Writing & Understanding K
This equilibrium expression is written for: 2SO2(g) +O2(g) <-> 2SO3(g)
What is K=[SO3]^2 / [SO2]^2[O2]
If Q<K, the reaction will shift in this direction.
What is toward products (right)?
This table format is used to organize equilibrium concentration problems.
RICE table
Adding more reactant to a system at equilibrium causes the system to shift in this direction.
What is toward products (right)?
At equilibrium, the forward and reverse reaction rates are this relative to each other.
What is equal?
Pure solids and liquids are omitted from this expression because their values are constant.
What is the equilibrium constant expression (K)?
If Q>K, the reaction will shift in this direction.
What is toward reactants (left)?
In an RICE table, reactant changes are written with this sign.
What is negative (−x)?
Decreasing the volume of a gaseous system shifts equilibrium toward the side with this.
What is fewer moles of gas?
Even though particles continue reacting, concentrations remain constant because equilibrium is this type of process.
What is dynamic equilibrium?
If a reaction is reversed, this happens to the value of K.
What is it becomes the reciprocal (1/K)?
This value relationship means the system is already at equilibrium
Q=K
For the reaction
N2(g)+3H2(g)⇌2NH3(g),
if x moles of NH3 form, the change in H2 is written as this in the ICE table.
What is −3x?
Changing the concentration of a species changes this value but not the equilibrium constant.
What is Q (reaction quotient)?
A particulate diagram showing many more products than reactants would correspond to this type of K value.
K>>1
If all coefficients are doubled, this happens to K.
What is K is squared?
For K=5.0×10^−4 Q=0.80, the system will shift this way.
What is left (toward reactants)?
Before using concentrations in a Kc expression, quantities given in grams must first be converted to this unit.
What is molarity (mol/L)?
Changing temperature affects this value because heat acts like a reactant or product.
What is the equilibrium constant (K)?
A graph of concentration vs. time becomes flat at equilibrium because this quantity is no longer changing.
What is concentration (no net change)?
This value of K indicates products are strongly favored at equilibrium.
What is K≫1 (much greater than 1)?
This must be calculated first when only initial concentrations are given and you must predict direction.
What is the reaction quotient (Q)?
For the reaction
H2(g)+I2(g)⇌2HI(g)
A 1.00 L container initially contains:
[H2]=0.50 M
[I2]=0.50 M
[HI]=0.10 M
At this temperature, Kc=4.0
Calculate the equilibrium concentration of HI.
What is 0.80 M?
For an exothermic reaction, increasing temperature shifts equilibrium in this direction and changes K in this way.
What is left (toward reactants) and K decreases?
Two containers have different numbers of particles but the same reactant-to-product ratio. They will have this same value.
What is the same equilibrium constant (K)?