Dynamic Equilibrium Flashcards
Reversible reactions
Both forward and backward reactions occur at the same time
Dynamic equilibrium
Rate of forward is equal to the rate of the reverse reaction
Conc of reactants and products do not change
To be in equilibrium, must be in a closed system
Le Chatelier’s principle
When a system in equilibrium is subjected to external change, system readjusts to minimise effect of change
Effect of concentration changes
More products formed, p of e => if there is an increase in reactant
More reactant formed, p of e <= if there is an increase in product
Investigating concentration changes
2CrO4 2- + 2H+ <=> Cr2 O7 2- + H2O
Yellow. Orange
Add sulphuric acid, orange, increase in H+, more product formed
Add sodium hydroxide, yellow, increase in water, more reactant formed
Effect of temperature changes
Increase temp, p of e => endo
Decrease temp, p of e => exo
Forward and reverse directions have opposite enthalpies
Investigating temperature changes
-∆H Co(H2O)6 2+ +4Cl- <=> CoCl4 2- +6H2O +∆H
Pink. Blue
Hot water bath, blue, move to right, cool down
Ice water, pink, move to left, heat up
Effect pressure changes
Increase pressure, p of e moves to side with fewer moles
Decrease pressure, p of e moves to side with more moles
Investigating pressure changes
2NO2 <=> N2O4
Brown. Colourless
Catalysts and equilibrium
No effect on p of e
Increase rate of forward and backward
Increase rate at which equilibrium is established
Haber process
N2 + 3H2 <=> 2NH3 ∆H=-92kj mol-1
Ideal conditons, low temp, rate too slow
High pressure, safety and failure in steelworks is fatal
Compromise made 350-500C, 100-200atm, iron catalyst
Good yield achieved quickly
