3.2.3 Chemical Equilibrium Flashcards Preview

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Flashcards in 3.2.3 Chemical Equilibrium Deck (15)
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Conditions for Dynamic Equilibrium

-Closed system
- rate of forwards reaction is equal to the rate of reverse reaction
-concentrations of forwards and reverse reactions stay constant over time (don't change


Le Chatelier's Principle

equilibrium shifts to oppose any changes to the system's conditions (only for homogeneous equilibria)


Homogeneous Equilibria

all products and reactants in the same phase


Le Chatelier's and Concentration

increase concentration of reactants, equilibrium shifts to right to oppose the change, more products made
increase concentration of products, equilibrium moves left to oppose change, more reactants made.


Le Chatelier's and Pressure

increasing the pressure will cause equilibrium to move to the side with less gaseous molecules to reduce pressure (vice-versa)


Le Chatelier's and Temperature

increase the temp the equilibrium moves favour more endothermic reaction
decrease the temp. the equilibrium moves to favour more exothermic reaction


Le Chatelier's and a Catalyst

a catalyst doesn't affect equilibrium position, it speeds up the rate of reaction for both forward and reverse reaction equally.
speeds up rate at which equilibrium is reached


Le Chatelier's Principle making ethanol

ethene(g) + H2O(g)< -> ethanol (g) (-46kjmol-1)
pressure= 60 atm
temp= 300 C
catalyst= phosphoric acid


Making Ethanol Compromises

low temps would mean a higher yield of ethanol but low temps mean a slower rate of reaction (300C is a compromise between yield and rate)
high pressures would mean a higher rate and higher yield, high pressures need expensive, thick vessels and are dangerous. (compromise between yield/rate and cost)



Equilibrium Constant


Kc calculation

product conc/ reactants conc


Interpreting Kc values

if Kc > 1 = equilibrium shifted more to products
Kc < 1 = equilibrium shifted more to reactants


Changing Kc values

Only temperature can affect Kc values
temp change causes eq to more right = Kc increases
temp change causes eq to move left = Kc decreases


Investigating Equilibrium- changing conc

Fe3+(aq) + 3SCN+(aq) Fe(SCN)3 (aq)
yellow colourless blood red


Investigating Equilibrium- changing temp

2NO2 (g) N2O4 (g) (forwards exo, backwards endo)
brown colourless
(place in warm and cool water baths)