Thermodynamic Potentials:
The four (4) thermodynamic potentials are:
Depending on the thermodynamic constraints on the system, it is always suitable to use the particular thermodynamic potential to explain the system. For instance Helmholtz free energy A can be utilized to explain the system in which temperature and volume are held constant. Equilibrium condition for system is dA=0. Gibbs free energy G can be utilized to explain equilibrium between phases (as two phases share same pressure and temperature).
Internal Energy U:
Internal energy U of the system is the state function i.e. it depends on state of the system. First law of thermodynamics provides the insight in internal energy of the system. Change in internal energy U of system DU, according to first law of thermodynamics is
ΔU = Q - W
And the differential form is
dU = dQ - dW
Work done on a system may include the irreversible component dWI (like stirring with a paddle, or forcing the electric current through a resistor) and some reversible components dWR. Irreversible component of work is dissipated as heat and is identical to adding heat to system. So we can write dS = (dQ + dWI)/T and this provides dQ = TdS - dWI. Reversible component of work may consist of work done in compressing system (PdV), but there may also be other types of work. Generally expression for each of these forms of reversible work is of the form XdY, where X is the intensive state variable and Y is extensive state variable. All of these forms of non dissipative work can together be known as configuration work. Thus, total work done on system is of form
dW = dWI - PdV + ΣXdY
so, the first law of thermodynamics takes the form
dU = dQ + dWI - PdV + ΣXdY
This is a kind of complete form of first law taking into consideration all possible forms of work. Using equation if the particular system is held at constant volume, then no PdV work of expansion or compression is done. And if no other sort of work is done (either non- PdV reversible work or irreversible work dWI), then increase in internal energy of this system is just equal to heat added to system.
Thus, internal energy U can be utilized to describe the system in which heat is transferred (either in or out) and / or work is done on or by system.
Enthalpy H:
Enthalpy is a heat energy exchange which occurs during chemical reactions. It has symbol H and is estimated in kJ/mol, or kilojoules per mole. Energy exchanged with surrounding environment at constant pressure is known as enthalpy change of a reaction. To estimate change, standard conditions are utilized, including the pressure of 1 atmosphere and temperature of 298 Kelvin (77°F or 25°C).
When reaction is giving off heat, it is termed as exothermic. In this case, enthalpy change is negative, as reaction is going from high energy to low energy because of the loss of heat energy to its surroundings. If energy flows from surrounding environment into the system, or heat is being taken in, it is termed as endothermic. In this case, change is positive as system is gaining energy in form of heat.
Enthalpy Formula is given by
Enthalpy change = heat of the reaction
ΔH = H2 - H1
Helmholtz Free Energy A:
The Helmholtz free energy A is stated as:
A = U - TS
Its differential form is:
dA = dU - TdS - SdT
But dU = dQ + dWI - PdV + ΣXdY so equation becomes:
dA = -SdT - PdV + ΣXdY so equation becomes:
dA = -SdT - PdV + ΣXdY
This Equation defines that in the isothermal process (i.e. when dT = 0), increase in Helmholtz function of a system is equal to all reversible work (-PdV + ΣXdY) done on system. On the other hand, if the machine does any reversible work at constant temperature, Helmholtz function decreases, and decrease in Helmholtz function is equal (if temperature is constant) to reversible work (of all types) done by system.
Gibbs free energy G:
Gibbs function is express as
PG =U - TS + V
It can also be stated as
G = H - TS and as:
G = A + PV
Its differential from equation is:
dG = dH - TdS - SdT,
By solving equation we get:
dG = -SdT + VdP + ΣXdY
This equation can be utilized to explain the system which goes through constant temperature and constant pressure processes. Example of the process of this type is phase change of pure substance which generally occurs at constant temperature and pressure. Therefore, Gibbs free function is very helpful in describing the process which involves change of phase.
Tutorsglobe: A way to secure high grade in your curriculum (Online Tutoring)
Expand your confidence, grow study skills and improve your grades.
Since 2009, Tutorsglobe has proactively helped millions of students to get better grades in school, college or university and score well in competitive tests with live, one-on-one online tutoring.
Using an advanced developed tutoring system providing little or no wait time, the students are connected on-demand with a tutor at www.tutorsglobe.com. Students work one-on-one, in real-time with a tutor, communicating and studying using a virtual whiteboard technology. Scientific and mathematical notation, symbols, geometric figures, graphing and freehand drawing can be rendered quickly and easily in the advanced whiteboard.
Free to know our price and packages for online physics tutoring. Chat with us or submit request at [email protected]
tutorsglobe.com absorption and movement assignment help-homework help by online cell as a physiological unit tutors
tutorsglobe.com natural killer cells assignment help-homework help by online natural immunity tutors
Theory and lecture notes of Arithmetic Sequences all along with the key concepts of arithmetic sequences, Partial Sum of an Arithmetic Sequence, Common Difference and General Term of Arithmetic Sequences. Tutorsglobe offers homework help, assignment help and tutor’s assistance on Arithmetic Sequences.
tutorsglobe.com hypermetropia assignment help-homework help by online errors of refraction tutors
tutorsglobe.com economic importance of algae assignment help-homework help by online algae tutors
Natural gas origin tutorial all along with the key concepts of Formation of Natural Gas, Natural Gas under the Earth, Deep Natural Gas, Tight Natural Gas, Shale Gas, Coal Bed Methane, Geopressurised Zones, Methane Hydrates, Offshore Gas Fields, Stranded Gas
Terrestrial Biomes tutorial all along with the key concepts of Definition of Biomes, Classification of Biomes, Tropical Rain Forest, Tropical Seasonal Forest, Temperate Rainforest, Savannah and Desert
Carbohydrate Chemistry tutorial all along with the key concepts of Monosaccharides, Disaccharides, Oligosaccharides, Polysaccharides, Biological significance of carbohydrate, Stereoisomerism of carbohydrates and Reactions of Carbohydrates
Tropical and Temperate Flora and Fauna tutorial all along with the key concepts of Tropical and Temperate Regions, Tropical and Temperate Flora, Tropical and Temperate Fauna, Dispersal of Plants, Means of Dispersal of Animals and Principles of Animal Distribution
Theory and lecture notes of Closure Properties of Class of CFLs all along with the key concepts of closure properties of class of cfls, Context Free Grammars & Languages, Theorem on CFL closure properties. Tutorsglobe offers homework help, assignment help and tutor’s assistance on Closure Properties of Class of CFLs.
Theory and lecture notes of Write ahead Log protocol all along with the key concepts of write ahead log protocol, recovery protocols. Tutorsglobe offers homework help, assignment help and tutor’s assistance on Write ahead Log protocol.
tutorsglobe.com enhancing distribution of income assignment help-homework help by online objectives of fiscal policy tutors
Equivalent Circuits of Transistors tutorial all along with the key concepts of Bipolar Junction Transistor, Transistor Models, Common Base Configuration, Common Emitter Configuration, Common Collector Configuration, NPN Transistor, PNP Transistor, Transistor As A Switch
tutorsglobe.com messenger rna assignment help-homework help by online structure of rna tutors
tutorsglobe.com reactions of glycolytic pathway assignment help-homework help by online glycolysis tutors
1955099
Questions Asked
3689
Tutors
1483444
Questions Answered
Start Excelling in your courses, Ask an Expert and get answers for your homework and assignments!!