Enthalpy, Entropy and Gibbs Free Energy

Will the entropy of this process be positive or negative? [sugar dissolving in tea]

positive entropy - dissolved sugar is more disordered

Will the entropy of this process be positive or negative? [frost forms on a window pane]

negative entropy - water going from gas to solid

Will the entropy of this process be positive or negative? [air pumped into a tire]

negative entropy - gas entering a smaller space and under more pressure

Will the entropy of this process be positive or negative? [acetone evaporates from nail polish remover]

positive entropy - acetone going from liqiod to a gas

Will the entropy of this process be positive or negative? [N2 (g) + 3H2 (g) --> 2NH3 (g)]

negative entropy - going from 4 moles of gas to 2 moles of gas

Entropy is ______.

a measure of disorder or randomness.

Enthalpy is ______.

energy released or absorbed during a chemical reaction (ΔH)

A negative ΔH means

the reaction is exothermic

A positive ΔH means

the reaction is endothermic

Exothermic reactions _______ energy.

release

Endothermic reactions ______ energy.

absorb

Enthalpy change equation

ΔH = Σ H(products) - H(reactants)

A negative ∆S

decrease in randomness or decrease in entropy

A positive ∆S

increased randomness or increase in entropy

Entropy change equation

∆S = S(products) - S(reactants)

Gibbs Free Energy is how we can calculate the ________ of a reaction.

spontineity

Gibbs Free Energy equation

ΔG = ΔH - TΔS

In spontaneous reactions, energy is _____ in the products than the reactants.

lower

In nonspontaneous reactions, energy is _____ in the products than the reactants.

higher

Exergonic reaction

A spontaneous chemical reaction in which there is a net release of free energy.

Endergonic reaction

A non-spontaneous chemical reaction in which free energy is absorbed from the surroundings.

∆G < 0

spontaneous, exergonic

∆G > 0

non-spontaneous, endergonic

Reactions are favored (spontaneous) when

∆H < 0 and ∆S > 0

Spontaneity is determined by three factors:

1. Enthalpy (∆H)

2. Temperature (T)

3. Entropy (∆S)