rates & equilibrium Flashcards
collision theory
- reactant particles must collide
- reactant must collide with sufficient energy break bonds within reactant molecules
- reactant particles must collide with the correct orientation to break bonds
activation energy
minimum amount of energy needed for a reaction to occur
rate of reaction
comparison of two measurements usually concentration/time (per unit time)
affect of surface area on rate
increased SA = Increased frequency of successful collisions
affect of concentration on rate
increased concentration = increased successful collisions
affect of pressure of gas systems on rate
increased pressure = increased successful collisions
eg. by decreasing volume of a container
affect temp on rate
puts energy into system (kinetic)
greater proportion of particles have sufficient energy
increases number of successful collisions
distribution shifts to right
affect catalyst on rate
provide an alternative reaction pathway
lower activation energy
greater proportion of particles have sufficient energy
increased number of successful collisions
activation energy shifts left
Equilibrium constant expression
[products]^/[reactants]^
factor that can affect Kc
Temperature
K is greater than 10^4
forward reaction / essentially completion
K is less than 10^-4
reaction occurs to a negligible extent / back reaction
K between 10^4 and 10^-4
forward and back reaction occur to a moderate extent
K if equation is reversed, doubled or halved
reversed = 1/K
doubled/tripled = K^2 or K^3
halved = square root of K
Temp effect on K
exothermic = temp increases = K decreases
endothermic = temp increases = K increases
how system shifts when
K>Q
K
K>Q —- shifts right
K
K increases
K decreases
forward reaction more favoured
back reaction more favoured
le chatelier’s principle
if an equilibrium system is subjected to change, then the system will shift in a direction that partially opposes that change
changes to an equilibrium system
- change in temp
- adding a catalyst
- adding an inert gas
- add reactant/remove product
-remove reactant/add product
- increases temp: exothermic-> shifts left; endothermic-> shifts right
- adding a catalyst: no change (rate of each reaction increases equally)
- adding an inert gas: no change
- add reactant/remove product: shifts right
- remove reactant/add product: shifts left
size of relative gradients?
2NO2
N2O4
2NO2 has double as steep gradient as N2O4 because of the 2:1 mole ratio in the equation
