5. EEE-Enthalpy And Entropy

Question 1

• standard entropy change of reaction

Answer 1

The entropy change that accompanies a reaction in the molar quantities expressed in a chemical equation under standard conditions, all reactants and products being in their standard states

Question 2

Entropy

Answer 2

A (quantitative) measure of the disorder of a system

A system becomes energetically more stable when it becomes more disordered

Question 3

Entropy change, ΔS

Answer 3

ΔS= ΣS(products) - ΣS(reactants)

Question 4

Free energy change, ΔG

Answer 4

The balance between entropy and enthalpy changes

ΔG = ΔH - TΔS

This determines the feasibility of a reaction: a process can take place when ΔG

Question 5

Spec:

How are endothermic reactions able to take place spontaneously?

Answer 5

ΔS must be positive
Temperature must be high enough so that TΔS > ΔH

Example:
ice melting is an endothermic reaction with increasing disorder and takes place at (relatively) high temperatures

Question 6

• random example:

When does entropy change?

Answer 6

With:

Change in state
Dissolving
Change in number of gaseous moles (possibly liquid too- )

Question 7

• example

Why do many dissolving processes have a negative value for ΔS?

Answer 7

Entropy increases whenever particles become more disordered

There are more ways of arranging the particles in a solution than in a solid