5.1 Static & Dynamic Equilibrium

Question 1

What are the factors affecting the rates of reaction?

Answer 1

Temperature, concentration (for solutions), pressure (for gases), surface area (solid reactants), use of catalysts

Question 2

Definition of collision theory

Answer 2

1) Particles have to collide at the correct orientation
2) Sufficient activation energy (for particles to collide and break bonds)

Question 3

What is a dynamic equilibrium?

Answer 3

• When the rate of forward and reverse reactions are equal.
• Concentration of reactant & products remain constant, but the reaction does not go to completion as they continue reacting on an atomic/microscopic level

Question 4

Name the 5 properties of a dynamic equilibrium

Answer 4

1) Reaction takes place in a closed system
2) A constant concentration of reactants and products (they do not have to be the same concentrations)
3) Reaction proceeds on a microscopic scale
4) No change of macroscopic properties (e.g colour)
5) Reaction does not go to completion

Question 5

Provide two examples of dynamic equilibrium

Answer 5

1) Changes of state in closed systems: e.g In a closed system, the rate of evaporation and condensation of water eventually become equal
2) Saturated solutions: The rate of ions in a lattice crystallising and dissolving is the same, as the max amount of solute has been dissolved and no further solute can be dissolved.

Question 6

Provide 3 examples of irreversible reactions:

Answer 6

1) Combustion reactions (spontaneous & exothermic)
2) Photosynthesis reactions (non-spontaneous & endothermic)
3) Burning of steel wool

Question 7

Name the 2 characteristics present in the reaction rate of an irreversible reaction

Answer 7

• Reactant is consumed quickly but as it approaches zero, it plateaus
• Amount of product formed depends on amount of initial reactant present

Question 8

Name the 3 characteristics present in the reaction rate of an reversible reaction

Answer 8

• Initially only A is present & it reacts to form B
• As soon as B is formed, it reacts in the reverse direction to form A
• At equilibrium (when both concen. plateau), they continue to react in both forward and reverse dir, just at a microscopic level.

Question 9

A reaction is favoured and spontaneous if…

Answer 9

1) Entropy is increases (ΔS>0)
2) It is exothermic (ΔH<0)

Question 10

A reaction is NOT favoured & NON-spontaneous if…

Answer 10

1) Entropy decreases (ΔS<0)
2) It is endothermic (ΔH>0)

Question 11

When G=0 (Gibbs free energy):

Answer 11

2 reactions are occurring at the same time (reactants can form products, products can form reactants), i.e dynamic equilibrium

Question 12

Spontaneity of a reaction is determined by…

Answer 12

If ΔG<0, reaction occurs spontaneously
If ΔG>0, will NOT occur spontaneously