10/11 Equilbrium Flashcards
Dynamic equilibrium
The rate of forward reaction equals the rate of the reverse reaction
1) relative conc of reactants and products remain constant
2) only occurs in a closed system
Equilibrium is reached when….
Concentration, colour, density, pressure is constant
Le Chatelier principle and conditions
If conditions of a dynamic equilibrium in a closed system are changed, the equilibrium shifts to oppose the change
2) conditions: conc/pressure/temp
What is a closed system
No reactants or products can escape
What effect does catalyst have on position of eq
No effect on position, but system reaches eq more quickly
Pressure
1) Only affects dynamic eq that contains at least 1 gas
2) Prediction of shift dependent on total no. Moles of gas on each side of eq
3) increase pressure: moves to side with less moles of gas
4) decrease pressure: moves to side with more moles of gas
5) no of moles of gas on each side equal, then changes in pressure have no effect on position of eq
Temperature
1) increase in temp favours endothermic reaction
2) decrease in temp favours exothermic reaction
3) if deltaH=0 then changes to temp have no effect on position of eq
Haber process: actual conditions
N2(g) + 3H2(g) —> 2NH3(g) exothermic
1) high conc of nitrogen and hydrogen: unreacted are recycled to maintain a high conc
2) low conc of NH3 - reaction mixture cooled and condensed and constantly removed
3) compromise temp: low temp increases yield but ROR decreases so compromise used to balance yield and rate
4) compromise pressure: High pressure increases yield and rate but very expensive and dangerous
5) catalyst increases rate but no effect on yield
Kc expression
Describes state of eq with respect to conc of reactants and products
Homogenous
All same phase (g) or (aq)
Solids and liquids cannot have conc
Heterogenous
More than one phase
Only accounts for (g) and (aq)
If Kc = 1
Eq is equally divided in the middle
If Kc<1
Eq lies to left - favours the reactants
If Kc>1
Eq lies to right (favours the products)
Kp the eq constant
Describes the state of eq with respect to the partial pressures exerted by the reactants and products (gases only)
