Equilibrium Flashcards
What is equal at equilibrium?
Rate of forward and rate of reverse reactions
What chemicals can be included in an equilibrium constant expression?
Gases and aqueous
NO SOLIDS OR LIQUIDS
When writing a K or Q expression in terms of concentrations, you must use
Brackets
Ex. [A]
When writing a K or Q expression in terms of pressures, you must use
partial pressures
Ex. PA
If K > 1, then the _________ are favored at equilibrium.
Products
If 0 < K < 1, then the _________ are favored at equilibrium.
Reactants
When K is a large number (usually greater than 1000), we can treat the reaction as if it is
going to completion and using up the limiting reactant.
When K is a very small number (usually less than 0.0001), we can assume that
a negligible amount of reactants are used.
Note: You CANNOT assume that no products are formed. Even if it is a tiny amount of reactants, it’s still significantly greater than 0.
An example of this is when Ka is used in weak acid equilibrium.
When you reverse a reaction, what do you do to K?
1/K
When you triple the coefficients of a reaction, what do you do to K?
K3
When you add two reactions together, what do you do to their Ks?
Multiply them together
If Q < K, then the reaction is proceeding to produce more _________.
Products
If Q > K, then the reaction is proceeding to produce more _________.
Reactants
If Q < K, then the forward reaction is _______ than the reverse reaction.
Faster
If Q > K, then the forward reaction is _______ than the reverse reaction.
Slower
Effect of catalysts on equilibrium
Does not disturb equilibrium or cause shifting of reaction
Effect of adding inert (unreacting) gas on equilibrium
Does not disturb equilibrium or cause shifting of reaction
Effect of adding a solid on equilibrium (not dissolving to be aqueous)
Does not disturb equilibrium or cause shifting of reaction
Decreasing the volume of gases at equilibrium will cause the reaction to shift to the side of the reaction
that has less moles of gas to decrease pressure back down.
Note: If equal number of moles of gas on each side, equilibrium will not be disturbed.
How T and K are related for endothermic rxns
Increasing T causes K to increase
How T and K are related for exothermic rxns
Increasing T causes K to decrease
What is the only way that K changes?
Changing temperature
When adding water to dilute an aqueous-phase reaction, the reaction will shift to the side
with more moles of aqueous chemicals
Adding a common ion to a solution at equilibrium will cause the reaction to shift _______________ the side with the common ion.
Away from
Ksp for insoluble compound made of 2 ions
Ksp = s2
Ksp for insoluble compound made of 3 ions
Ksp = 4s3
s is defined as the molar solubility (how much solid dissolves) of a solid with units of
mol/L OR M
The larger the value of s for an insoluble solid, the ________ soluble the solid is.
more
When comparing two solids made up of an equal number of ions, the solid with a ________ Ksp is more soluble.
Greater
If Qsp is ______ than Ksp, a precipitate will form
Greater
