Equilibrium Definition and 1000 Threads

Thermodynamic equilibrium is an axiomatic concept of thermodynamics. It is an internal state of a single thermodynamic system, or a relation between several thermodynamic systems connected by more or less permeable or impermeable walls. In thermodynamic equilibrium there are no net macroscopic flows of matter or of energy, either within a system or between systems.
In a system that is in its own state of internal thermodynamic equilibrium, no macroscopic change occurs.
Systems in mutual thermodynamic equilibrium are simultaneously in mutual thermal, mechanical, chemical, and radiative equilibria. Systems can be in one kind of mutual equilibrium, though not in others. In thermodynamic equilibrium, all kinds of equilibrium hold at once and indefinitely, until disturbed by a thermodynamic operation. In a macroscopic equilibrium, perfectly or almost perfectly balanced microscopic exchanges occur; this is the physical explanation of the notion of macroscopic equilibrium.
A thermodynamic system in a state of internal thermodynamic equilibrium has a spatially uniform temperature. Its intensive properties, other than temperature, may be driven to spatial inhomogeneity by an unchanging long-range force field imposed on it by its surroundings.
In systems that are at a state of non-equilibrium there are, by contrast, net flows of matter or energy. If such changes can be triggered to occur in a system in which they are not already occurring, the system is said to be in a meta-stable equilibrium.
Though not a widely named "law," it is an axiom of thermodynamics that there exist states of thermodynamic equilibrium. The second law of thermodynamics states that when a body of material starts from an equilibrium state, in which, portions of it are held at different states by more or less permeable or impermeable partitions, and a thermodynamic operation removes or makes the partitions more permeable and it is isolated, then it spontaneously reaches its own, new state of internal thermodynamic equilibrium, and this is accompanied by an increase in the sum of the entropies of the portions.

View More On Wikipedia.org
Recent contents Top users
  1. M

    Phenol Removal with an equilibrium stage

    Homework Statement Homework Equations The Attempt at a Solution The problem here is that it looks like having 2 equilibrium stages requires the same flow ratio as one equilibrium stage, according to my calculations. This seems strange to me, so I am wondering if I am wrong. I also am not sure...
  2. Q

    How Much CCl4 Remains Liquid at Equilibrium in a Sealed Flask?

    Homework Statement If 5.00 mL of liquid carbon tetrachloride (CCl4, density = 1.587 g/mL) was injected into a sealed 5.00 L flask at 30.0°C, what volume (if any) of the CCl4 would remain as liquid after equilibrium is reached? (the vapor pressure of CCl4 at 30.0°C is 143.0 mmHg) Homework...
  3. I

    What Causes Incorrect Section Placement in Static Equilibrium and Torque?

    wrong section
  4. L

    Statics- equilibrium of rigid bodies

    Homework Statement An opening in a floor is covered by a 1×1.2-m sheet of plywood of mass 18 kg. The sheet is hinged at A and B and is maintained in a position slightly above the floor by a small block C. Determine the vertical component of the reaction (a) at A, (b) at B, (c) at C.Homework...
  5. C

    Difference between electrochemical equilibrium and chemical equilibriu

    1. What is electrochemical equilibrium and what is chemical equilibrium? 2.What are the differences between the two above? 3. The difference between the two i think is electrochemical equilibrium is a state whereby the electrical charge in both compartments are equals. Wherease...
  6. T

    How Do You Calculate the Mass of a Beam in Static Equilibrium?

    Homework Statement Suppose we take a 1 m long uniform bar and support it at the 22 cm mark. Hanging a 0.29 kg mass on the short end of the beam results in the system being in balance. Find the mass of the beam. Homework Equations \tau=F*r The Attempt at a Solution I set it up so that...
  7. M

    How Does Pressure Remain Constant During a Phase Transition?

    In reference to the graph at the bottom, my textbook has a statement '''..A process of vaporization or condensation at a constant temperature is illustrated by the lines G-H-I or I-H-G, respectively, in figure 16.3. Water would vaporize or condense at a constant temperature as the...
  8. M

    Can a Solid Reach Equilibrium Below the Triple Point?

    How is it that a solid can be in equilibrium below the triple point? Why can't liquid form? It seems odd to me that the molecules can go to a vapor, but not a liquid. It seems like the molecules can sublime more freely than they can melt. Can someone explain this from a molecular view point?
  9. C

    What Is the Equilibrium Concentration of H2(g) at 1000°C?

    Homework Statement consider the following reaction: 2H2O(i) <-> 2H2(g) + O2(g) kc=7.3*10^-18 at 1000oC The initial concentration of water in a reaction vessel is 0.055 mol/L. What is the equilibrium concentration of H2(g) at 1000oC? Homework Equations h20 h2...
  10. W

    Why is the Fermi level a constant in thermal equilibrium?

    Why is the Fermi level a constant in thermal equilibrium? just like PN diode (P=material 1 ; N=material 2) the fermi levels are the same (Ef1=Ef2) in thermal equilibrium i confused that why there is no energy transfer so that can judge each energy E will obey rate from 1 to 2 ~...
  11. L

    Statics Problem, two disks in equilibrium

    Homework Statement http://imgur.com/yVOXkAT The two disks each have a mass of 18kg and are attached at their centers by an elastic cord that has a stiffness of k = 1.6kN/m . Determine the stretch of the cord when the system is in equilibrium and the angle θ of the cord. (Figure 1)...
  12. W

    Osmotic Pressure and Equilibrium constant

    Homework Statement An aqueous solution contains 0.84 g/L of an organic detergent. The osmotic pressure of this solution is 54.4 torr, at 25°C. What is the molar mass (in g/mol) of this detergent? Homework Equations ##pi=MRT## ##R=0.08206L*atm/(mol*K)## The Attempt at a Solution...
  13. V

    MHB Equilibrium solution limit to differential equation

    Can someone please help me with this one? I have found the equilibrium solutions,but I'm not sure what to do next. Consider dx/dt = x^3 - 4x Given a solution x(t) which satisfies the condition x(0) = 1, determine the limit(t -> infinity) of x(t). Thanks!
  14. FeDeX_LaTeX

    Finding Equilibrium Points and Sketching Phase Portrait for a System of DEs

    Homework Statement Find the equilibrium points of the system, determine their type and sketch the phase portrait. ##\frac{dx}{dt} = -3y + xy - 10, \frac{dy}{dt} = y^2 - x^2## The attempt at a solution Putting it together: ##\frac{dy}{dx} = \frac{y^2 - x^2}{-3y + xy - 10} \equiv...
  15. C

    How Much CO Remains at Equilibrium in a 3L Flask?

    Homework Statement H2+CO2=CO+H2O if 1.50 mol of each chemical species are placed in a 3.00l flask and allowed to achieve the equilibrium above, what mass of Co will be present at equilibrium? Homework Equations Keq= concentration of products each raised to the number of moles in...
  16. C

    Determining stable and unstable equilibrium points

    Background: I've derived the equation of motion of the bead shown in the picture below using the Lagrangian \omega^2Rsin(\theta)+r\ddot{\theta}=0 The equilibrium points are at θ=0 and π. I'm now to show that only one of these points is stable. Homework Statement Show that only one of the...
  17. R

    Equilibrium equation for forces in tangential direction

    Homework Statement Derive the differential equilibrium equation in the tangential direction \theta Homework Equations \sum F_\theta = 0 V = 1/2(2r + \Delta r)\Delta r \Delta \theta Small angle approximation: \cos(\frac{\Delta \theta}{2}) = 1 \sin(\frac{\Delta \theta}{2})...
  18. J

    Stable Equilibrium: Definition & Physical Meaning

    What is the physical meaning of an object to be in stable equilibrium? Would it make sense to say that the object wants to stay at that position and any movement will cause the restoring force to move the object back to equilibrium?
  19. U

    Finding Reaction Forces in 3D Equilibrium: Solving a Tricky Bent Rod Problem

    Homework Statement in the attached picture are all the information needed to solve the problem. The bent rod of a negligible weight is supported by a ball and a socket joint at A and a single journal bearing at B. End of D of the rod rests against a friction-less vertical surface. find...
  20. K

    Finding the Unknown Angle in Equilibrium for Symmetrical Bars Under Load

    Homework Statement Trying to find angle u of bars (symmetrical) with ground at equilibrium under load. Two bars, negligible weight of length .4m Spring at midpoint k = 3kN/m, unstretched when bars at 45 deg F = 150N, 5 deg W of block 10kg Slope of ground under block 5 deg coef friction...
  21. M

    Equilibrium the ultimate conversion

    Hello, I am wondering conceptually why the maximum conversion of products is made at chemical equilibrium? I was thinking if you use le chatelier to push towards products, the conversion will be higher. Sorry if this sounds too vague, my prof's lecture was called "Equilibrium: The ultimate...
  22. M

    Equilibrium conversion in reactor

    Homework Statement The gas stream from a sulfur burner is composed of 15-mol% SO2, 20-mol% O2, and 65-mol% N2. This gas stream at 1 bar and 480 C enters a catalytic converter, where the SO2 is further oxidized to SO3. Find the equilibrium conversion of SO2. The equilibrium constant for...
  23. L

    Solve Equilibrium Problem: Find Alpha Range (27.4-222.6)

    Homework Statement http://puu.sh/4NWw9.PNG question 2.65** Homework Equations I've tried using the law of sine and law of cosine method with the triangle for equilibrium and I've tried the 600^2 = Fx^2 + Fy^2 The Attempt at a Solution Here is what I did using the F^2 = Fx^2 + Fy^2...
  24. V

    Equilibrium of frame with two masses

    Homework Statement I need to find the tension T, γ and β in part 2 of this question. The question is attached. Homework Equations First of all, the frame is a right angle triangle because (3L)^2 + (4L)^2 = (5L)^2 take torque about the point O we got 2LF + mg(4Lcosγ) = Mg(3Lsinγ) from...
  25. G

    Thermodynamical Equilibrium

    A cylinder has rigid, adiabatic and impermeable external walls. It is provided with a mobile internal ideal partition wall, dividing it in two volumes (A and B). Each volume is filled with an ideal monoatomic gas. Initially, the volume, pressure and temperature of A and B are identical...
  26. L

    Liouville equation - equilibrium

    Hi! I have problem with uderstanding of Liouville equation. Which sais that if we have a Hamiltonian system (energy is conserved), then the the volume of phase space is conserved, or equivalently the probability density is conserved (the total derivative of probability density per time is...
  27. E

    Archived How Much Weight Can a Walkway Hold Before Balance Is Lost?

    This problem is trying to find out how much weight can be placed in the middle of a system before the weights on the outside go over the pulleys. A diagram of the problem can be found here...
  28. Y

    How to Find Equilibrium Pressures for NO₂ and N₂O₄ at 298 K?

    Homework Statement For the reaction 2 NO_{2}(g) \leftrightarrow N_{2}O_{4}(g) ΔH°_{rxn} = -57.2 kJ and ΔS°_{rxn} = -175.8 J/K A 1 L container is initially filled with 1 atm of NO_{2} at 298 K. Find the equilibrium pressures of NO_{2} and N_{2}O_{4} at 298 K if a. volume is held...
  29. U

    Why is equilibrium constant K a product of the concentrations?

    So in a given amount of solution, the equilibrium constant is the product of the concentrations of the ionic species present, raised to the power of the stoichiometric coefficient. Wouldn't it make more sense if it was the sum of the concentrations though,since basically the net number of ions...
  30. M

    Force required to maintain Equilibrium

    My problem here is that I keep trying to make substitutions for the normal forces and cannot come up with the number for P. I saw 4.92 and don't understand how there is a range of force for which equilibrium can be maintained. The force I came up with for P is way too big, the answer is 0.955 lb
  31. N

    Differential equation bifurcation, how to find equilibrium points?

    Homework Statement What are the bifurcation values for the equation: dy/dt = y^3 +ay^2 Homework Equations The Attempt at a Solution Equilibrium solutions: y^3 + ay^2 = 0 ==> y^2 (y + a) = 0 ==> y = 0 (double root), or y = -a. a = 0 is the sole bifurcation point, since...
  32. B

    Equilibrium Solutions - Understand & Graphically Visualize

    Hello, I want to make certain of my understanding of equilibrium solutions. Are equilibrium solutions the value(s) of y such that \frac{dy}{dt} = 0? So, suppose y = y0 is one of those solutions. Graphically, does this mean that one the horizontal line y = y0, little slope lines are too...
  33. M

    What Is the Weight Attached in a Pulley Traction System in Equilibrium?

    Homework Statement Sum of downward forces exerted at A and B is 41lbs by the leg, what is the weight attached? Homework Equations None, really... The Attempt at a Solution Tension (T) throughout the system must be constant and equal to the weight (W). I first assumed that the leg...
  34. burnst14

    Equilibrium of a Rod Problem: Find Minimum Distance x

    Problem Statement: As shown in the figure below, a uniform beam is supported by a cable at one end and the force of friction at the other end. The cable makes an angle of θ = 30°, the length of the beam is L = 1.50 m, the coefficient of static friction between the wall and the beam is μs =...
  35. C

    When can you assume dynamic equilibrium?

    SOLVED Homework Statement A 23 kg child goes down a straight slide inclined 38∘ above horizontal. The child is acted on by his weight, the normal force from the slide, and kinetic friction. Find the magnitude of the normal force. Homework Equations cos(theta)=adjacent/hypotenuse The...
  36. 0

    Static Equilibrium Two Pulleys and Weights With Ring

    I have a problem. Lets say there were two pulleys put at equal height. You have a metal ring and attach three wires to it. At the end of each wire, have three weights of mass w. One weight hangs down, one weight goes over one pulley and the other over the other pulley. The system goes to...
  37. N

    Equilibrium radioactive decay question

    Homework Statement A sample of Mo-101, initially pure at time zero, beta decays to Tc-101 which then beta decays to Ru-101 (stable). The half-lives of Mo-101 and Tc-101 are nearly the same and for this problem are assumed equal (14.4 min). After a decay period of one half-life how many atoms...
  38. S

    Why does altering permeability of an ion affect equilibrium potential

    It seems to me that change in permeability should not shift the equilibrium of entering and exiting ions, except how fast equilibrium is reached. Consider this: two compartments are separated by a membrane. 1st compartment holds 1mM Na+ and 10mM K+ and 2nd one holds 10mM Na+ and 1mM K+. Let's...
  39. M

    How Does Height Influence Torque in Static Equilibrium?

    So with this problem, I have been thinking about it. Since it is in equilibrium, I know the sum of forces and torques will be equal to zero. However, I'm not sure how the height, h, fits into this. I know the weights have a force and are a distance away from that fulcrum, d and 2d, so I could...
  40. B

    Beam equilibrium and shear force

    Homework Statement transverse loads are applied to the beam in the figure at A, C, and E, and a concentrated couple 3Pa is applied to the beam at E. Determine expressions for (a) the transverse shear force Vc and bending moment Mc at a section just to the left of the load at C, and (b) shear...
  41. D

    Calculating Reaction Force on a Stationary Wall in a Rotating System

    Hello, I am a first time poster and I need some help with a basic statics problem. I drew a free body diagram to help illustrate. An object with a mass 'M' is resting on a rotating disc that is spinning with constant velocity 'V'. The mass is continuously being pushed into a static wall due...
  42. M

    Is thermal equilibrium possible by the Law of Cooling?

    Law of cooling states that the rate of loss of heat by a body is directly proportional to the excess temperature of the body above that of its surroundings. The equation of determining temperature in time T(t)=Ta+(T0-Ta)*e^kt (Ta-ambient temperature, T0-initial temperature, k-heat transfer...
  43. G

    Electrostatics: Equilibrium distance & Acceleration

    Homework Statement As indicated in the diagram, consider a rail inclined at an angle θ relative to the horizontal axis. A sphere (A) with a charge +q is fixed at the bottom of the rail. A second sphere (B) with a charge +2q and a mass (m) is free to move along the rail. The sphere (C)...
  44. marellasunny

    Store equilibrium points of a 3D system in a (x,y,z) array

    I have a complicated 3d nonlinear differential system which I solve algebraically using maple's solve command. I aim to find the equilibrium points of the system using MAPLE and then plot these equilibrium points as a function of the 3 parameters alpha,beta,gamma(a.k.a.bifurcation diagram). The...
  45. J

    Equilibrium Problems: Get Help Solving Questions

    Hi guys wondering if anyone can help me with this question that I am stuck on just not sure were to start.
  46. W

    Equilibrium, Charge Balance, Mass Balance

    Homework Statement Write the charge balance for a solution containing H(+), OH(-), Ca^(2+). HCO3(-). CO3^(2-) , Ca(HCO3)+, Ca(OH)+, K+, and CIO4(-).Homework Equations Also, I am having a trouble understanding the concepts of mass balance and charge balance. The Attempt at a Solution The...
  47. B

    Calculating Moles Ratio of Reactants for Yield f in K Equilibrium

    If I want to calculate the number of moles ratio of reactants which, in a reversible reaction of equilibrium constant K, will give me a certain yield 'f', what is the mathematical definition of the yield in this case? For instance, in the reaction A + B ⇔ C + D, let's say we can denote extent...
  48. N

    Charge distribution along a square loop in equilibrium

    Homework Statement A conductor (wire) is folded into a square loop with each side having a length of a. Total charge of Q is transferred onto the conductor. Describe the line charge density of the square loop in equilibrium. (If I am interpreting this correctly what is required is...
  49. B

    Redox Equilibrium Homework Solutions

    Homework Statement I.) Give an estimate for the stability constant of the complex [FeCl]2+, given that the standard redox potential for the Fe3+/Fe2+ system in 1 moldm-3 HCl is 0.710 V. The "standard electrode potential of the reaction Fe3+ + e- -> Fe2+" (quote from the question) had...
  50. S

    Gibbs free energy going to zero (equilibrium)

    Hi I have a 4 part question about phase changes and I hope you guys can help me out here thanks :) The chemical equation for vaporization for water is H2O(l)-->H2O(g) 1) When ΔG is 0 during a phase change we would use the formula ΔH=TΔS and put in values to get the boiling/melting point by...
Back
Top