equilibria + Kp (y2) Flashcards
(29 cards)
What is dynamic equilibrium?
The forward and reverse reactions occur at the same rate in a closed system; concentrations of reactants and products remain constant.
What are the conditions for equilibrium?
A closed system and a reversible reaction.
What does it mean if equilibrium lies to the left?
More reactants than products are present at equilibrium.
What does it mean if equilibrium lies to the right?
More products than reactants are present at equilibrium.
State Le Chatelier’s Principle.
If a change is made to a system at equilibrium, the position of equilibrium will shift to counteract the change and reestablish a new equilibrium
What effect does increasing temperature have on equilibrium?
It shifts in the endothermic direction.
What effect does decreasing temperature have on equilibrium?
It shifts in the exothermic direction.
What effect does increasing pressure have on equilibrium?
It shifts to the side with fewer gas molecules.
What effect does decreasing pressure have on equilibrium?
It shifts to the side with more gas molecules.
What effect does adding a catalyst have on equilibrium?
It does not affect the position; it increases the rate of both forward and reverse reactions equally.
What is the general formula for Kc?
Kc = [products]^coefficients / [reactants]^coefficients (square brackets denote concentration in mol/dm³).
What are the units of Kc?
Units vary depending on reaction; use mol/dm³ and cancel powers accordingly.
What does a large Kc value (»1) indicate?
Equilibrium lies to the right (more products).
What does a small Kc value («1) indicate?
Equilibrium lies to the left (more reactants).
How do you calculate equilibrium concentrations from Kc?
Use an RICE table
then do conc= mol/ vol
What is Kp used for?
Equilibria involving gases using partial pressures instead of concentrations.
How do you calculate partial pressure?
Partial pressure = mole fraction × total pressure; mole fraction = moles of gas / total moles of all gases.
What is the general expression for Kp?
Kp = (P products)^coefficients / (P reactants)^coefficients (round brackets denote partial pressures).
What are the units of Kp?
Depend on number of gas molecules; use atm or Pa and cancel powers accordingly.
How does temperature affect Kp?
For exothermic reactions
Does pressure change affect Kp?
No
What are the steps to calculate Kc from concentration data?
Write balanced equation → Use RICE table → Calculate equilibrium concentrations → Substitute into Kc → Calculate value and units.
What are the steps to calculate Kp from partial pressures?
Calculate mole fractions → Find partial pressures → Substitute into Kp → Cancel units if needed.
