Equilibrium Flashcards
What is dynamic equilibrium?
An equilibrium in which the rates of forward and reverse processes are equal.
What is chemical equilibrium?
Chemical equilibrium is when the concentrations of all the reactants and products of a chemical reaction remain constant over time.
Are all chemical equilibria dynamic equilibria?
Yes
What is the equilibrium position?
The relative concentration of reactants and products in a chemical reaction system at equilibrium.
What are reversible reactions?
Chemical reactions that proceed in both the forward and reverse directions.
In which direction can equilibrium be reached?
An equilibrium position can be reached starting from the forward or reverse reaction.
Is the equilibrium position the same starting from either side?
Yes
What does ICE in i.c.e. Table stand for?
Initial concentrations, change in concentrations and equilibrium concentrations
What is equilibrium law?
The mathematical description of a chemical system at equilibrium.
What states are used in equilibrium law?
Gaseous and aqueous states only
What is K?
K is the equilibrium constant, a numerical value that defines equilibrium law for a given system.
Is K reported with units?
No
Will the equilibrium constant always have the same value regardless of initial concentrations provided that all other variables are kept the same?
Yes
Does K depend on temperature?
Yes
If K represents the forward reaction, what does K’ (K prime) represent?
The reverse reaction. K’ = 1/K
What is homogeneous equilibrium?
Chemical equilibrium in which all reactants and products are in the same state of matter.
What is heterogeneous equilibrium?
When reactants and products are present in more than one state.
Does the equilibrium position of heterogeneous equilibrium depend on the quantities of pure solids and liquids?
No, because the concentrations of pure solids and liquids do not change.
Do solids and liquids appear in the equilibrium law equation?
No
How can equilibrium positions be disturbed?
Through changes in pressure, temperature, concentration or a combination of these.
What is Le Châtelier’s Principle?
When a chemical system at equilibrium is disturbed by a change in a property, the system adjusts in a way that opposes the change.
What is an equilibrium shift?
An adjustment by a system at equilibrium that results in a change in the concentrations of reactants and products.
What happens when K is far less than one?
The equilibrium shifts far to the right favouring products
What happens when K is about equal to one?
The concentration of products is about equal to that of reactants
What happens when K is much higher than 1?
The equilibrium shifts far to the left favouring reactants.
What happens when a reactant is added to a reaction?
The equilibrium shifts to the right, favouring products to oppose the change. (More product needs to be created)
What happens when some reactant is removed from a reaction?
The equilibrium shifts to the left (towards reactants) to oppose the change and produce more of the reactant
What happens when the concentration of a reactant increases in a reaction?
The equilibrium shifts to the right because the number of successful collisions for the forward reaction increases (and vice versa)
What happens when the concentration of products increases?
The equilibrium shifts to the left to create more reactants causing the reverse reaction rate to increase.
In an endothermic reaction, when would the equilibrium shift left?
When the reaction is cooled (thermal energy removed). (It is like having a reactant removed) therefore reaction shifts left.
In an endothermic reaction, when would equilibrium shift right?
If thermal energy is added.
In an exothermic reaction, when would equilibrium shift right?
If thermal energy is removed (energy is a product), the equilibrium will shift right
In an exothermic reaction, when will equilibrium shift left?
If thermal energy is added (since energy is a product, this will be like having too much product)
When do pressure and volume have no effect on gases?
When there are the same number of moles on both sides.
What happens in a gaseous reaction when volume decreases and pressure increases?
The equilibrium shifts to the side with less moles. (Vice versa is also correct).
Do catalysts change equilibrium position?
No. But they help the reaction reach equilibrium much faster.
What are inert gases?
Non-reactive gases (Noble gases).
What are inert gases good for?
Increasing pressure causing more collisions.
Does K change with concentration?
No
What happens when Q is less than K?
Equilibrium shifts to the right till equilibrium is reached.
What happens when Q is equal to K?
The reaction is at equilibrium. No shift.
What happens when Q is greater than K?
Equilibrium shifts to the left until equilibrium is reached.
Explain the Hundo Rule.
If the concentration to which x is added or subtracted is at least 100x greater than the value of K, then the simplifying assumption will give an error of less than 5% therefore valid.
What is Ksp?
Ksp is K for a saturated solution.
Is temperature always included when reporting Ksp?
Yes.
What happens when Q is greater than Ksp?
Equilibrium shifts left; precipitate forms until solution reaches new equilibrium.
What happens when Q is less than Ksp?
Equilibrium shifts right. No precipitate since solution is unsaturated.
What happens when Q is equal to Ksp?
Solution is at equilibrium.
What is called the common ion effect?
Lowering the solubility of an ionic compound by the addition of a common ion.
