General Chemistry II Exam 2 Study Guide –
Chemical Equilibrium, Le Châtelier’s Principle
& Acids|Verified Questions Complete with A+
Graded Rationales Latest Updated 2026
Dynamic Equilibrium
For a chemical reaction, the condition in which the rate of the forward reaction equals the
rate of the reverse reaction.
Equilibrium Constant (K)
The ratio (at equilibrium) of the concentrations of the products raised to their stoichiometric
coefficients divided by the concentrations of the reactants raised to their stoichiometric
coefficients.
aA+bB↔cC+dD
K=([C]^c[D]^d)/([A]^a[B]^b)=[products]/[reactants]
Relative Size of Keq
If K>>1, reaction proceeds forward; favors products
If K<<1, reaction proceeds a little; favors reactants
If K≈1, reaction proceeds about half way
Relationships Between Keq and the Chemical Equation
If the reaction is reversed: Kreverse = 1/Kforward
If the coefficients in the equation are multiplied by a factor: raise the equilibrium constant to
the same factor
If two or more individual chemical equations are added: multiply the corresponding
equilibrium constants by each other to obtain the overall Keq
Heterogeneous Equilibria Involving Solids and Liquids
The concentrations of pure liquids and solids remain constant and are therefore excluded
from the equilibrium expression.
Expressing Keq in Terms of Pressure
, Kp=Kc(RT)^(∆n)
where Kp is the equilibrium constant with respect to partial pressures in atm, Kc is the
equilibrium constant with respect to concentration, R=0.08206 L·atm/mol·K, T is temperature
in K, and ∆n is the change in number of moles of gas
Reaction Quotient (Qc)
the ratio (at any point in the reaction) of the concentrations of the products raised to their
stoichiometric coefficients divided by the concentrations of the reactants raised to their
stoichiometric coefficients.
Q, K, and the Direction of a Reaction
If Q<K, reaction goes forward (toward products)
If Q=K, reaction is at equilibrium
If Q>K, reaction goes backwards (toward reactants)
Le Châtelier's Principle
When a chemical system at equilibrium is disturbed, the system shifts in a direction that
minimizes the disturbance.
Summary of Le Châtelier's Principle: Changes in Pressure
Decreasing the volume causes the reaction to shift in the direction that has the fewer moles
of gas particles.
Increasing the volume cases the reaction to shift in the direction that has the greater number
of moles of gas particles.
If a reaction has an equal number of moles of both sides of the chemical equation, then a
change in volume produces no effect on the equilibrium.
Adding an inert gas to the mixture at a fixed volume has no effect on the equilibrium.
Summary of Le Châtelier's Principle: Changes in Concentration
Increasing the concentration of one or more of the reactants (which makes Q<K) causes the
reaction to shift in the direction of the products.
Increasing the concentration of one or more of the products (which makes Q>K) causes the
reaction to shift in the direction of the reactants.
Decreasing the concentration of one or more of the reactants (which makes Q>K) causes the
reaction to shift in the direction of the reactants.
Decreasing the concentration of one or more of the products (which makes Q<K) causes the
reaction to shift in the direction of the products.
Summary of Le Châtelier's Principle: Changes in Temperature
Chemical Equilibrium, Le Châtelier’s Principle
& Acids|Verified Questions Complete with A+
Graded Rationales Latest Updated 2026
Dynamic Equilibrium
For a chemical reaction, the condition in which the rate of the forward reaction equals the
rate of the reverse reaction.
Equilibrium Constant (K)
The ratio (at equilibrium) of the concentrations of the products raised to their stoichiometric
coefficients divided by the concentrations of the reactants raised to their stoichiometric
coefficients.
aA+bB↔cC+dD
K=([C]^c[D]^d)/([A]^a[B]^b)=[products]/[reactants]
Relative Size of Keq
If K>>1, reaction proceeds forward; favors products
If K<<1, reaction proceeds a little; favors reactants
If K≈1, reaction proceeds about half way
Relationships Between Keq and the Chemical Equation
If the reaction is reversed: Kreverse = 1/Kforward
If the coefficients in the equation are multiplied by a factor: raise the equilibrium constant to
the same factor
If two or more individual chemical equations are added: multiply the corresponding
equilibrium constants by each other to obtain the overall Keq
Heterogeneous Equilibria Involving Solids and Liquids
The concentrations of pure liquids and solids remain constant and are therefore excluded
from the equilibrium expression.
Expressing Keq in Terms of Pressure
, Kp=Kc(RT)^(∆n)
where Kp is the equilibrium constant with respect to partial pressures in atm, Kc is the
equilibrium constant with respect to concentration, R=0.08206 L·atm/mol·K, T is temperature
in K, and ∆n is the change in number of moles of gas
Reaction Quotient (Qc)
the ratio (at any point in the reaction) of the concentrations of the products raised to their
stoichiometric coefficients divided by the concentrations of the reactants raised to their
stoichiometric coefficients.
Q, K, and the Direction of a Reaction
If Q<K, reaction goes forward (toward products)
If Q=K, reaction is at equilibrium
If Q>K, reaction goes backwards (toward reactants)
Le Châtelier's Principle
When a chemical system at equilibrium is disturbed, the system shifts in a direction that
minimizes the disturbance.
Summary of Le Châtelier's Principle: Changes in Pressure
Decreasing the volume causes the reaction to shift in the direction that has the fewer moles
of gas particles.
Increasing the volume cases the reaction to shift in the direction that has the greater number
of moles of gas particles.
If a reaction has an equal number of moles of both sides of the chemical equation, then a
change in volume produces no effect on the equilibrium.
Adding an inert gas to the mixture at a fixed volume has no effect on the equilibrium.
Summary of Le Châtelier's Principle: Changes in Concentration
Increasing the concentration of one or more of the reactants (which makes Q<K) causes the
reaction to shift in the direction of the products.
Increasing the concentration of one or more of the products (which makes Q>K) causes the
reaction to shift in the direction of the reactants.
Decreasing the concentration of one or more of the reactants (which makes Q>K) causes the
reaction to shift in the direction of the reactants.
Decreasing the concentration of one or more of the products (which makes Q<K) causes the
reaction to shift in the direction of the products.
Summary of Le Châtelier's Principle: Changes in Temperature
