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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Why isn't Kw = ([H+][OH-]) / [H2O], when H2O is the reactant?

For the hypothetical reaction: $$ \ce{A <=> B + C}$$ the equilibrium constant expression is written as $$\ K= \frac{[\ce B][\ce C]}{[\ce A]} $$ So, why is $ K_\mathrm w $ written as: $$ K_\...
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Can the rate of reaction of a Voltaic/Galvanic cell be determined theoretically?

I am conducting a chemistry practical in which I measure the voltage of a Zn-Cu Voltaic cell over time. Assuming that the surface area of the electrodes are known, concentration of reactants are ...
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Why does an electron lose energy so that it falls back to a lower energy state than just stay at the higher energy state?

Suppose an electron in the 2nd shell gets excited and jumps to the 4th shell. Shouldn't the electron then exist in an unstable equilibrium in the 4th shell, than lose energy and drop down to the 2nd ...
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How does the initial starting temperature affect yield? [closed]

I am aware that using Le Chatelier's principle, increasing the temperature of a system (exothermic reaction) at equilibrium decreases yield as it causes a net reverse reaction. However, I would like ...
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What is the true meaning of Gibbs energy and chemical potential?

After doing some research and reading I found some problems which I will try to state as clearly as possible. The definition of Gibbs Free Energy says "the greatest amount of mechanical work which ...
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How can batteries reach equilibrium if the reactions are irreversible?

My book says that the batteries we have considered so far (Daniell cells) have a low life span because they reach equilibrium too quickly. In the next paragraph, it states they are also made by ...
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Does salt hydrolysis takes place in buffer solution? [closed]

I am a bit confused whether hydrolysis of salt takes place in buffer solutions because the books which I read doesnt consider them.But I think since weak base or weak acid salt is present hydrolysis ...
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Equilibrium pressure

Ammonium carbamate dissociates as follows: $$\ce{NH2COONH4(s)<=> 2NH3(g) + CO2(g)}$$ The value of $K_p$ for this reaction is found to be equal to $\pu{2.92 \times 10^-5 atm^3}$. If ...
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When pH > pKa and when pH < pKa and the effectiveness of buffer solutions

I understand that when $\mathrm{pH}= \mathrm{p}K_\mathrm{a}$, the buffer solution will be at its maximum capacity, and there will be equal concentrations of the acid/conjugate acid and the base/...
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Why does reducing the pressure in an equilibrium reaction favour the side with more moles of gas?

I was trying to explain it in terms of reaction rates and such; more than just 'Le Chatelier's principle states ...', but I can't figure out the underlying reason as to why. I can explain why for ...
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Equilibrium Constant & Rate-Determining Step

My first language is not English, so there might be some parts where it's hard to read. Sorry in advance. I have some questions regarding the derivation of the equilibrium constant and the rate-...
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Finding ionic radii from solubility data and density

$\pu{5.35 g}$ of a salt $\ce{ACl}$ is dissolved in $\pu{250 ml}$ of solution. The $\mathrm{pH}$ of the resultant solution was found to be $4.85.$ Find the ionic radius of $\ce{A+}$ and $\ce{Cl-}$ if ...
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Genuine confusion about the equilibrium constant [closed]

I gather that the equilibrium constant K = 1 implies that, at equilibrium, neither the forward nor the backward reactions are thermodynamically favoured. But if pressure of the system increases and ...
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Mathematical justification for Le Chatelier's principle

At equilibrium $$ \begin{align} K &= \exp\left(\cfrac{TΔS^\circ - ΔH^\circ}{RT}\right)\\ ⇒ \frac{\mathrm d \ln K}{\mathrm dT} &= \frac{ΔH^\circ}{RT^2} \end{align} $$ If enthalpy change is ...
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When is the concentration in which you put into the equilibrium constant equal to 1 for solids and liquids?

There are many websites which states that pure liquids and solids have a concentration equal to one, but for some equations they are not! How do you explain the difference for this equation? For the ...
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Chemical Equilibrium problem

I can't seem to get the answer that appears on the back of the book Here is what i did: a) $K_p=K_x p^{\Delta N}$; in this reaction $\Delta N =-1$, then $K_pp=K_x$ from $\Delta G=-RT\log K_p$ I ...
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Vapour pressure [duplicate]

I am confused. How does the change in volume of container affect the quantity of water, vapour and vapour pressure present in it(keeping the pressure of container constant)?
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How to confirm experimentally that a hemi-acetal compound has formed?

I have read that under mildly acidic or alkaline conditions alcohols can attack aldehydes/ketones to produce hemi-acetals. But the reaction is reversible, so the reactants and the hemia-cetal are in ...
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How do I find pH of a mixture of weak acids? [duplicate]

Suppose that we are given two weak bases $\ce{HA_1}$ and $\ce{HA_2}$. We are also given the $K_\ce{HA_1}$ and $K_\ce{HA_2}$. How can we calculate the $\mathrm{pH}$ of the mixture?
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Defining the position of equilibrium

I've read quite a few other answers on this site such as this one, but can't quite seem to understand fully yet. Say we have a container with gases reacting such that the number of moles on both ...
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Calculating thermodynamic quantities for hydrogenation of iron nitride

HW#6.3 If the reaction $$\ce{Fe2N(s) + 3/2 H2(g) <=> 2 Fe(s) + NH3(g)}$$ comes to an equilibrium at a total pressure of $\pu{1 bar},$ analysis of the gas shows that at $\pu{700 K}$ ...
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Chaos in chemical reactions

I recently read about Chaos Theory and was wondering if a chemical reaction results in or shows characteristics of chaos (I found a few examples of such reactions here) Chaos theory concerns ...
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Calculation of equilibrium constant in a gaseous system A ⇌ B + C

I am supposed to determine whether the following two statements are true or false: For the reaction $\ce{A (g) <=> B (g) + C(g)}$, $K_p = \pu{1 atm}$. If we start with equal moles of all ...
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Liquid solutions and vapour pressure

"The vapour pressure of water at 80° C is 355 torr. A 100 mL vessel contained water-saturated oxygen at 80° C, the total gas pressure being 760 torr. The contents of the vessel were pumped into a 50 ...
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Why are the equilibrium exponents stoichiometric when the rate law's are not? [duplicate]

I'm learning about rate law and equilibrium, and the textbook really hammers in that the exponents for the rate law must be determined experimentally - you can't just use the coefficients from the ...
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What is meant by pure solids or pure liquids? [duplicate]

In by book, under the topic Heterogeneous Equilibrium it is given For pure solid and pure liquid, active mass is taken to be unity, i.e., 1 as they remain constant throughout the reaction. Could ...
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Ce₂(SO₄)₃ solubility in water [duplicate]

I have mostly come across examples of solids whose solubility increases in liquids with an increase in temperature. However, there seem to be exceptions to generalized rule this such as the solubility ...
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How can I calculate the equilibrium constant for this reaction?

Silver(II) oxide partially decomposes into solid silver and oxygen gas according to: $$\ce{2 AgO(s) <=> 4 Ag(s) + O2(g)}$$ with enthalpy $H^\circ = \pu{62.0 kJ}$ and entropy $S^\circ = ...
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Understanding the solubility of Ca(HCO3)2

According to wikipedia Ca(HCO3)2 has the following solubility values: 16.1 g/100 mL (0 °C) 16.6 g/100 mL (20 °C) 18.4 g/100 mL (100 °C) So I assume Ca(HCO3)2 would precipitate beyond this level. ...
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$K_c$ vs $K$ in equilibrium reactions

I don’t understand why the following question The decomposition of nitrosyl bromide $(\ce{NOBr})$ proceeds by the following reaction: $$\ce{2 NOBr(g) <=> 2 NO(g) + Br2(g)} \qquad K = 0....
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Reversibility of a reaction

I was doing some questions on equilbrium. I got stuck in this particular question. Identify which of the following reactions are reversible. $$ \begin{align} \ce{Fe + S &-> FeS }\label{...
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Book reference for chemical equilibriums [duplicate]

I need to practice more chemistry equilibrium questions but most of the books contain only theory parts and not enough questions. so can please recommend me a question book.
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Same Activation Energy for Forward and Backward Reactions

While reading about equilibrium, I read that the equilibrium constant, $K_\mathrm{c}$, changes with temperature due to the forward and backward reactions having different activation energies. Is it ...
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Can precipitation reactions attain equilibrium?

While studying about the characteristics of Chemical Equilibrium, I came across a point in my book which read A chemical equilibrium can be established only if none of the products is allowed to ...
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Is the equilibrium constant calculation only applicable to homogeneous reactions?

In my text book, it states the general formula for the equilibrium constant is: Then it states that "The equilibrium constant expressions described here apply to homogeneous reactions." Does this ...
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Calculating Equilibrium Constant from Cell Potential at Nonstandard Temperature

I'm currently working on a problem for a general chemistry class. This is the voltaic cell given in the problem: $$\ce{Sn^4+(aq) + Cu(s) -> Sn^2+(aq) + Cu^2+(aq)}$$ $$E^\circ_{cell} = \pu{-0.21 V}$$...
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Why doesn't the solute settle out of a solution, such as brine or sugar water? [closed]

If I have a solution of salt or sugar dissolved in water, the solute will never settle out or "fall to the bottom", no matter low long I wait. Why is that? Since salt and sugar (in their pure, solid ...
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How would I find the molarity/concentration of a gas using pV = nRT?

The problem I'm working on is: At $\pu{1100 K}$ and a total pressure of $\pu{1 atm}$, $\ce{SO3}$ is $75.0\%$ dissociated. $$\ce{2SO3(g) <=> 2SO2(g) + O2(g)}$$ Assume $\pu{1.00 mol}$...
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What would be the concentration of products in this calcium producing system?

I wanted to figure out a way to make calcium metal with potassium oxide. $\ce{K2O}$ undergoes disproportionation at $\pu{350-430 °C}:$ $$\ce{2 K2O -> K2O2 + 2 K}$$ Now, if I mixed in $\ce{CaO}$ (...
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Is it possible to have only liquid in a closed container?

I recently read an answer by Aman Rusia for this question: Is a liquid in a container always in equilibrium with its vapour? In it, they say that You can't have a container filled with only ...
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Calculating partial pressure equilibrium constant Kₚ given initial pressure and equilibrium pressure

A reaction $$\ce{A(g) <=> B(g) + C(g)}$$ happens in constant volume and constant temperature. The reaction starts only with gas $\ce{A}$ (no $\ce{B}$ or $\ce{C}$) with given pressure $...
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Why is the equilibrium constant unitless?

I read that the equilibrium constant is unitless because the molar activities of each of the species are used in the equilibrium expression, not the actual concentrations themselves. I understand that....
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Is “mass-action ratio” identical to “reaction quotient?”

Mass-action ratio Reaction quotient According to their definitions expressed in the above Wikipedia articles, these two concepts seem to be totally identical. Is that true? If not, what is the ...
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How can I calculate the equilibrium between several reactions?

If I mix xNaOH + yCdCl2 + zZnCl2 in an aqueous medium, how can I calculate the final equilibrium quantities of the resulting salts (which I suppose may be the following): Q1 NaOH Q2 CdCl2 Q3 ZnCl2 Q4 ...
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Equivalents Triethylamine in Swern-oxidation

Hey folks, so I've been wondering why the use of 5 equivalents of Et3N in this case of a Swern-oxidation is necessary. I have done this reaction succesfully quite a few times now, but all the ...
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Are there any exceptions to Le Chatelier’s principle? [duplicate]

Peter Atkins says In introductory chemistry, we meet the empirical rule of thumb known as Le Chatelier’s principle: When a system at equilibrium is subjected to a disturbance, the ...
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Finding the temperature at which the system reaches equilibrium

I’m really stuck on this problem. This involves dissolving Borax: $$\ce{Na2B4O7•10H2O(s)<=>2Na^+(aq) + B4O7^2-(aq) + 10H2O}$$ $$\begin{align}\Delta H&=\pu{109 kJ/mol} \\ \Delta S&= \pu{...
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Changing conditions of gaseous mixture

A gaseous mixture of $\ce{NO2}$ and $\ce{N2O4}$ is sealed in 4 identical vessels with movable pistons. When the conditions are modified as described in 1) to 4), in which condition does the molar ...
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Shift of Equilibrium

A friend of mine stumbled upon this question while revising equilibrium. Apparently the answer is A. The answer obviously cannot include adding a catalyst. Furthermore, according to le Chatelier's ...
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What does it mean for chemical reaction network to be in equilibrium?

What does being in "equilibrium" mean for a set of chemical reactions? If we have some number $n$ of $\ce{A}$ molecules and $m$ of $\ce{B},$ and the following reaction where $\ce{A}$ and $\ce{B}$ can ...