What is Helmholtz energy: Definition and 12 Discussions
In thermodynamics, the Helmholtz free energy (or Helmholtz energy) is a thermodynamic potential that measures the useful work obtainable from a closed thermodynamic system at a constant temperature (isothermal). The change in the Helmholtz energy during a process is equal to the maximum amount of work that the system can perform in a thermodynamic process in which temperature is held constant. At constant temperature, the Helmholtz free energy is minimized at equilibrium.
In contrast, the Gibbs free energy or free enthalpy is most commonly used as a measure of thermodynamic potential (especially in chemistry) when it is convenient for applications that occur at constant pressure. For example, in explosives research Helmholtz free energy is often used, since explosive reactions by their nature induce pressure changes. It is also frequently used to define fundamental equations of state of pure substances.
The concept of free energy was developed by Hermann von Helmholtz, a German physicist, and first presented in 1882 in a lecture called "On the thermodynamics of chemical processes". From the German word Arbeit (work), the International Union of Pure and Applied Chemistry (IUPAC) recommends the symbol A and the name Helmholtz energy. In physics, the symbol F is also used in reference to free energy or Helmholtz function.
Summary:: Gibbs and Helmholtz energies calculations for heating an ideal gas at constant volume
I am solving a problem involving an ideal gas that undergoes several chained changes of state. One of the steps asks to calculate the change in Gibbs Energy (DeltaG) and Helmholtz energy (Delta A)...
Hello, so first of all I want to clarify that english is not my first lenguage, so I'm really sorry for possible future errors. Second, this is a problem from my physical chemistry class, and I'm not sure where it fits better, if here or in the physics homework help, I'm sorry :(
So, I don't...
Homework Statement
This is a state ecuation of a gas:
PV=AT+B/V, where A and B there are constants.
First: Demonstrate that ##c_V## depends only of T
Second: Find U(T,V) and S(T,V)
Homework Equations
##\left(\frac{\partial U}{\partial S}\right)_V=T\text{ (1)}##
##\left(\frac{\partial...
Homework Statement
Show that for a reaction occurring at constant T and V, F is minimized at equilibrium.
Homework Equations
##F=U-TS##
##TdS=dU+pdV-\mu dN##
The Attempt at a Solution
##dF=dU-d(TS)=dU-TdS-SdT=dU-dU -pdV+ \mu dN -S dT=-pdV - SdT + \mu dN##. At constant T and V this reduces to...
The problem is :
a) Find Helmholtz free energy F(V, T) of a simple solid.
b) Use the result of part a) to verify that (∂F/∂T)v and (∂F/∂V)T are consistent with S(T, V) and P(V, T) in equation P=a0T-b0ln(V/V0)
I know:
Helmholtz free energy is F=U-TS
and dF=-SdT-PdV
S=-((∂F/∂T)v)...
Homework Statement
The 4 fundamental equations of thermodynamics are:
dE = TdS - PdV
dH = TdS + VdP
dG = VdP - SdT
dA = - PdV - SdT
Supose a gas obeys the equation of state
P = \frac{nRT}{V} - \frac{an^{2}}{V^{2}}
Use one of the fundamental equations to find the change in Helmholtz energy...
Homework Statement
Define the Helmholtz free energy as F=E-TS.
Show that the internal energy E=-T2\frac{∂}{∂T}(\frac{F}{T})V
Homework Equations
S=(\frac{∂F}{∂T})V
Perhaps \beta=\frac{1}{\tau}
and \tau=kBT
The Attempt at a Solution
E = F+TS
E = F+T(\frac{∂F}{∂T})V
.
.
. (some...
I'm confused about the condition for spontaneity for the Helmholtz energy. My textbook (McQuarrie, "Physical Chemistry") derives the conditions as follows. We start with the combined law of thermodynamics:
dU = δq + δw ≤ TdS – PdV since δq/T ≤ dS
dU – TdS + PdV ≤ 0
For a process at...
I'm having some trouble understanding this concept. Why is it that you sometimes can get heat for free from the environment? Like suppose you have a system, on which you make an energyconsuming proces which creates entropy. Then you subtract TΔS because apparently heat can enter when the entropy...
Homework Statement
Explain why the formula (dF/dV)=-P , where T and N are constant variables , makes intuitive sense, by discussing graphs of F vs. V with different slopes.
Homework Equations
The Attempt at a Solution
dF=SdT-PdV+mu*dN
dT and DN are zero since T and N are...