Equilibrium - Topic 7

I really didn't give a Chatalier about this unit.

What is a state of equilibrium?

What is a state of equilibrium?

When the rates of forward and reverse reaction are equal in a closed system

What is the equilibrium law?

The formula that determines the equilibrium constant for a reaction

What is the equilibrium constant?

K∨c

What does the equilibrium constant indicate?

Its magnitude indicates the extent of a reaction at equilibrium and its temperature dependence

What is a catalyst?

A substance that has no impact on the equilibrium position of a reaction or the equilibrium constant

What is the reaction quotient?

The reaction quotient, Q, measures the relative amount of products and reactants at a point of time during a reaction

How is Q related to Kc?

Q is the equilibrium constant’s expression with non-equilibrium concentrations

What can change the position of equilibrium?

Temperature, concentration, and pressure

What is the state of equilibrium?

When in a reaction, both the forwards and reverse reactions are occurring simultaneously, with both products and reactants being constantly interconverted

What are some examples of equilibrium in everyday life?

Water cycle, condensation in hot pots, sealed bottles of carbonated beverages

What is dynamic equilibrium?

When equilibrium has been reached such that interconversion no longer results in a net change of either products or reactants

What is the key symbol that differentiates equilibria reactions from others?

⇌ rather than →

What happens to in a heterogenous solution if excess solid is present?

The solid will begin to dissolve, meaning that the rate of dissolution and precipitation are not equal, however once the solid has been dissolved as much as possible, the dissolution and precipitation rates become equal, resulting in a dynamic equilibrium

What is one example of a dynamic equilibrium?

When sodium chloride is dissolved in water

On what do the relative rates of forwards and reverse reactions depend?

The physical conditions, chemical conditions, and the existence of a catalyst

What is the difference between a homogenous equilibrium and a heterogenous equilibrium?

In a homogenous equilibrium, all substances are in the same state, and in a heterogenous equilibrium, substances are in differing states

What is the position of equilibrium?

Whether the reactants or products are favoured

What is the law of chemical equilibrium?

That at a given temperature, the ratio of the concentration of products to the concentration of reactants is a constant

What does the “c” mean in the equilibrium constant, Kc?

This represents that the constant is calculated using the concentration values of substances in the reaction

What direction does each magnitude of Kc mean?

If Kc is big, the forwards reaction is favoured at the temperature and if Kc is small, the reverse reaction is favoured and the specific reaction is unfavourable at the given temperature

How does Kc change if a reaction is reversed?

It is now 1/Kc

How does Kc change if a reaction’s coefficients are halved?

It is now √Kc

How does Kc change if a reaction’s coefficients are doubled?

It is now Kc²

How does Kc change if a reaction is summed?

It is now Kc₁ + Kc₂ and so on

What does increasing the concentration of a reactant do to the equilibrium position?

It makes it favour the forwards reaction

What does increasing the concentration of a products do to the equilibrium position?

It makes it favour the reverse reaction

Why does concentration of water impact the reaction without changing its concentration overall?

Water is a pure substance, therefore its concentration and volume will increase proportionally, making there no change in the concentration overall. Despite this, the reaction is still impacted because the concentration of any aqueous identities will be changed

How does increasing the temperature of a system change the equilibrium position?

The endothermic reaction would be favoured, which can then determine whether the forwards or reverse reaction would be favoured

How does decreasing the temperature of a system change the equilibrium position?

The exothermic reaction would be favoured, which can then determine whether the forwards or reverse reaction would be favoured

What is a disturbance ONLY impacts gases?

A change in volume or pressure

Why does the specific change in volume or pressure not matter?

Because the two are inversely proportional, as detailed by Boyle’s law

How does the equilibrium position change if the volume of a container is decreased (increase in pressure)?

The reaction will favour the side with the lesser stoichiometric mole ratio

How does the equilibrium position change if the volume of a container is increased (decrease in pressure)?

The reaction will favour the side with the greater stoichiometric mole ratio

What is Le Châtalier’s Principle?

If a change is made to a system that is in equilibrium, the balance between the forward and reverse reactions will shift to offset this change and return the system to equilibrium

How is cause and effect used by scientists?

Cause and effect is used to describe an event that is resulting from another previous event, which is often used to develop hypotheses (if, then, because). This could connect to Le Châlalier’s Principle as it details the result of a change on a system, however the concepts do not directly connect because the changes are not always set in stone

What is the Haber Process?

The Haber process is a synthesis of ammonia from its elements developed by Fritz Haber, a German chemist

What is the Haber process used for?

The process helps produce fertilizers that are difficult to naturally find due to large populations and has single handedly ensured that agriculture is advanced enough to support the ever growing population

What is the chemical reaction for the Haber process?

N₂(g) + 3H₂(g) ⇌ 2NH₃(g)

Why is Fritz Haber often brought up to illustrate the ethical concerns of scientific discoveries?

Fritz Haber was responsible for saving an incomprehensibly large amount of people due to his advances in agriculture, however he is also known for being the “father of chemical warfare”. During WWI, he worked with the German Army to create poisonous gases that could be used against their enemies. Therefore, he was responsible for both saving and killing many thousands of people. Were his advances good or bad? Do they cancel each other out?

What does it mean if Q is greater than Kc?

The concentration of products is higher than at equilibrium. The reverse reaction will be favoured until equilibrium is reached

What does if mean if Q is lesser than Kc?

The concentration of reactants is higher than at equilibrium. The forwards reaction will be favoured until equilibrium is reached

What does each letter stand for in an ICE table?

I → Initial

C → Concentration

E → Equilibrium