Equilibrium

Question 1

What can be changed in a reaction to alter the equilibrium position?

Answer 1

Concentration, temperature, pressure/volume (only applies to gases)

Question 2

What is meant by an “open system”?

Answer 2

An open system allows matter and energy to be exchanged with the surroundings

Question 3

What happens to the equilibrium position when the product concentration is increased?

Answer 3

The reverse reaction increases and equilibrium moves to the left

Question 4

Are all reactions reversible?

Answer 4

No, for example due to the formation of energetically stable products or loss of products into the environment

Question 5

What does Le Chatelier’s principle state?

Answer 5

If an equilibrium system is subjected to a change, the system will adjust itself to partially oppose the effect of the change

Question 6

What is a “closed system”?

Answer 6

A reaction vessel that does not allow the reactant or product particles to escape

Question 7

What happens to the equilibrium position when the reactant concentration is increased?

Answer 7

The forward reaction increases and equilibrium moves to the right

Question 7

Give an example of an “open” system.

Answer 7

A flask with no lid that allows heat and gas products escape

Question 8

On an equilibrium graph how do you know the reaction has reached equilibrium?

Answer 8

When equilibrium is
established the
concentration lines are
horizontal

Question 9

What type of system is it when energy can escape but not matter?

Answer 9

Closed system

Question 10

What is meant by the term “reversible reaction”?

Answer 10

Reactions in which the conversion of reactants to products and products to reactants occur simultaneously.

Question 11

What can you measure using observation in equilibrium reactions?

Answer 11

You can observe whether the forward or reverse reaction has occurred if the reactants and products have different colours

Question 12

Are physical changes reversible?

Answer 12

Generally they are reversible as chemical bonds remain unchanged

Question 13

In a reaction where a gas is produced what type of system is required for equilibrium to be reached?

Answer 13

A closed system

Question 14

Why is a substance in a system more likely to react when the temperature is higher?

Answer 14

The particles of that substance have more kinetic energy, causing them to collide more often with the other particles in the system, making the reaction occur

Question 15

What does Kc represent?

Answer 15

The equilibrium constant

Question 16

How are equilibrium reactions symbolised?

Answer 16

Equilibrium reactions are symbolised by ⇌

Question 17

When is a state of dynamic equilibrium reached?

Answer 17

A state of equilibrium is reached when the rate of the forward and reverse reactions are equal

Question 18

What is activation energy?

Answer 18

The minimum amount of energy required in the collision between reactants for a reaction to occur

Question 19

How can you measure
the concentration of
an equilibrium using
pH?

Answer 19

You can measure the change in pH and calculate the H3O+ concentration, then use simple stoichiometry

Question 19

Can forward and reverse reactions occur at the same time?

Answer 19

Yes, a forward and reverse reaction can occur at the same time if the reaction occurs within a closed system

Question 20

Is the equilibrium constant value largest when the concentration of reactants is larger than the products?

Answer 20

No

Question 21

What is the impact on the equilibrium position when a catalyst is added to a reaction in a closed system?

Answer 21

There is no impact on the equilibrium position. Equilibrium will only be reached faster

Question 22

What concentrations are not included when calculating the equilibrium constant?

Answer 22

Concentrations of pure liquids and solids are not included, water is only included if it is a product such as in condensation reactions

Question 23

What energy is required to remove an electron from an element?

Answer 23

First ionisation energy

Question 24

“True or False? The stronger the electronegativity, the more readily the element will accept electrons.”

Answer 24

True

Question 25

Where can the elements with the lowest ionisation energy be found on the periodic table?

Answer 25

“Bottom left e.g. Cs, Rb, Ba”

Question 26

If Kc is larger than 104 is there significantly more reactant or product?

Answer 26

Product

Question 27

What kind of ionisation energy makes elements lose electrons more readily?

Answer 27

Low ionisation energy

Question 28

“True or false? Is the
Kc of a reaction
temperature
dependent?”

Answer 28

True

Question 29

What does RICE stand for?

Answer 29

Reaction, initial concentration, change in concentration, equilibrium concentration

Question 30

What happens to the equilibrium position for an endothermic reaction when heat is added?

Answer 30

The equilibrium position will move towards the product side as heat is stored in the molecule

Question 31

What can you do to increase the concentration of gas in a closed system?

Answer 31

Decrease the volume