5B - Equilibria
- Created by: Strelly22
- Created on: 14-10-21 20:19
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- 5B - Equilibria
- Dynamic equilibrium
- the equilibrium that exists in a closed system when the rate of the forward reaction = the rate of the reverse reaction and concs don't change
- closed system = no material is added / removed and conditions don't change
- Le Chateliers' principle
- le chateliers principle = when a system in dynamic equilibrium is subjected to an external change, the system adjusts itself to minimise the effects of the change and to restore equilibrium
- add more reactant ? shift right, make more product
- remove product ? shift right, make more product
- increase temp ? move to endo side as absorb heat energy
- increase pressure ? shift to side with fewer moles to reduce pressure
- add more catalyst ? no change, reach equilibrium quicker
- Kc
- aA + bB ?? cC + dD
- Kc = ([C]^c x [D]^d ) / ([A]^a x [B]^b)
- [] = conc
- mol dm^-3
- Kc is constant at a given temperature
- Find Kc using a RICE table
- 1)Ratio 2)Initial moles 3)Change in moles 4)Equilibrium moles 5)Equilibrium conc
- Kp
- p = partial pressure of the component at equilibrium
- aA (g) + bB (g) ?? cC (g) + dD (g)
- Kp = [p(C)^c x p(D)^d] / [p(A)^a x p(B)^b]
- Kp is constant at a given temperature
- partial pressure of a gas = the pressure exerted by a gas in a mixture , if it alone occupied the whole container
- total pressure of all gases in a mixture = sum of partial pressures of each component
- mole fraction of a given gas = moles of a given gas / total moles of all gases
- partial pressure = mole fraction x total pressure
- sum of all mole fractions = 1
- mole fraction = moles of gas of interest / total moles of all gases
- Heterogeneous equilibria
- homogeneous equilibria = equilibrium in which all the species making up the reactants and products have the same physical state
- heterogeneous equilibria = equilibria in which the species making up the reactants and products have different physical states
- Kc expressions exclude (s) and (l). only include (aq) or (g)
- Kp only include (g)
- Also see 'choosing industrial conditions
- Dynamic equilibrium
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