| What is a reversable reaction | reactants react to form products (Forward) which reacts to form reactants (REverse)
conc of reactants first decreases until it plateaus while the conc of products at the start is 0 but increases as well and flattens at equilibrium |
| What are the factors needed for equilibrium to occur? | rate of forward = rate of reverse
both occuring at the same time (dynamic)
conc of R and P remain constant but not equal
conc depends on how much of each substance there is in the beginning
no change in macroscopic properties like color or pH
EQ can be reached from either direction
only happens in closed systems |
| What is physical equilbria? | happens with a change in state (bw liquid and vapour) |
| Describe the process of evaporation (physical equilibrium) | endothermic bec particles have to overcome intermolecular forces
higher kinetic energy molecules will overcome the forces first =
average KE decreases = temp decreases
heat is drawn in from surroundings for more molecules to evaporate
as molecules of vapor start to come from evaporation some re-enter the liquid (condensation)
as the no of molecules in a vapor phase increases = condensation rate increases
when cond = evap rate (dynamic equilibrium) = color of vapor is constant |
| What is eq position? | relative amounts of reactants and products present at eq as it doesnt mean 50 % reactants and 50% products |
| What is la chatelier's principle? (2) | used to predict the effect of a change in conditions on equilibria
bec the system responds to change by minimizing the effects
changes made can be on conc, p , or temp |
| How does concentration affect equilibrium position? | moves to decrease the concentration
so if the reactants conc was increased = eq position would move to the right (products side) to decrease it
KC value doesnt change |
| How does temperature affect equilibrium position | when the reaction is endothermic: increasing temp will move it in the endothermic direction (shifts to right) = more products present
but in an exothermic reaction, increasing the temp would shift the eq position to the left bec the reverse reaction would be the endothermic reaction = more reactants |
| How does pressure affect eq position | shift depends on the no of moles on each side as it will shift to the side with the fewest no of moles
when there is a same number of moles on each side changing the pressure will have no effect on the eq position
pressure only affect gases and not solids |
| How do catalysts affect eq position? | catalysts increase the rate of a chemical reaction without being used in the reaction
they work by giving an alternative pathway at lower activation energy
doesn't have an effect on equilibrium position or KC value bec the rate of forward and backward reaction increase equally = only reduces time taken to reach equilibrium |
| What is Kc? (8) | A constant for a specific reaction at a specific temp to determine how far a reaction will occur
KC and Q have the same formula but KC uses concentration of equilibrium for the reactants and products
if conc isnt given : mol / vol
[products] no of moles
-----------------------------
[reactants]no of moles
there can be diff values of KC for the same reaction it just depends if youre looking at the forward or reverse reaction
ONLY affected by temperature
endothermic: increasing temp will shift it to the right so KC value increases
exothermic: shifts to the left so the value of KC decreases |
| What is the reaction quotient? | direction the reaction will happen to reach equilibrium by giving the ratio of the concentration of the reactant anf the products
uses non eq concentration
system at eq = Q = Kc
conc = moles / volume
if Q < Kc = continues to the right to increase Qs value
if Q > Kc =continues to left to decrease Qs value |
