Topic 10 + 11: Equilibrium I, II Flashcards
What is dynamic equilibrium
A reversible reaction in a closed system where the rates of the forwards and backwards reaciton are equal and so the concentrations of reactants and products do not change.
What is the affect of increasing the temperature on a reversible reaction?
The forward reaction is exothermic
The rate of reaction will increase because more reactants will have sufficient energy to reaction (more than or equal to Ea)
The position of equilibrium will shift to the left (the endothermic direction) in order to decrease the temperature of the system, thereby countering the change, according to Le Chatelier’s Principle
What is the affect of increasing the concentration of products on a reversible reaction?
The position of equilibrium will shift to the left to decrease the concentration of the products, countering the change due to Le Chatelier’s Principle.
What is the affect of increasing the pressure of a reaction:
2A(g) + B(g) < -> C(g) + D(s)
Rate of reaction increases because of increased pressure.
More moles of gas on the reactant side. Position of equilibrium will shift to the right to decrease the moles of gas and therefore decrease the pressure, countering the change due to Le Chatelier’s Principle.
What is the affect of adding a catalyst to the position of equilibirum.
No change.
Increases the rate at which equilibrium is reached because catalysts increase the rate of reaction of the forwards and backwards reactions equally.
What is Kc for the reaction:
aA + bB < = > cC + dD
Kc = ([C]^c x [D]^d) / ([A]^a x [B]^b)
What is the only change in condition to affect the value for Kc
temperature
what happens if you have a solid in the equation you need to find Kc for
IGNORE solids entirely
What is the Kp expression written in terms of
partial pressures
What is Kp for the reaction
aA + bB < => cC + dD
all of the state symbols are gases
Kp = [p(C)^c x p(D)^d] / [p(A)^a x p(B)^b]
where p(A) indicates the partial pressure of A at eqm
What happens in heterogeneous reactions for Kp
Solids and liquids are ignored
What changes the value for Kp
Change in temperature
How do you calculate the partial pressures from the number of moles and total pressure
- The number of moles of each gas should be used to first calculate the mole fractions (mole of each gas/ total number of moles)
- The mole fractions are then multiplied by the total pressure to get the partial pressures
For an endothermic reaction; what happnes to K(p/c) if the temperature increases?
Increases
Why does the value of the equilibrium constant increase with increasing temperature for an endothermic reaction?
Increase temperature shifts position of equilibrium to the product side so the equilibrium concentrations (or partial pressures) of the products are larger and the reactants smaller so that the temperature is decreased (in accordance with Le Chatelier’s principle)
