# What is Equilibria: Definition and 55 Discussions

Fluid Phase Equilibria is a peer-reviewed scientific journal on physical chemistry and thermodynamics that is published by Elsevier. The articles deal with experimental, theoretical and applied research related to properties of pure components and mixtures, especially phase equilibria, caloric and transport properties of fluid and solid phases. It has an impact factor of 2.838 (2019).

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1. ### Medical Question about reactions in biochemistry

we assume that we have an exergonic reaction , a substrate going to a product , is the negative ΔG′° the principal reason that the equilibrium favors the product (there is more product than substrate at equilibrium )?, or it is not and that depends on other factors? , thanks .
2. ### Dynamic Systems: Poincaré-Bendixson Theorem finite # of equilibria

Homework Statement:: Can someone explain the finite number of equilibria outcome of the Poincaré-Bendixson Theorem? Relevant Equations:: Poincaré-Bendixson Theorem [Mentor Note -- General question moved from the schoolwork forums to the technical math forums] Hi, I was reading notes in...
3. ### Chemistry Citric acid polyprotic acid equilibria

Using the first equilibrium, H3A <-> H2A- + H+, the [H+] is solved to be 0.01165 M ~ 1.1 * 10^-2 M. Using the second equilibrium, H2A- <-> HA2- + H+, the additional change in H+ is found to be 1.8 * 10^-5 M. The solution says that this second equilibrium is negligible, because 1.1 * 10^-2 M +...
4. ### Chemistry Solving pH Changes: Adding Acid to a Buffer or Water

This is for a high school chemistry class. In part a of the question, I calculated the pH of the solution to be 3.38. Part a was the question: Calculate the pH of a solution containing 0.75 M lactic acid (Ka= 1.4 *10^-4) and 0.25 M sodium lactate. For part b I am having trouble determining how...
5. ### Chemistry Comparing Physical Chemistry Textbooks: Atkins vs. Levine

I want some undergraduate level (or postgraduate level will also do) books on physical chemistry. I've got two books: one by Ira Levine and the other by Peter Atkins. But both these books contain only huge amounts of thermodynamics. Other topics are almost not touched upon. I want a book that...
6. ### Heterogeneous equilibria: concentration of solids issue

Homework Statement Hello! Here is the quote from the chemistry textbook by Tro: However, since carbon is a solid, its concentration is constant—it does not change. Adding more or less carbon to the reaction mixture does not change the concentration of carbon. The concentration of a solid...
7. ### Is this the correct explanation? (phase equilibria)

Homework Statement Given the following reaction that has reached equilibrium: NaCl(s)←→NaCl(aq). For the phase equilibrium to exist, the NaCl(aq) must be a solution that is A. concentrated B. saturated C. dilute D. heated E. unsaturated Homework Equations - The Attempt at a Solution I chose...
8. ### Kp for heterogeneous Equilibria (with (l))

Homework Statement 3Cu(s) + 2NO3-(aq) + 8H+(aq) ⇔3Cu2+(aq) + 2NO(g) + 4H2O(l) Kp and Kc relationship? does Kp exist? or HCl(g)⇔H+(aq)+Cl-(aq) Homework Equations Law of mass action, Kp=Kc(RT)Δng The Attempt at a Solution In lots of places contradictory results are there, some say that in Kp ...
9. ### Effect on equilibrium, addition of inert gas

If inert gases are added at constant volume to an equilibrium mixture, the total pressure increases. But the mole fraction of the gaseous reactants or products decrease. Partial pressure ##p=x\cdot P## where P is total pressure and ##x## is mole fraction. How can you say that ##p## remains...
10. ### Exploring the Range of Equilibrium States in Tank Systems: A Ratio Approach

Given two equilibrium equations for a tank 1 and tank 2 with ## Q^E_1 =6(9q_1 +q_2) ## and ## Q^E_2 =20(3q_1 +2q_2) ##, respectively, where ## q_1, q_2 ≧ 0 ##, describe which possible equilibrium states for various values of ## q_1 ## and ## q_2 ## are possible. I believe I know how the answer...
11. ### Why is the Particular Solution Different in Nonlinear System Equilibria?

So I'm reading the Example on page 161 of Differential Equations, Dynamical Systems and an Introduction to Chaos by Hirsh, Smale, and Devaney. I'm not understanding everything. So given the system x' = x + y^2 y' = -y we see this is non-linear. I get it that near the origin, y^2 tends to...
12. ### Exploring Equilibrium Constants & Kinetics: A Closer Look

Consider the following generic equilibrium: aM + bN ⇌ cO + dP An equilibrium constant, K, can be defined as: $$K = \frac{[O]^c [P]^d}{[M]^a [N]^b}$$ But couldn't we also define another equilibrium constant similarly with coefficients that are in the same ratio as our original equation? For...
13. ### Assumptions Built in to Solving Titration Equilibria?

I'm trying to reach a more thorough understanding of what's going on when we calculate equilibrium concentrations and was wanting to understand more what assumptions we make in order to follow through with the calculations. Let me ask off of an example: Consider mixing equal amounts of NH3...
14. ### PH of a polyprotic acid using multiple equilibria - is this correct?

Homework Statement Find the pH of 0.02025 M tartaric acid using the method of multiple equilibria given that its Ka1 value is 9.2*10-4 and its Ka2 value is 4.31*10-5. Homework Equations Kaoverall = Ka1 * Ka2 The Attempt at a Solution Please check the Word document. Is my method...
15. ### Is There Missing Information in the Ksp Equilibria AgCl Data?

Please look at attached picture. So, I tried solving it. Apparently, the answer is C. But, I think there is missing information (ie the volume of the initial solution). Care to back me up on this?
16. ### Is My Acid Equilibrium Final Review Correct?

Hello Forum! I have this review package for my final full of weird mistakes. Problem is that it is hard for me to know if the solutions are right or not: Could you please look at this problem I attached? They bizarrely switch from HA to HB. Is that just a typo? Then, the sign of DG°...
17. ### Kb: NH3+H2O<=>NH4++OH-: Why Omit H2O?

Why is it that for the constant Kb, we always have to write H2O in the equation and we can omit H2O in acid reactions: My textbook always writes: NH3+H2O<=>NH4++OH- NH4+<=>NH3+H+ Why can we not write NH3+H+<=>NH4+?
18. ### How Much AgBr Can Dissolve in 1.0 L of 0.40 M NH3?

Homework Statement How much AgBr could dissolve in 1.0 L of 0.40 M NH3? Assume that Ag(NH3)2+ is the only complex formed. [Kf=1*108 ; Ksp=5*10-13] Homework Equations The Attempt at a Solution Let Ag+ and Br- formed from AgBr be x. Since Ag+ form a complex with NH3, let the amount of Ag+...
19. ### What is the relationship between equilibrium constant and phase diagrams?

On a phase diagram, the lines are "lines of equilibrium", i.e. at any point on these lines of equilibrium there is an established equilibrium between the two phases on either side of the line. The equilibrium constant is a function of temperature and pressure, and the various other thermodynamic...
20. ### Aqueous equilibria, buffered solutions

I have two problems. Homework Statement How many moles of Na2CO3 must be dissolved in 250 mL of 0,125 M NaHCO3 so that the solution has a pH of 10,00? Homework Equations The powers of the concentrations are the coefficients in the chemical equation. The products of the...
21. ### Solving H2O Equilibria: Can 5 Variables be Balanced?

If we have an acid-base aqueous equilibrium system and decide to treat the concentration of H2O as a variable, does it then become impossible to solve for all the concentrations? Or can we write an equation to help us? e.g. HA is added to water. Mass Balance: CHA=[HA]+[A-] Charge Balance...
22. ### Chemical and phase equilibria, A12 and A21 for Infinitely dilute.

Homework Statement (a) The activity coefficients at infinite dilution for isopropanol and water are 11.825 and 2.986 respectively at 80°C and 1 atm. i) Calculate the van Laar Coefficients A12 and A21 [b]2. Relevant equation. A12=lnγ (1+((x2lnγ2)/( x1lnγ1))^2) The eqaution for A21 is the same...
23. ### How Does a Catalyst Affect Equilibrium Despite Different Activation Energies?

We are taught that adding a catalyst to an equilibrium system does not alter the position, just the rate of equilibrium attainment, because it increases the forward and backward rate by the same amount. Why and how can that be? The activation energies will be different for the forward and...
24. ### How Do You Calculate Kp and Qp for Chemical Reactions at Equilibrium?

Hey guys, I've just got an assessment coming up. I just want to double check if I got it right and perhaps people can help me with a question or two. QUESTION 1. Consider the reaction A(s) + 3B(g) = 4C(g), ΔH°=-16.6kJ i) Given Kc = 0.00570, calculate Kp at 198°C. ii) Given p(B) = 0.10atm...
25. ### Reequilibriation of a System Disturbed from Stable Equilibria

Hey. Somewhat of a strange, but possibly profitable question! I'm aware that a system that is at a stable equilibrium point will, upon a disturbance, return to that equilibrium. Consider the Earth's oceans, which is essentially a multicomponent homogeneous mixture, or a multicomponent...
26. ### Can a Dynamical System Have Multiple Locally Stable Equilibria?

Hi all Suppose for a dynamical system \dot x=f(x) , x \in \mathbb R^n there exists finite number of isolated equilibria, each of which is locally stable (i.e eigenvalues of the associated Jacobian have negative real parts). My question is: Can this happen for more than one equilibrium...
27. ### How Do You Calculate Kc and Kp for a Reversible Gas Reaction?

Homework Statement When 1.000 mol PCl5 is intorduced into a 5.000L container @500K, 78.50% of PCl5 dissociates to give equilibrium mixture PCl5, PCl3, Cl2 : PCl5--->PCl3+Cl2 (this eq. is reversible) (a) calculate Kc and Kp (b) if the initial concentrations are [PCl5]=.500M...
28. ### Phys. Chem. (Chemical Equilibria)

Homework Statement From Atkins Phys. Chem 9th Ed, Ex6.5a: Dinitrogen Tetroxide is 18.46% Dissociated at 25 deg Celcius and 1 bar in the equilibrium N2O4(g) <-> 2NO2(g). Calculate K (equilibrium concentration) at a)25 deg. C. b) 100 deg. C. given that ΔH(standard of reaction) = +56.2 kJmol^-1...
29. ### Ksp, saturated solutions and precipitation (Ionic Equilibria)

I have the following doubts while understanding the concept. Please help me solve them :- (1) What is a precipitate exactly? While determining the Ksp values, we say that there in a dynamic equilibrium between the solid undissolved solute in contact with the solution and the ions in solution...
30. ### Barium Chromate chemical equilibria

1. Recently did a lab experiment involving Barium Chromate. 1) When BaCl2 and K2CrO4 were mixed, I obtained a colourless solution and a yellow ppt was formed. This solution and ppt were split into 3 test tubes. 2) When HCl was added to tube 1, i got an observation that an orangey yellow...
31. ### Acid-Base Equilibria: Clarifying Confusion

While I am studying my Chemistry lecture notes, I find the following notes with which I am rather confused: For a particular acid and its conjugate base HA + H2O = H3O+ + A- Ka= [A-][H3O+] / [HA] A- + H2O = HA + OH- Kb=[HA][OH-]/[A-] KaKb = Kw pKw= pKa + pKb = 14 (at 298K) I am...
32. ### Advanced ICE Table (chemical equilibria)

Homework Statement Derive an expression for equilibrium concentrations in terms of formality f (and Keq) for the compounds in the the equilibrium reactions shown bellow. Homework Equations A2 + 2S <---> 2SA SA <---> S + A Where S is a substrate (THF) and A is an adduct (BH3)...
33. ### Where Can I Find Rigorous Solutions for Weak Acid-Weak Base Equilibria?

Such an equilibrium problem involves 3 equilibria: a weak acid, a weak base, and water autoionization. I find in various texts that several assumptions are made in dealing with this class of equilibria problems (ignore water's autoionization, conversion of the weak acid is on the order of...
34. ### What Does uo(g)=u1o(g) Imply in Chemical Potential Terms?

2 Phase Equilibria Confusion!? I am having trouble with the derivation for the chemical potential of liquid component of a system. We have a closed system with 2 components in their liquid and gas form This is the line that doesn't make sense to me: uo(g)=u1o(g) Isn't this saying that...
35. ### Chemistry - Equilibria questions involving ICE tables

In my book for all these equilibria questions involving ice tables when I end up with Ka = \frac{(x)(x)}{initial amount - x} they always say that if the Ka is tiny compared to the initial amounts then we can assume x will be too and we can omit as many x's as we like from this equation. This...
36. ### Which Salts Form Basic Solutions in Water?

Homework Statement OK so this is my first time actually posting but I have lurked around. I need help with two of my chemistry problems. Problem 1 Decide which one(s) of these answer choices are correct. A buffered solution is one which can be desribed by which of the following...
37. ### Solubility of a solid equilibria

I'm having some trouble understanding heterogenous equilibria. I read that solids, pure liquids and solvents are omitted from the equilibrium expression. Let's say I have some AgCl in a litre of water. The tiny amount of AgCl that dissociates and dissolved is given by its Ksp. I understand that...
38. ### Equilibrium Reactions: 2 Questions Explained

Hi, there have been two questions that have been bothering me and I would really like some explanations. 1. When an inert gas is added to an equilibrium reaction of gases. Why is there no change in equilibrium position? If an inert gas is added it doesn't react but increases total pressure of...
39. ### What is the First Condense Phase During Isothermal Compression?

Homework Statement I'm given vapor pressures of an assumed ideal gas: (Clausius Clapeyron.. ln(p) = -A/T-BlnT+C) I am given A, B, C for liquid and solid. And given T,melt. I am to find what the first condense phase is, and at what temperature, given isothermal compression from T>Tmelt...
40. ### How do different types of mixtures affect phase equilibria?

I am doing phase equilibria in college and I don't have very good books (I am in the first semester and I haven't got the chance to get good books yet) to study from and neither am I being able to find any websites that will explain to me the basic concepts of the chapter(wikipedia goes straight...
41. ### How Do You Calculate the Dissociation Constant (Ka) for a Weak Acid?

Ok, I'm having a hard time understanding the concept behind finding the dissociation constant. The question is: A 0.1 mol/L aqueous solution of weak monoprotic acid has a hydrogen ion concentration of 0.001 mol/L. The value of the ionization, Ka, for this acid is: a) 10-6 b) 10-2 c)...
42. ### Pressure and concentration equilibria

1. COCl2(g) D CO(g) + Cl2(g) Kp = 6.8 x 10-9 at 100oC What will be the equilibrium concentrations of all 3 gases if 1.0 atm of phosgene (COCl2) is placed into 5.0L reaction vessel? The answer is [COCl2]eq = 0.033M [CO]eq = [Cl2]eq = 2.69 x 10-10M I don't get how the second one...
43. ### Calculating Fraction of A Dissociated at 1000K with 1 atm and 10^-3 atm Pressure

Homework Statement The Equilibrium constant for A(g) -> 2B(g) is 1x10^-2 at 1000k. Calculate the fraction on A which is dissociated at 1000k if the total pressure is 1 atm 10^-3 atm Homework Equations PV=nRT B^2 / A = Ke (1x10^-2) The Attempt at a Solution for A...
44. ### Chemical Equilibria: Law of Mass Action & Beyond

chemical equilibrium law is made using the fundamental rule rate of forward reaction=rate of backward reaction and then applied law of mass action to it but law of mass action is not always correct in giving relation for the rate . so why it is used there? secondly if...
45. ### General Chemistry - Chemical Equilibria

General Chemistry -- Chemical Equilibria Suppose 1.22 atm of CH4(g), 2.57 atm of C2H6(g), and 15.00 atm of O2(g) are placed in a flask at a given temperature. The reactions are given below. CH4(g) + 2 O2(g) CO2(g) + 2 H2O(g) KP = 1.0x10^4 2 C2H6(g) + 7 O2(g) 4 CO2(g) + 6 H2O(g) KP = 1.0x10^8...
46. ### Equilibria analysis for Biomath Problem

Homework Statement Find all the positive equilibria for the system of the difference equations x(t+1) = \frac{ax(t)y(t)}{1+x(t)}; y(t+1) = \frac{bx(t)y(t)}{1+y(t)} a, b > 0. Then determine conditions on parameters so the equilibriums are locally asymptotically stable. Homework Equations An...
47. ### Chemistry How Do You Calculate Kp for the Formation of Ammonia from Nitrogen and Hydrogen?

Homework Statement The standard Gibb's free energy for the reaction N2+3H2<--->2NH3 is -33.0 KJ at 298 K. Everything is a gas. Calculate Kp for this reaction. Homework Equations I have in my notes that Keq=e^(-Delta G/RT) where R is the constant 0.008314 KJ/K. I also have a formula...
48. ### Acid/Base Equilibria (hard, i think).

Homework Statement 1 oz of 80% pure (NH4)2SO4, 1 gallon of water @ 25 degrees Celsius. 1 gallon = 3.785 L, 1 oz = 28.4 grams. Suppose an avid gardener prepares a solution by putting 1 oz of 80% pure Ammonium Sulfate in a gallon of water at 25 degrees C. a) what is concentration of...
49. ### Chemistry-acid base equilibria

p-Hydroxybenzoic acid, HOC6H4COOH, is a weak diprotic acid. A 25.00 mL aliquot of a dilute solution of HOC6H4COOH is titrated with a 0.0200 M NaOH solution. The first equivalence point was reached after 16.24 mL of the NaOH solution was added. a. If the values of the pH after 8.12 and 16.24 mL...
50. ### Bifurcation and Stability of Equilibria

When determining the stability of the equilibria (or, critical points) for our bifurcation diagrams, we have been shown to use phase line diagrams. I understand that if the function is moving away from the equilibria on either side than it is unstable, and i know that if the function is...