Equilibrium

What does it mean when a reaction is at equilibrium

• WHAT

• WHAT

What does it mean when a reaction is at equilibrium

• Forward and reverse reactions occur at the same time (rates are equal)

• [products] and [reactants] remain constant (steady state)

What is the equilibrium constant

K (upercase)

For K

• WHAT 

• Follows WHAT 

• Describes the effects of the “WHAT” of reaction 

1. WHAT 

2. WHAT 

For K

• Ration of products to reactants  

• Follows reaction stoichiometry  

• Describes the effects of the “thermodynamic conditions” of reaction 

1. Temperature specific  

2. Reaction specific  

What is the general reaction for the equilibrium constant

K = [products]^x / [reactants]^n (if nR →← xP)

What is Kc (concentration- in mol/L) given the reaction aA + bB →← cC + dD

Gases or aqueous

Kc = [C]^c [D]^d / [A]^a [B]^b 

What is Kp (pressure - in bar) given the reaction aA + bB →← cC + dD

Gases 

Kc = PC^c PD^d / PA^a PB^b 

K is never in WHAT

Pure liquids or pure solids

What is the reaction between Kc and Kp

Kp = Kc (RT)^Δn

where 

R = 0.008314 barL/molK

T = Kalvin 

Δn = nProducts (gas) - nReactants (gas) 

What are the units for K 

Unitless

the larger the value of K the further a reaction has gone in the WHAT direction

the larger the value of K the further a reaction has gone in the FORWARD direction

The equilibrium constant can be used to determine whether the formation of WHAT or WHAT is favoured

The equilibrium constant can be used to determine whether the formation of REACTANTS or PRODUCTS is favoured

Reactions must be occurring at the same WHAT for their WHAT to be compared to each other

Reactions must be occurring at the same TEMPERATURE for their EQUILIBRIUMS to be compared to each other

if K > 1 WHAT is favoured

WHAT does the graph look like 

if K > 1 PRODUCTS is favoured

WHAT does the graph look like 

if K < 1 WHAT is favoured

WHAT does the graph look like 

if K < 1 REACTANTS is favoured

WHAT does the graph look like 

If K1 = [NO] / [N2O2] and reaction 2 reverses the reaction what happens to K1

1 / K1

If K1 = [NO] / [N2O2] and reaction 3 multiplies the reaction by 2 what happens to K1

To the power of the multiple ex: 2 in this instant so (K1)²

Reaction quotient, Q:

• The same form as the WHAT 

• Measured at WHAT during the reaction 

Reaction quotient, Q:

• The same form as the EQUILIBRIUM CONSTANT 

• Measured at ANYTIME during the reaction 

If Q < K, reaction is in the WHAT

Forward direction

If Q = K reaction is WHAT

at equilibrium

If Q > K reaction is in the WHAT direction

Reverse direction

K depends on WHAT between the forward and reverse reactions

Final concentration

What are the steps to determining which direction a reaction will proceed

1. Calculate Q

2. Compare Q to K

Le Chatelier’s Principle states that when a system at equilibrium is perturbed, the system will establish a WHAT to WHAT the disturbance

Le Chatelier’s Principle states that when a system at equilibrium is perturbed, the system will establish a NEW EQUILIBRIUM to COUNTERACT the disturbance