Unit 4 Equilibria Flashcards
What is ‘dynamic equilibria’?
Where the forward and backward reactions at same rate, concentrations of reactants and products stay constant.
What is the equilibrium constant equation if 3A + 2B ->/<- 4C + D?
Kc = [C]4 [D] / [A]3 [B]2
What is Le Chatelier’s Principle?
The equilibrium will respond to counteract any imposed change.
(in exam questions mention equilibrium, the direction of equilibrium shift and the effect of shift).
In an exothermic reaction a low temperature will shift the equilibrium in which direction?
To the right to increase the energy and so increases the yield.
In an endothermic reaction a high temperature will shift the equilibrium in which direction?
To the right to lower the energy which also increases yield and means faster rate.
What are the disadvantages of using high pressures for gases?
Expensive and can lead to a higher risk of explosion.
An increase in pressure will shift the equilibrium in which direction?
The increase in pressure would shift the equilibrium to the side with fewest number of moles to decrease the pressure.
What is the relationship between pressure and volume?
Inversely proportional. If volume is decreased, pressure is increased and vice versa.
What effect does concentration have on equilibrium?
The equilibrium moves to the side to increase or decrease the imposed change. So if the concentration of a reactant is increased the only way its concentration can be reduced is by it reacting with the other reactant(s) producing more products hence the equilibrium has moved to the right.
What effect does a catalyst have on the equilibrium?
No effect on equilibrium because the rate of forward and rate of backward reactions increase by the same amount.
For the reaction: aA + bB + cC + dD what is the Kc constant?
[C] to the power c * [D] to the power dDivided by[A] to the power a * [B] to the power b
What are the units for this equation?2A + B –> C + 2D
There are no units as they cancel
Which way does the position if equilibrium shift if Kc < 1?
To the left.
If Kc > 1, which way does the position of equilibrium shift?
To the right.
If Kc = 1, where does the position of equilibrium lie?
Halfway between reactants and products.
