Questions tagged [equilibrium]

The state in which both reactants and products are present at concentrations which have no further tendency to change with time.

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For reactions proceeding towards dynamic equilibrium, why does the rate of forward reaction decrease with time?

When I asked my teacher this question, she said that it was because the concentrations of the reactants would decrease and thus since rate = -d[reactant]/dt, rate would decrease. However, when the ...
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why does the partial pressure not change? [closed]

Suppose I have the equilibrium in a closed container at constant temperature: $$\ce{2CaSO4(s) -> 2CaO(s) + 2SO2(g) + O2(g)}$$ If the volume of the container is halved, the reaction should move ...
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Thermodynamics of chemical reactions “at constant pressure”

Chemical reactions occur at constant temperature and pressure. Consider a gaseous, equilibrium reaction: $\ce{2NO2(g) <=> N2O4(g)}$. Most questions/textbooks formulate such questions by stating:...
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Rate law expressions [closed]

Question For the reaction, $$\ce{2NO(g) + 2H2(g) -> N2(g) + 2H2O(g)}$$ The rate expression can be written in the following ways: $\frac{\mathrm{d}[\ce{N2]}}{\mathrm{dt}} = \mathrm{k_1}[\ce{NO}][\...
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Equilibrium constants and concentrations [closed]

I know that concentrations of pure solids and liquids must be ignored in equilibrium constant expression, as they are constant. However in this reaction, they have taken the concentration of compound ...
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Effect of adding an acid or base to water with respect to concentration of ions

So I know that there's auto-ionization of water according to: $$\ce{2H2O <=> H3O+ +OH-} \tag{1}$$ If I have pure water where the concentrations of both $\ce{H3O+}$ and $\ce{OH-}$ is $10^{-7}$ ...
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Effect on mass when decreasing pressure in equilibrium reaction

For example, if we have the reaction: $$\ce{A + B <=> C}$$ And the volume is decreased, the pressure would increase. Hence, according to Le chatelier's principle, the system will partially ...
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How is the formula of mean activity coefficient derived?

The mean activity coefficient is defiend as follows: $$\gamma_\pm = (\gamma_+\gamma_-)^{1/2}.\tag{1}$$ If Debye-Hückel equation $$-\log\gamma_i = 0.5z_i^2\mu^{1/2}\tag{2}$$ is used, then the mean ...
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Equilibrium between hydroxides and ketones/aldehydes

In the reaction between hydroxides and ketones/aldehydes, an equilibrium will be established between the tetrahedral intermediate and the reactants. For aldehydes, significant amounts of the ...
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Equilibrium constant for heterogeneous equilibria having aqueous as well as gaseous reactants

Suppose we have a heterogenous equilibrium : $$\ce{A(aq) +B(aq) <=> C(g) +D(aq)}$$ Which equilibrium constant is used here? Both pressure and concentration terms are there. So, according to me, ...
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Equilibrium Constants for Diatomic Gases at High Temperatures

I'm new here and I haven't taken chemistry beyond high school, so please forgive the ignorance. I am reading a book about hypersonic aerodynamics, and I am trying to connect some chemistry knowledge ...
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Reducing pressure and calculation of concentrations at equilibrium

For the equilibrium $$\ce{PCl5(g) <=> PCl3(g) + Cl2(g)}$$ $$ K_c = \pu{4.16E-2 mol dm^{-3}}~\text{at}~\pu{250 °C}$$ $$[\ce{PCl3}] = [\ce{Cl2}] = \pu{0.204 mol dm^{-3}}$$ If the pressure of ...
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Why does Le Chatelier's principle work for temperature changes? [duplicate]

I do science tutoring. One of my students asked me why Le Chatelier's principle works, and I was able to explain it for concentration and pressure by referencing the law of mass action, but I could ...
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An expression for equilibrium constant of isotope reaction

Consider the isotope exchange reaction: $$\ce{C ^{16}O + 1/2 ^{18}O {}^{18}O <=> C^{18}O + 1/2 ^{16}O^{16}O}$$ The equilibrium constant for the reaction is: $$K=\frac{\prod (a_i)^{n_i}_{products}...
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Equilibrium constants [duplicate]

Being the relation between Kc and Kp: Kp=Kc(RT)^Δn It's clear that their values are different (unless Δn=0), so... Which value should I use in order to calculate ΔGº, since obviously the standard ...
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Dissolution of iron(III) hydroxide

Problem From the theoretical tour of the Mendeleev Olympiad in Chemistry: a) Calculate the minimal amount of sulfuric acid that should be diluted with water to yield $\pu{100 mL}$ of solution that ...
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A Thermodynamics question involving the molar solubility and Ksp of CaCO3

This thermodynamics question is from my textbook, I am not sure how to solve it correctly and I do not have the answer. The first thing I did was to calculate the number of moles from the Ca(OH)2 ...
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Can there still exist equilibrium with a very high equilibrium constant?

Problem Consider the reaction translated by: $$\ce{2 CO(g) + O2(g) <=> 2 CO2(g)} \quad K_c = 2 \times 10^{22}~\text{at } \pu{1000 K}$$ The order of magnitude of the equilibrium constant, $K_c$,...
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An equilibrium question involving mixing equal volumes of HCl and H2SO4

Question: Calculate the concentrations of H3O(+) and SO4(2-) in a solution prepared by mixing equal volumes of 0.2M HCl and 0.6M H2SO4. (Ka1 for H2SO4 is very large, and Ka2 for H2SO4 is 1.2E-2) Here ...
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Changing pressure on equilibrium

Recently I heard my teacher say that when increasing the total pressure of the system, the reaction which is "more dependent on collisions" is favoured. This seems to make sense, although I'...
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How can I analytically calculate the rate of thermal decomposition of calcium carbonate?

I am a first-time poster on Chemistry StackExchange, and not much of a chemist. I'm trying to determine the rate of thermal decomposition (in mol/s) of calcium carbonate ($\ce{CaCO3}$) at various ...
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86 views

Which make HCO3- to show two pH values at two scenarios?

According to the below two titrations, Image Reference: https://chem.libretexts.org/Bookshelves/General_Chemistry/Book%3A_Chem1_(Lower)/13%3A_Acid-Base_Equilibria/13.05%3A_Acid%2F%2FBase_Titration If ...
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Why can’t I use solubility product for normally soluble compounds?

Solubility product only applies to sparing soluble ionic compounds (chemguide) I read this in a website. But I don’t see what this should be the case. Taking $\ce{NaCl}$ for example, there’s an ...
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Reversibiliy and equilibrium

My textbook states "A system is in thermodynamic equilibrium if it is in Thermal, Mechanical, and chemical equilibrium simultaneously". The Wikipedia article on "reversible processes&...
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Can the degree of dissociation of a weak acid be more than 1?

My common sense dictates that it can't be more than 1 because after all it is the number of moles dissociating per mole of a substance. But I was reading about Ostwald's law of dilution and came ...
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Why isn't the chemistry of a zinc-air battery (meaningfully) hindered by an activation energy barrier?

Virtually every source I've read pertaining to zinc-air batteries explain the chemistry of it either using these formulae or a simplified version of them: $$ \begin{align} &\text{Anode:} &\...
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Activity of a chemical species and compound

While reading a book on Instrumental analysis by Skoog, in appendix part they explain activity of a species. The relationship between activity of a species and it's molar concentration $[X]$ is given ...
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Is entropy maximum in equilibrium?

Usually, in the context of non-equilibrium thermodynamics, it is said that entropy achieves a maximum in equilibrium, so the Taylor series expansion of entropy around the equilibrium state as a ...
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How many grams of sodium phosphate must be added to precipitate as much of one ion as possible?

Problem text: Solid sodium phosphate is slowly added to $\pu{200 mL}$ of a solution containing $\pu{0.002 mol}$ of aluminum chloride and $\pu{0.001 mol}$ of calcium chloride (assuming no volume ...
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Why does a first order reaction only depend on the concentration of a single reactant?

I am new to kinetics so please explain it from basic, If there is a reaction - $$\ce{A + B + C -> D}$$ In first order reaction rate is given by- $\mathrm R = k[\mathrm A]$ or $\mathrm R = k[\...
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Is pK_{In} = pH at equivalence point still true for weak basic organic indicators?

I am reading Ostwald Theory of Titration which says that indicators are organic weak acids or bases. To prove the relation that $\mathrm{p}K_\mathrm{In} = \mathrm{pH}$, the textbook uses the following ...
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Latent Heat, Vapor pressure and Equilibrium [duplicate]

So after reading about this topic i wanted to share what i learned and i wanted you guys to tell me if what i am writting is correct: A pressure vessel has propane inside and it is pressurized. The ...
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Measuring vapour pressure in a closed system

My experiment requires the determination of vapour pressure from which I will calculate the number density (or number of moles of the molecule) later, for a closed system. Here's my setup : Liquid ...
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2answers
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Van 't Hoff equation

In thermodynamics many definition has been made from partial derivatives at constant conditions for instance: Let $U$ be $U:f(S,V,m_𝑘)$ then: $$T = \left( \frac{\partial U}{\partial S} \right)_{V, m_{...
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Does the first step in electrophilic aromatic substitution follow equilibrium? If so, can equilibrium constant be calculated?

Using chlorine (a Lewis base) and ferric chloride (a Lewis base) as an example, the first step I saw in the textbook looks like this: The picture above depicts the Step 1 in the EAS mechanism using ...
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Finding initial amount of ammonia using equilibrium constant and amount of nitrogen gas

Question When an amount ammonia is added at $\pu{600 K}$ in a $\pu{1 L}$ container the following reaction takes place: $$\ce{N2(g) + 3 H2(g) <=> 2 NH3(g)}$$ The equilibrium constant $K_c = 4.20$...
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Reaction of hydrogen peroxide with sodium carbonate [closed]

In my book the following acid base reaction is written: $$\ce{H2O2 + Na2CO3 -> Na2O2 + H2O + CO2}$$ But I found that the $\mathrm{p}K_\mathrm{a}$ value of $\ce{H2CO3}$ is less than the one for $\...
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How to calculate mass of calcium fluoride that will dissolve in sodium fluoride solution?

The solubility product of calcium fluoride, $\ce{CaF2},$ is $\pu{1.46E-10 mol^3 dm^{-9}.}$ What mass of calcium fluoride will dissolve in $\pu{500 cm^3}$ of $\pu{0.10 mol dm^{-3}}$ sodium fluoride ...
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Need help finding equilibrium constant for equilibrium system [closed]

The reaction between iron (III) ions and thiocyanate ions, SCN$^-$, is an equilibrium reaction: Fe$^{3+}$ (aq) $+$ SCN$^-$ (aq) $\ce{<=>}$ FeSCN$^{2+}$ (aq) When $20$cm$^3$ of $1.0\times10^{-3}$ ...
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Why is chromate stable in basic medium and dichromate stable in acidic medium?

When I was studying the equilibrium existing between chromate and dichromate ions in the solution, I came to know that Chromate ion is more stable in basic medium while dichromate ion is stable in ...
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Vapor Pressure and Boiling Point [duplicate]

I heard that the boiling point of a solution is the temperature where its vapor pressure at that temperature equals the atmospheric pressure at that temperature. Thus at higher altitudes, as the ...
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Why are pressure or volume not able to change the equilibrium constant? [duplicate]

It is stated in my textbook that temperature is the only factor that can change the equilibrium constant. According to the Ideal Gas Law, temperature is dependent on the pressure and volume. Thus, ...
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Chemical Equilibrium - Le Chatelier's principle

If the concentration of reactants is increased such that one is a limiting agent, wouldn't the concentration of products also increase (because excess of a reactant will get carried to the other(...
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Equilibrium involving both gas phase and aqueous phase

If I have been given an equation that involves a gas-aqueous phase equilibria, how do I write the equilibrium constant? I have come across several questions that give equations having BOTH gas and ...
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Are all dynamic equilibrium reactions with neutralization, must also be buffers?

Reactions like: $\ce{H2CO3_{(aq)} + H2O_{(l)} <--> H3O+_{(aq)} + HCO3-_{(aq)}}$ or $\ce{C5H5N_{(aq)} + H2O_{(l)} <--> C5H5NH+_{(aq)} + OH-_{(aq)}}$ Does that mean that the last stage ...
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Does an increase in pressure always causes increase in molar concentration of each gaseous substance involved?

Question Statement : "An increase in pressure (caused by decrease im volume) at equilibrium results in increase in molar concentration of each gaseous susbstance involved" This statement is given ...
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Calculation of Degree of Dissociation from Ostwald's Dilution Law

A "weak" electrolyte, $\ce{A+B-}$, ionizes in solution as: $$\ce{AB <=> A+ + B-}\tag{1}$$ $$ K_d =\dfrac{\ce{[A+][B-]}}{\ce{[AB]}}=\dfrac{(\alpha c_{0})(\alpha c_{0})}{(1-\alpha )c_{0}}=\...
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Calculating the pH of a sodium phosphate solution [closed]

I have the following question in a chemistry homework: Calculate the $\mathrm{pH}$ of a solution made by dissolving $\pu{113 g}$ of sodium phosphate in enough water to make a solution with a final ...
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Defintion of Solubility in Different cases

How do we define solubility (in moles per liter) in cases when concentration of cation is not equal to the concentration of anion? e.g. When we put AgCN in an acidic solution (Leading to formation of ...
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Entropy and Equilibrium Constant: Chemical Thermodynamics

For a reaction taking place in a container in equilibrium with its surroundings, the effect of temperature on its equilibrium constant $K$ in terms of change in entropy is described by: (A) With the ...

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