Energy changes

Entropy

The freedom of movement possessed by the molecules or atoms within a system.

Equation for ∆S

∆sTotal = ∆Sproducts - ∆Sreactants

Units: JK^-1 mol^-1

Order of entropy

Solid<Liquid<Gas

Increase in S

More freedom of movement

Decrease in S

Less freedom of movement

More entropy

More moles of gas

Is entropy more likely to increase or decrease in an isolated system.

Increase - more freedom of movement, bonds break, releasing energy, endothermic.

Gibbs Free Energy

∆G = ∆H - T∆S

Units = KJ mol^-1

Spontaneous Reaction

A reaction that once started, will go off on its own accord, without the need to continuously input energy.

For a spontaneous reaction to occur ∆G must be negative.

What does Gibbs Free Energy allow us to do?

Will allow us to determine whether or not a reaction will proceed spontaneously.

How to determine is salt is dissolvable?

For salt to dissolve in water, ∆G must be negative, this is because salt dissolving is a spontaneous reaction.

Reactions with a large Kc

Position of equilibrium lies to the right, so ∆G is likely to be negative. (Forwards reaction is occurring)

Reactions with small Kc

Position of equilibrium lies to the left, So ∆G is likely to be positive. (Backwards reaction is occurring)