Topic 12 - Reversible Reactions and Equilibria Flashcards
4.14 - What are reversible reactions?
When products can reform the reactants and the forwards and backwards reaction are at the same rate.
4.14 - What is dynamic equilibrium?
During a reversible reaction the amount of reactants and products change. After some time, the forward and backwards reaction are still occurring but the percentage of reactants and products are no longer changing. This is dynamic equilibrium as the reactions are still occurring ( dynamic ) and the substances are in balance ( equilibrium ).
Dynamic equilibrium only happens in a closed system, when there is no loss or reactants and products, as in an open system, gases would escape and equilibrium wouldn’t be achieved.
4.15 - How is ammonia formed?
Ammonia is manufactured by the Haber process, involving a reversible reaction between nitrogen from air and hydrogen from natural gas that reaches dynamic equilibrium. This equilibrium position is dependent on the reaction conditions, the conditions which favour the forward reaction are chosen to make a large amount of product as cheaply as possible.
4.16 - What are the conditions for the Haber process?
temperature 450 °C
pressure 200 atmospheres
iron catalyst
4.17 - How do changes in temperature, pressure and concentration affect the equilibrium position?
Increasing temperature - equilibrium shifts to the endothermic direction ( energy transferred from the surroundings ).
Decreasing temperature - equilibrium shifts to the exothermic direction ( energy transferred to the surroundings ).
Increasing gas pressure - equilibrium shifts in the direction forming fewer gas molecules.
Decreasing gas pressure - equilibrium shifts in the direction forming more gas molecules.
Increasing concentration - equilibrium shifts in the direction using up the substance added.
Decreasing concentration - equilibrium shifts in the direction forming more of the substance that has been removed.
