17.5 Gibbs Free Energy

which of the following conditions are specified by standard state conditions?

-solutions are at a concentration of 1 M -gases are at a pressure of 1 atm -the standard state of an element is its most stable allotropic form at standard state temperature and pressure

gas standard state

1 atm pressure

solution standard state

1 molar concentration

the standard free-energy change for a reaction is the free-energy change for the reaction under standard-state conditions, which assumes that all gases are at --- atm of pressure and all solutions have a concentration of --- M

1; 1

in this context, free energy is the energy

available to do work

the sign of which quantity indicates whether or not a particular reaction or process will occur spontaneously?

change in G

the change in free energy (change in G) of a system for a constant-temperature process is

change in G= change in H - T(change in S)

elements standard state

change in Gf (standard free-energy formation)=0

in order to predict the sign of change in G, we need to know both --- and ---

change in H; change in S

a negative value of change of G (with open circle) tells us whether the products or the reactants are favored when the reacting system reaches ---

equilibrium

if a given reversible reaction has positive values for both change in H and change in S, the value of change in G will become --- negative as temperature increases, and the formation of the --- will be increasingly favored

more; products

if both change in H and change in S are positive, then change in G will be --- only when the --- term is --- in magnitude than ---. This condition is met when T is ---.

negative; T(change in S); greater; change in H; large

if change in H is negative and change in S is negative, then change in G will be --- only when --- is --- in magnitude than ---. This condition is met when T is ---.

negative; T(change in S); smaller; change in H; small

if change in H is negative and change in S is positive, then change in G will always be --- regardless of ---

negative; temperature

under --- conditions, we must use the sign change in G rather than change of G (with open circle) to predict the direction of the reaction

nonstandard-state

if change in H is positive and change in S is negative, change in G will always be ---, regardless of ---

positive; temperature

liquid standard state

pure liquid

solid standard state

pure solid

a reaction with a positive vale of delta G circle will favor --- at equilibrium, while a reaction with a negative value of delta G circle will favor --- at equilibrium

reactants; products

Like H and S, G is a

state function

the Gibbs free energy change of G allows us to determine the spontaneity of a process based on thermodynamic changes to the ---

system only

in the Gibbs free energy equation ( change in G = change in H - T(change in S), the terms change in H and change in S refer to the enthalpy change and entropy change of the --- and ---, respectively

system; system

standard free-energy of reaction

the free energy change for a reaction when it occurs under standard-state conditions, when reactants in their standard states are converted to products in their standard states

standard free-energy of formation

the free energy change that occurs when 1 mole of the compound is synthesized from its elements in their standard states

correctly define the standard free-energy of formation for a substance

the free-energy change that occurs when 1 mole of the compound is formed from its elements in their standard states

meaning of the change in G (with an open circle) when it is positive

the reaction favors reactants at equilibrium

change in G>0

the reaction is nonspontaneous; the reaction is spontaneous in the opposite direction

change in G<0

the reaction is spontaneous in the forward direction

meaning of change in G when it is negative

the reaction will occur spontaneously

change in G=0

the system is at equilibrium; there is no net change

Gibbs free energy (G) or free energy equation

G=H-TS

in order to express the spontaneity of a reaction more directly, we introduce another thermodynamic function called

Gibbs free energy (G) or simply free energy