydrogen peroxide (aq) -> water (l) + oxygen (g)
