Equilibrium Systems Flashcards
(58 cards)
Whats a equilibrium and when does it occur
a balance point of rxn occurs in closed system and constant temperature
When is equilibrium reached
- colour constant
- Rate of fwd rxn = Rate of reverse rxn
- concentrations all constant
- all measurable properties are constant (temp vol ph Conc pressure)
4 Types of equilibrium
1- Quantitative >99% reverse rxn negligible
2- Non spontaneous 0% no products observed
3- Products favoured >50% more products
4- Reactants favoured <50% less products than reactants
What applies to a system at equilibrium
Rate fed rxn = Rate of reverse rxn
What is phase equilibrium
More than one phase exists at a equilibrium in closed system
What is solubility equilibrium
equilm between undissolved solids and ionic species in solutions; solids continue to dissolve and ion-pairs continue to form solids; the rate of
dissolving = rate of
precipitation
Whats a chemical equilibrium
rxn of more than one substance show with double arrows
what are all reverse rxns based on , meaning
collision reaction theory
atoms in constant random motion so they collide breaking and forming bonds
When is a dynamic equilibrium occurring
- both processes occur at sane rate
- microscopic level
A shift right means
rxn moves towards products forward rxn
less reactants and more products so Products favoured
A shift left means
moves to the reactants
reverse rxn
more reactants than products
so reactant favoured
two ways to show position of equilibrium
1- % rxn or % yield
2 - Equilibrium constant Kc
What is Kc
- what does it tell u
- what changes it
- K > 1 prod fav , K<1 react fav , K = 1 neither fav
- only changing temp changes it
How to write Kc from a balanced equation : rules
- coefficient becomes exponent
- products over reactants
- leave out all solids
- leave out liquids unless all liquid
- include aq and gasses as their conc can change
What is heterogeneous equilibrium
when products are different phase than reactants
what’s homogeneous equilibrium
when products are same phase as reactants
Calculating equilibrium done with
steps
ICE tables
R- write rxn
I- initial conc
C- change represented by x
E- equilibrium conc
What’s the approximation rule
If [initial]/ Kc is bigger or equal to 1000 u can take out the unknown (x) from only the denominator in Kc expression to help solve
When to use Quadratic formula
If approximation rule disent work and you need to solve for x
What is the Le chat principle used for
modelling the initial equilibrium and the change due to the stress that formed the new equilibrium
The equilibrium constant K is only affected by
temperature
What does a Le chat change in concentration look like
- stress is
- looks like
- shift
- K
Stress is either removing or adding a part ofcthe system so creates a spike up or down suddenly
Shifts right or left to fill hole or even out spike depending on if adding or removing
K is not affected
What does a change in temperature look like in le chat graph
- reaction results
- stress
- K
Change in reactants will oppose the products
Stress is adding heat so it will shiftctocspread heat out gradually
K is affected only by temperature
What does a change in pressure/ volume look like
- stress
- results
- equal vs unequal mols
- shift
- affects on different states
Change in pressure result of change in vol
- If mols equal will affect whole system in the same way no shift
- If mols unequal will shift to even out pressure
- more mol = more pressure
- liquids and solids not affected otr adding gas or catalyst
