reaction rates Flashcards
activation energy
the minimum amount of energy required for a successful collision to occur
for a reaction to occur
- particles must collide
- particles must possess enough energy (E >= Ea)
rate of reaction
total change in amount of reactant or product / time taken
How to monitor the rate of reaction
- gas syringe
- measuring cylinder over water
- change in mass
- change in temp
- colour of solution
interpreting a vol of gas produced over time graph
- fastest rate of reaction - most successful collision - most amount of reactant
- gradient less steep - less successful collisions
- reaction stops - no more reactant (limiting used up) no successful collisions
factors effecting rate
- temp
- amount of reactants
- presence of catalysts
- surface area
effect of concentration on rate
increasing conc increases rate
- more particles in the same vol
- more frequent collisions
- % of successful collisions the same
(rate and conc directly proportional)
conc graph - excess reactant conc increased
- rate increases
- amount unaffected
conc graph - limiting conc increased
- rate increases
- product made increases
affect of temp on reaction rate
- particles gain KE and move faster
- frequency of collisions increases
- greater % of particles have E>= Ea
- greater % of successful collisions
(rate varies exponentially with temp)
temp graph
- steeper gradient (faster rate)
- total amount of gas not effected
affect of surface are on rate
- smaller particle size = bigger surface area
- move surface available for reactions to take place on
- more frequent collisions
surface area graph
- steeper gradient (faster rate)
- no affect on amount of CO2
catalyst
speeds up the rate of reaction without being used up
catalyse effect on rate
- lower Ea by providing an alternate reaction pathway
- so proportion of successful collisions with E>= Ea increases
catalyst graph
- same amount of gas made
-steeper (faster rate)
reversible reaction
CuSO4. 5H2O <-> CuSO4 + 5H2O
dynamic equilibrium
if there is a closed system
- forward and reverse reactions occur at same rate
- conc of reactants and products remain constant
position of equilibrium
proportions of various substances in equilibrium mixture
A + B <-> C + D
- if high proportion of C moves to right
- if high proportion of B moves to left
shifting position of equilibrium
if there’s a change in the system the position shifts to oppose the change
factors :
- conc
- pressure
- temp
changing conc - on position of equilibrium
A + B <-> C + D
add more A - moves right
moves to side with lower conc
changing pressure - on position fo equilibrium
A + 2B <-> C + D
(3 mol). (2mol)
increasing pressure shifts to side with less moles
decreasing moves to side with more moles
implications of changing pressure
expensive to increase p + dangerous
slow rate of decrease p
changing temp - on position of equilibrium
A + B <-> C + D
-> exo
<- endo
increasing the temp will shift in the endo direction
decreasing will shift to exo side
