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]
organic spectroscopy tutorial all along with the key concepts of interaction of light and matter, properties of light, infrared absorption spectroscopy, infrared light absorption and molecular structure, determination of molecular structure, nuclear magnetic resonance spectroscopy
tutorsglobe.com cell structure and pigmentation assignment help-homework help by online algae tutors
tutorsglobe.com modulation natures assignment help-homework help by online modulation tutors
tutorsglobe.com function of finance department assignment help-homework help by online financial management tutors
Theory and lecture notes of Long-Run Effects of Deficits all along with the key concepts of Policy Mix-Deficits, Economic Growth, Full-Employment Deficits Reduce Investment, Persistent Deficits on Economic Growth. Tutorsglobe offers homework help, assignment help and tutor’s assistance on Long-Run Effects of Deficits.
avail affordable managerial economics assignment help service with 24x7 support of phd experts to score notable grades!
Wondering where to get the top-notch Employment Law Assignment Help at viable rates? Approach TutorsGlobe right away!
elements of group 17 tutorial all along with the key concepts of occurrence, extraction and uses of group 17, preparation of fluorine, physical properties of group 17, oxidation states and oxidation power
Biology tutorial tutorial all along with the key concepts of Development of Sperm, Development of the egg, Gamete Interaction, Sperm-egg fusion, Egg activation and pronuclei formation, formation of gametes, zona pellucida and spermiogenesis
Op-Amp Applications tutorial all along with the key concepts of Constant-Gain Multiplier, Multiple-stage Gains, Voltage Summing, Voltage Buffer, Voltage-Controlled Current Source, Current-Controlled Voltage Source, DC and AC Millivoltmeter, Low-Pass Filter, Notch Filter
www.tutorsglobe.com offers software requirements specification homework help, assignment help, case study, writing homework help, online tutoring assistance by computer science tutors.
www.tutorsglobe.com offers types of coupling homework help, assignment help, case study, writing homework help, online tutoring assistance by computer science tutors.
Recording Seismic Signals tutorial all along with the key concepts of Single-Channel Seismographs, Multi-Channel Seismographs
tutorsglobe.com utility and utility functions assignment help-homework help by online choices and preferences of consumer tutors
It is apparent that chromosomes are the movers of genetic material. Chromosomes consists proteins, DNA and RNA.
1939373
Questions Asked
3689
Tutors
1483734
Questions Answered
Start Excelling in your courses, Ask an Expert and get answers for your homework and assignments!!