THE RATE AND EXTENT OF CHEMICAL CHANGE Flashcards
(23 cards)
2 equations for rate of reaction
quantity of products formed / time taken
quantity of reactants used / time taken
factors that affect the rate of chemical reaction (4)
temperature
concentration/pressure
surface area
catalyst
what is collision theory
for particles to react, they have to collide with eachother with sufficient energy (activation energy)
most important word in this topic
FREQUENCY
how does temp affect rate of reaction
high temp -> particles gain more energy -> move faster + collide with more energy -> collide more frequently + more likely to exceed the activation energy
higher rate of successful collisions
how does concentration and pressure affect rate
conc/pressure increase -> more particles per unit volume -> collisions more frequent
how does surface area change the rate of reaction
higher surface area : volume ratio -> higher frequency of collisions
how does catalyst change the rate of reaction
lowers the activation energy by altering the reaction pathway so then higher proportion of successful collisions
do forwards and backwards reactions of the same reaction have the same rate
no
does heating speed up the forwards or backwards reaction
forwards
does cooling speed up the forwards or backwards reaction
backwards
equilibrium can only be reached when the reaction is in what type of system
closed system
anhydrous means …
no water present
endothermic reactions require what
heat energy from the surroundings
what is le chateliers principle
if the conditions are changed in a reversible reaction, the position of equilibrium will shift to try and counteract the change
hoe does increasing temp affect equilibrium
if forward reaction is ENDOTHERMIC , equilibrium shifts to the right ( more products formed
if forward reaction is EXOTHERMIC, equilibrium shifts to the left (more reactants formed
How does increasing pressure affect equilibrium?
The equilibrium shifts to the side with fewer gas molecules to reduce the pressure.
What effect does a catalyst have on equilibrium?
NO EFFECT
What happens when you increase the concentration of reactants?
The equilibrium shifts to the right to produce more products and reduce the concentration of reactants.
At equilibrium, if there are more products than reactants, we say that the position of equilibrium lies:
to the right
What are the three factors that affect the position of equilibrium?
temp
conc
pressure
An increase in pressure moves the position of equilibrium to whichever side has the:
smaller no of gas molecules
2NO2(g) ⇋ N2O4(g) (-24 kJ mol-1)
In the reaction above, the (-24 kJ mol-1) tells us that the forward reaction is:
exothermic (negative enthalpy values mean the reaction is exo)
