Equilibria

• Dynamic equilibrium- the rate of the forward and reversible reaction is equal to each other. The concentration of products and reactants stay constant.
• Equilibrium can only be achieved in a closed system, can be approached from the reactants or the products, is a dynamic process, at equilibrium properties such as temperature and pressure do not change.
• Le Chateliers principle- if a system is in equilibrium, the position of equilibrium will shift to counteract any change in the conditions.
• High pressure sides with fewest moles. Low pressure sides with most moles.
• High temperature favours endothermic reactions. Low temperatures favour exothermic reactions.
• Adding a catalyst has no effect on the equilibrium position. They work by providing an alternative route for the forwards and backward reactions with lower activation energy. Catalysts alter the rate of the forward and reverse reactions equally.
• High enough pressure to increase the yield and rate but low enough for the equipment costs to be manageable as well as to minimise the energy costs of maintaining a high pressure.
• High enough temperature for a fast rate but as low as possible for a better yield.
• For the formation of ammonia: 20000KPa, 650-720K, an iron catalyst with a potassium hydroxide promoter.
• Hydration of ethene to form ethanol: 573K, 6500KPa, a catalyst which is phosphoric acid.
• Reaction of carbon monoxide with hydrogen to form methanol: 500K, 10000KPa, a copper catalyst is used and yield is 5-10%, the unreacted reactants are recycled.
• Kc is the ratio of the concentration of products and reactants at a constant temperature.
• If the forward reaction is exothermic, the value of Kc decreases.
• Equilibrium occurs in a closed system when the rate of the forward reaction is equal to the rate of the reverse reaction.
• High pressure increases the collision frequency, increasing the rate of reaction.
• Homogeneous systems in equilibrium are relevant for Kc.
• If the value for Kc is greater than one the position of equilibrium moves over to the right, and if it's less than one then the position is over the left.