Gibbs free energy (
G ) is a state function defined with regard to system quantities only and may be used to predict the spontaneity of a process. A negative value for Δ
G indicates a spontaneous process; a positive Δ
G indicates a nonspontaneous process; and a Δ
G of zero indicates that the system is at equilibrium. A number of approaches to the computation of free energy changes are possible.
Key equations
Δ
G = Δ
H −
T Δ
S
Δ
G = Δ
G ° +
RT ln
Q
Δ
G ° = −
RT ln
K
Chemistry end of chapter exercises
What is the difference between Δ
G , Δ
G °, and
for a chemical change?
A reactions has
= 100 kJ/mol and
Is the reaction spontaneous at room temperature? If not, under what temperature conditions will it become spontaneous?
The reaction is nonspontaneous at room temperature.
Above 400 K, Δ
G will become negative, and the reaction will become spontaneous.
Use the standard free energy of formation data in
Appendix G to determine the free energy change for each of the following reactions, which are run under standard state conditions and 25 °C. Identify each as either spontaneous or nonspontaneous at these conditions.
Use the standard free energy data in
Appendix G to determine the free energy change for each of the following reactions, which are run under standard state conditions and 25 °C. Identify each as either spontaneous or nonspontaneous at these conditions.
(a) Determine the standard free energy of formation,
for phosphoric acid.
(b) How does your calculated result compare to the value in
Appendix G ? Explain.
(a) −1124.3 kJ/mol for the standard free energy change. (b) The calculation agrees with the value in
Appendix G because free energy is a state function (just like the enthalpy and entropy), so its change depends only on the initial and final states, not the path between them.
if three forces F1.f2 .f3 act at a point on a Cartesian plane in the daigram .....so if the question says write down the x and y components ..... I really don't understand
a fixed gas of a mass is held at standard pressure temperature of 15 degrees Celsius .Calculate the temperature of the gas in Celsius if the pressure is changed to 2×10 to the power 4