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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64 views

Drug pH and pKa known, is it an acid or a base? [closed]

I want to answer the question if a drug which is analysed for pH and pKa is ionised or not ionised in a cow stomach with a pH of 6. The drug has a pH of 8,52 and a pKa of 8,78. Since the pH is 8,52 ...
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109 views

Intuition for why catalyst affects both forward and reverse reactions equally?

I have looked for quite a long time on the site however all the answers involve mathematical explanations involving Arrhenius's equation. I would really like an intuitive reason (or one using ...
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60 views

Effect of solid in equilibrium

CaCO3 (s) = CaO (s) + CO2 (g) We know that pure solids quantity doesn't affect the position of equilibrium. But the application of pressure in gas does. If we add CaCO3 in the closed system, the ...
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1answer
212 views

How does monoethanolamine (MEA) increase pH?

I know pH of a solution increases with increase concentration of $\ce{OH-}$. I'm wondering: when adding MEA, is the $\ce{OH-}$ group from the MEA breaking off, or is it the whole MEA molecule taking ...
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4answers
658 views

Why does the degree of dissociation change when we dilute a weak acid even though the equilibrium constant $K$ is constant?

$K$ represents the ratio of concentrations of molecules in a solution at equilibrium, which means that $Q_\mathrm{r}$ (that ratio at any given point) looks to be identical to $K$. In other words, the ...
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1answer
630 views

Calculating Equilibrium Partial Pressures Given Kp and Mass

For the reaction $$\ce{AsCl5(g) <=> AsCl3(g) + Cl2(g)}$$ at $550$ K, the equilibrium constant ($K_p$) is $9.81$. Suppose that $3.150 \ g$ $\ce{AsCl5}$ is placed in an evacuated $600$ ml ...
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2answers
211 views

How can you use ICE tables to solve multiple coupled equilibria?

If I have a problem involving multiple coupled equilibrium reactions, such as Calcium fluoride, $\ce{CaF2}$, has a molar solubility of $\pu{2.1e−4 mol L−1}$ at pH = 7.00. By what factor does its ...
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2answers
110 views

Equilibrium constant for complex cobalt ion

What is the equilibrium constant for the $\ce{Co(H2O)_6^{2+}(aq) + 4 Cl-(aq) <=> CoCl_4^{2-}(aq) + 6H2O(l)}$? I've looked at various sources but none seem to yield the actual equilibrium ...
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1answer
156 views

Determining the reduction potential of a half cell reaction at a given pH

$E^\circ_\ce{Cu^2+|Cu} = \pu{0.34 V}$. What will be reduction potential at $\mathrm{pH} = 14$ for the same couple? Given that $K_\mathrm{sp}$ of $\ce{Cu(OH)2}$ is $10^{-19}$. My Attempt I think ...
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1answer
94 views

Decrease of volume by half in equilibrium - with specific numbers- how to solve?

$$\ce{CO (g) + Cl2(g)<=>COCl2}(g)$$ We have 2 mols of $\ce{CO}$, 1 Mol of $\ce{Cl2}$,and 9.765 Mols of $\ce{COCl2}$ contained in 1 L. The system is currently in equilibrium. We ...
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407 views

Is liquid water in equilibrium with water vapor at room temperature?

This question was inspired by Why does liquid water form when we exhale on a mirror?. This question is different from Why does water evaporate at room temperature? because it asks about whether an ...
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Is there a difference between equilibrium and steady state?

The term equilibrium is used in the context of reversible reactions that reach a point where concentrations no longer change. The term steady-state is used in enzyme kinetics when the concentration of ...
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85 views

Why can't a weaker acid protonate the conjugate base of a stronger acid?

So I've heard that, supposedly, a weaker acid cannot protonate the conjugate base of a stronger acid to give that stronger acid. For instance, adding ethanoic acid to sodium sulphate will not result ...
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110 views

Is common ion effect applicable on two strong electrolytes

Consider the nitration of benzene using mixed conc. $\ce{H2SO4}$ and $\ce{HNO3}$.If a large amount of $\ce{KHSO4}$ is added to the mixture the rate of nitration will be : Faster Slower ...
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143 views

Determination of pKb of a mono acidic base

$20$ mL of a weak monoacidic base($\text{BOH}$) requires $12$ mL of $0.3$ M $\text{HCl}$ solution for the equivalence point. During titration, the pH of the base solution was $10$ upon the addition of ...
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2answers
204 views

Can we combine two reactions and then calculate the equilibrium concentrations?

At a certain temperature, $\ce{N2O5}$ dissociates as: \begin{align} \ce{N2O5 (g) &<=> N2O3 (g) + O2 (g)} & K_1 &= 4.5 \end{align} At the same time, $\ce{N2O3}$ also dissociates ...
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253 views

Calculate pH of a buffer solution

Calculate the pH in a buffer prepared from $\pu{50 mL, 0.30 M}$ formic acid ($\ce{HCOOH}$) and $\pu{30 mL, 0.40 M}$ sodium formate ($\ce{HCOONa}$). My way of solving: $n_{\ce{HCOOH}} = 0.05 \times ...
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1answer
268 views

Q. 36 2018 molar solubility of CaF2 at pH3 given molar solubility at pH7 and pKa of HF [closed]

This is Q36 on the 2018 Chemistry Olympiad: Calcium fluoride, $\ce{CaF2}$, has a molar solubility of $\pu{2.1e–4 mol L–1}$ at pH = 7.00. By what factor does its molar solubility increase in a ...
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How can the ocean act as a buffer?

I was reading up on the buffering effect of the ocean and I was quite confused about how the buffer is able to do anything. The buffer I will refer to is below: $$\ce{CO3^{-2} +H2O <=> HCO3 + OH^...
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846 views

Why proton concentration is divided by 10⁻⁷?

I am reviewing the book Biochemistry Concepts and Connections by Appling, Cahill, and Mathews and I cannot understand why they divide by the hydrogen concentration by $10^{-7}$. Why not just leave it ...
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Defining the partial pressure equilibrium concentration

First off, I am not a chemist. I'm an engineer with an interest in thermodynamics for engine simulation for the basis of emissions. So if I have asked something stupid, this will be why. So I am ...
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287 views

What does the reaction of hydrogen and iodine to hydrogen iodide look like?

The reaction, $\ce{H2 + I2 <=> HI}$ is often used as an example for equilibrium reactions. It is however a difficult reaction to show in a school laboratory: we are not equipped to work with ...
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Error with explaination of shape of weak acid strong base titration?

I have read the other posts on the same question posted on chemistry exchange such as this one: Shape of Weak-Strong Acid-Base Titration and here : What does the small, steep curve at the very ...
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1answer
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Determining reaction order in equilibrium reactions [closed]

Am hoping that someone can help me with the below question, and that I am asking in the right place. Am new here, so please forgive any missteps. Given a reaction like this: $$\ce{A + B <=> C +...
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Distribution coeffecient without concentrations

From what I understand about distribution coefficient is straight from my book — which does not give any practice examples — is that $$D = \frac{C_\mathrm{A}(\text{ext})}{C_\mathrm{A}(\text{orig})}$$ ...
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Using Le Chatelier's Principle [duplicate]

The following reaction is allowed to reach equilibrium. $$\text{CoBr}_2(g)\rightleftarrows\text{CO}(g)+\text{Br}_2(g)$$ What happens to the reaction when inert argon gas, $\text{Ar}(g)$, is added? ...
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1answer
690 views

Pressure at which graphite and diamond are in equilibrium

I came across this problem : The standard state Gibbs free energies of formation of C(graphite) and C(diamond) at $T = \pu{298 K}$ are $\pu{0 kJ mol-1}$ and $\pu{2.9 kJ mol-1}$, respectively. ...
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1answer
518 views

Equilibrium constant for the neutralization of weak acid by strong base

Acetic acid has a $K_\mathrm{a}$ of $\pu{1.8e-5}$. What is the equilibrium constant for the neutralization of this acid with $\ce{NaOH}$? Given acetic acid $$\ce{HC2H3O2 + H2O <=> C2H3O2- + ...
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339 views

Effect of temperature on equilibrium constant in terms of entropy change

This question was asked in the JEE examination of 2017 : [A] option is incorrect since the system is losing heat and hence $$ \Delta S = -ve$$ [B] Lets assume we have an endothermic reaction $$\...
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39 views

Equilibrium - Pressure Vs. Concentration [closed]

Does increasing the pressure increase the concentration of reactants as well? If: $$\ce{A(g) + B(g)<=>C(g) + D(g)}$$ Assuming all reactants and products are gases. According to Le Chatelier'...
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97 views

How is preparing a buffer possible?

I understand the concept of an equilibrium buffer solution, however I am a bit hung on how creating it doesn't shift the weak acid equilibrium. $$\ce{CH3COOH + H2O <=> CH3COO- + H3O+}$$ $$ K_\...
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2answers
584 views

Calculating solubility of iron(III) hydroxide in water

The following example in Skoog's Analytical Chemistry uses mass-balance and charge-balance equations to calculate the solubility of iron(III) hydroxide in aqueous solution. $$ \begin{align} \ce{Fe(...
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130 views

Does ammonium react with water in an ammonia solution?

In the following equilibrium: $$\ce{NH3 + H2O <=> NH4+ + OH-}$$ Is it possible for the ammonium to simultaneously establish another reaction with water? $$\ce{NH4+ + H2O <=> NH3 + H3O+}$...
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Existence of single ion activities

I have used Davies equation to find what I believed was single ion activities and multiplied them on concentrations to define the thermodynamic dissociation constants for any kind of buffer to find ...
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98 views

What happens when chemical equilibrium is restored after being disturbed?

I'm aware that, according to Le Chatelier's principle, a reaction will shift its equilibrium position in order to counteract the disturbance at equilibrium. However, I don't know what that means after ...
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115 views

Molarity and equilibrium reactions Kc [closed]

Samples of $\ce{A}$ ($\pu{1.40 mol}$) and $\ce{B}$ ($\pu{0.80 mol}$) are placed in a $\pu{2.0 L}$ container and the following reaction takes place: $$\ce{2 A (g) + B (g) <=> C (g) + D (g)}$...
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3answers
306 views

pH of 0.05 M NaH2PO3

What is the pH of a $\pu{0.050 M}$ solution of $\ce{NaH2PO3}$? I am given that $\mathrm{p}K_\mathrm{a1} = 2.0$ and $\mathrm{p}K_\mathrm{a2} = 6.58$. I am getting two different answers, $3.94$ and $4....
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342 views

H2O and Le Châtelier’s principle [duplicate]

According to Le Châtelier’s principle, the adding of a reactant causes a shift in the direction of products, to minimize the modification. But what about $\ce{H2O}$? When can it be considered as a ...
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1answer
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Acidity of carbonate ions creates paradox?

Whilst I understand why salts can be acidic or basic, the carbonate reaction confuses me (carbonate being a basic ion). $$\mathrm{{CO_3}^{2-} + H_2O \ce{<=>} {HCO_3}^- + OH^-} \\ \mathrm{{...
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Why doesn't chemical equilibrium lead to uncertainties?

Let's consider a reaction $$\ce{a A + b B <=> c C + d D}$$ We will also assume that the concentrations are low and the activity coefficient is one. Now let's say initially one has $p_0$, $q_0$,...
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What would be different about a heavy-water ocean world?

The water on Earth is primarily made of $\ce{H2O}$. I'm wondering about the conditions in a hypothetical $\ce{D2O}$ ocean world. Would it be stable over geologic timescales (~$\pu{0.1–2 Ga}$)? What ...
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Which rate, the forward or reverse rate of acid dissociation, is more strongly affected when diluting acetic acid in aqueous solution?

Acetic acid is a weak acid. It is in equilibrium with acetate and hydronium ions in aqueous solution: $$\ce{CH3COOH(aq) + H2O(l) <=> CH3COO-(aq) + H3O+(aq)}$$ Ostwald's law states that the ...
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89 views

Why degree of dissociation/ionisation affected by dilution? [closed]

What happens when we dilute, say, an acid which is weak, and then add water to it? What motivates or pushes it to dissociate more? We are just adding some molecules of water, right? So, what exactly ...
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1answer
81 views

How to calculate the standard Gibbs energy at equilibrium?

Given that $K_c = 1.7 \times 10^{-13}$, calculate $\Delta G^{\circ}$ for this equilibrium mixture at $\pu{298 K}$. $$\ce{N2O (g) + \frac{1}{2}O2 (g) <=> 2 NO (g)}$$ I've calculated: $$ \...
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232 views

Whats the difference between reversible process in thermodynamics and reversible chemical reactions?

We know that in thermodynamics, reversible process never occur since entropy should be conserved. However, in chemistry we do have a lot of reversed chemical reactions that forms reactants from ...
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Can equilibrium be calculated at any time of an acid base reaction and still be the same? [closed]

Should the equilibrium constant $K$ be calculated at the end of an acid-base titration or can we calculate it in the middle of the titration for example? If so, will the calculated equilibrium ...
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37 views

Calculating the amount of a product at the reaction equilibrium

$\ce{Cr2O3}$ can be reduced to the elements chromium with high temperature and carbon by this two reactions: $$ \begin{align} \ce{Cr2O3(s) + 3C(s) &-> 2Cr(s) + 3 CO(g)} \label{rxn:1}\tag{1}\\ \...
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Determining the equilibrium constant

This is freely translated, I hope it's not too bad. The reaction to dehydrate methylcyclohexane to toluene in the gaseous phase: Formulate the reaction equilibrium's constant. Now, that'...
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419 views

Gibbs free energy ΔG=ΔG°+RTln(Kp) different expressions for ΔG

ΔG=ΔG°+RTln(Kp) If I understand it correctly, the ΔG in this equation gives the "distance" in Gibbs free energy of a chemical system at a particular moment in a reaction (encoded by the Kp) to the ...
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Equilibrium constant vs Equilibrium position [duplicate]

In my book, a statement is written as: " Kc is Equilibrium constant and has a constant value at a particular temperature Whereas the ratio of products to reactants is described as the position of ...