Equilibria -4
- Created by: Shannon
- Created on: 02-04-15 15:02
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- Equilibria
- Dynamic equilibria
- The rate of forward and backward reactions are equal
- No further changes in concentration
- Occurs in a close system
- General rules
- Heat favours the endothermic direction
- Increasing pressure will shift equilibrium to the side with the fewest particles
- On the addition of a reactant or product, equilibrium will shift in the direction that will reduce its effects and conversely
- Equilibrium constants
- The equilibrium constant measures the extent to which a reversible reaction will occur at a given temperature
- Kc = concentration of products / concentration of reactants
- Can be measures in terms of concentration (Kc) or partial pressures (Kp)
- Kp = p(products) / p(reactants)
- Partial pressure = mole fraction x total pressure
- Mole fraction = moles of chemical species / total number of moles
- Partial pressure = mole fraction x total pressure
- Total and entropy change and the equilibrium constant
- total entropy = R lnK
- This means that as a change in temperature causes a change in the total entropy, the value of the equilibrium constant will change too
- Exothermic reaction - increase in temp will cause entropy of surroundings to be less +ve = total entropy smaller = K smaller
- Endothermic reaction -increase in temp will cause entropy of surroundings to be less -ve = total entropy larger = K larger
- This means that as a change in temperature causes a change in the total entropy, the value of the equilibrium constant will change too
- total entropy = R lnK
- Le Chatelier's principle
- If a system at equilibrium is disturbed, the the position of equilibrium will shift to oppose the effects of the change, and restore equilibrium
- Dynamic equilibria
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