General Chemistry Ch 6. Equilibrium Flashcards
Reversible reactions
Steady state in which energy is minimized in entropy is maximized, dynamic
Dynamic
Reactions are still occurring, just at a constant rate
Law of mass action
Gives the expression for the equilibrium constant, Keq
Chemical equilibria
Dynamic, concentrations of reactants and products remain constant because the rate of the forward reaction equals the rate of the reverse reaction
Law of mass action
Gives the expression for the equilibrium constant Keq, if a system is at equilibrium at a constant temperature, then…
Key = [C]^c*[D]^d/[A]^a/[B]^b
Does not include pure solids and liquids, only gases and aqueous species
Reaction quotient
Q - Same form as keq but can be calculated at any concentrations at any given time during a reaction, relates the reactant and product concentrations at any given time during a reaction
Equilibrium constant
Keq - ratio of products to reactants at equilibrium with each species raised to its stoichiometric coefficients, constant at a constant temperature
Q
DeltaG<0 and the reaction proceeds in the forward direction
Q=Keq
DeltaG=0 and the reaction is in dynamic equilibrium
Q>Keq
DeltaG>0 and the reaction proceeds in the reverse direction
Keq>1
The products are present in greater concentrations at equilibrium
Keq=1
Products and reactants are both present at equilibrium at reasonably similar levels
Keq<1
The reactants are present in greater concentration at equilibrium
Keq«<1
The amount of reactants that have been converted to products can be considered negligible in comparison to the initial concentration of reactants
Le Chateliers principle
States that when a chemical system experiences a stress, it will react so as to restore equilibrium
Types of stresses applied to a system
Changes in concentration, pressure and volume, and temperature
Changing concentration Le Chateliers
Increasing the concentration of reactants or decreasing the concentration of products will shift the reaction to the right, increasing the concentration of products or decreasing the concentration of reactants will shift the reaction to the left
Changing pressure/volume Le Chateliers
Increasing pressure on a gaseous system (decreasing volume) will shift the reaction toward the side with fewer moles of gas, decreasing pressure (increasing volume) will shift the reaction toward the side with more moles of gas
Changing temperature Le Chateliers
Increasing the temperature of an endothermic reaction or decreasing the temperature of a exothermic reaction will shift the reaction to the right, decreasing the temperature of an endothermic reaction or increasing the temperature of an exothermic reaction will shift the reaction to the left
Kinetic products
Higher in free energy than thermodynamic products and can form at lower temperature, sometimes termed “fast” products because they can form more quickly under such conditions
Thermodynamic products
Lower in free energy than kinetic products and are therefore more stable, despite proceeding more slowly than the kinetic pathway, the thermodynamic pathway is more spontaneous (more negative deltaG)
