Spontainety, Entropy and Free Energy

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Spontainety, Entropy and Free Energy by Mind Map: Spontainety, Entropy and Free Energy

1. Thermodynamics

1.1. Tells us whether a reaction is spontaneous based only on the properties of reactants and products.

1.2. Lets us predict the direction in which a process will occur but gives no information about the speed of the process.

1.3. Function that describes the number of arrangements that are available to a system existing in a given state.

1.4. Second Law of Thermodynamics

1.4.1. The entropy of the universe increases in a spontaneous process and remains unchanged in an equilibrium process.

1.4.2. Spontaneous process: DSuniv = DSsys + DSsurr > 0

1.4.3. Equilibrium process: DSuniv = DSsys + DSsurr = 0

1.5. Third Law of Thermodynamics

1.5.1. The entropy of a perfect crystal at 0 K is zero

1.5.2. The entropy of a substance increases with temperature.

2. Spontaneous Processes

2.1. A spontaneous process is one that occurs without outside intervention.

2.2. Spontaneous Physical and Chemical Processes in living sistem

2.2.1. A waterfall runs downhill

2.2.2. A lump of sugar dissolves in a cup of coffee

2.2.3. At 1 atm, water freezes below 0 0C and ice melts above 0 0C

2.2.4. Heat flows from a hotter object to a colder object

2.3. Nature spontaneously proceeds toward the states that have the highest probabilities of existing.

3. Entropy

3.1. The driving force for a spontaneous process is an increase in the entropy of the universe.

3.2. A measure of molecular randomness or disorder.

3.3. Standard Entropy Values (S°)

3.3.1. Represent the increase in entropy that occurs when a substance is heated from 0 K to 298 K at 1 atm pressure. ΔS°reaction = ΣnpS°products – ΣnrS°reactants

4. Free Energy

4.1. Delta Suniv= - Delta G/T (at constant T and P)

4.2. A process (at constant T and P) is spontaneous in the direction in which the free energy decreases. – Negative ΔG means positive ΔSuniv

4.3. Standard Free Energy Change (ΔG°)

4.3.1. The change in free energy that will occur if the reactants in their standard states are converted to the products in their standard states.

4.4. Free Energy and Pressure

4.4.1. G = G° + RT ln(P) or ΔG = ΔG° + RT ln(Q)

4.5. The Meaning of ΔG for a Chemical Reaction

4.5.1. A system can achieve the lowest possible free energy by going to equilibrium, not by going to completion.

4.5.2. The equilibrium point occurs at the lowest value of free energy available to the reaction system.

4.5.3. ΔG = 0 = ΔG° + RT ln(K) ΔG° = –RT ln(K)

4.6. Change in Free Energy to Reach Equilibrium

4.6.1. DG = DG0 + RT lnQ R is the gas constant (8.314 J/K•mol);T is the absolute temperature (K); Q is the reaction quotient

4.6.2. At Equilibrium Delta G = 0 Q = K 0 = DG0 + RT lnK DG0 = - RT lnK