7.3 The Position Of Equilibrium Flashcards
What does the position of equilibrium refer to?
The relative amounts of reactants and products present at equilibrium.
What is Le Chatelier’s principle?
If a system at equilibrium is subjected to some change the position of equilibrium will shift in order to minimise the effect of the change.
What happens to equilibrium and Kc when the pressure has been increased?
Position of equilibrium shifts to side with fewer moles of gas, no change in Kc.
What happens to equilibrium and Kc when the pressure has been decreased?
Position of equilibrium shifts to side with more moles of gas, no change in Kc.
What happens to equilibrium and Kc when the temperature has been increased?
Position of equilibrium shifts in endothermic direction, if the reaction is exothermic the value of Kc decreases, if the reaction is endothermic the value of Kc increases.
What happens to equilibrium and Kc when the temperature has been decreased?
Position of equilibrium shifts in exothermic direction, if the reaction if exothermic the value of Kc increases, if the reaction is endothermic the value of Kc decreases.
What happens to equilibrium and Kc when the concentration of one species in the reaction mixture has been increased?
The position of equilibrium shifts up to use up the added substance, shifts to the side that the added chemical is not on, no change in Kc.
What happens to equilibrium and Kc when a catalyst has been introduced?
No change, the rate of the forward and reverse reactions increase equally, the activation energy for forward and reverse reactions are lowered equally, no change in Kc.
What is the expression for the reaction quotient for the reaction:
N2 (g) + 3H2 (g) 2NH3 (g)
It is exactly the same as that for Kc except that the concentrations are not equilibrium concentrations: Q = (NH3)^2/(N2)(H2)^3
What happens when the reaction quotient is bigger than the equilibrium constant?
When Q > Kc the system is not at equilibrium so the reaction must proceed to the left towards equilibrium the concetrations of the products on the right of the equation and the top of the expression for Q are too high and so the products must be used up to reduce the vale of Q until it equals Kc and the system is at equilibrium.
What happens when the reaction quotient is smaller than the equilibrium constant?
When Q < Kc the system is not at equilibrium so the reaction may proceed tot he right towards equilibrium so more products must be produced.
What happens when the reaction quotient is equal to the equilibrium constant?
The system is at equilibrium.
