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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38 views

Effect of amount of substance on equilibria

Considering the two equilibriums below, when the $[\ce{H+}]$ decreases, my book says that equilibrium \eqref{rxn:2} will shift to the left by a greater extent compared to equilibrium \eqref{rxn:1} ...
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What is the correct expression for ionization constant of water?

I have seen two different formulas for ionization constant of water in two different books: $$ \begin{align} K_\mathrm{eq} &= \frac{a(\ce{H3O+})\cdot a(\ce{OH-})}{a(\ce{H2O})^2}\tag{1}\\ K_\mathrm{...
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Precipitation Titration Question [closed]

This was a multiple choice question: A student wishes to determine the concentration of a lead solution, using a precipitation titration. The student takes a 25.00 ml aliquot of the lead solution and ...
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The effect of changing the pressure on an equilibrium

I was reading the section on Le Chatelier's principle (section 6.8) from Chemical Principles by Steven S. Zumdahl. On page 191 where I'm currently at, I do not understand why, to consider pressure ...
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How do the assumptions of the Nernst equation impact its accuracy?

I was just wondering what impact the assumption that the equilibrium membrane potential for an ion is dependent on just the ion itself (if it is the only thing that is permeable). For instance, if I ...
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How will the addition of water affect equilibrium in the following reaction? [closed]

2Al(s) + 2NaOH(aq) + 6H2O(l) ⇆ 2NaAl(OH)4(aq) + 3H2(g) What characteristic does the reaction need to have in order to favor hydrogen production when temperature is increased?
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Calculating pH of weak acid considering hydronium ions from water

In general to calculate pH of a weak acid , if we have $c$ concentration of acid initially then at equilibrium $\ce{H3O+}$ concentration is said to be $c$$\alpha$ , but I wanna ask that doesn't $\ce{...
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Is it possible to make strong acids using (relatively) weak acids? [closed]

One of the routes of making hydrogen chloride involves heating a mixture of sodium bisulfate and sodium chloride. Considering that the equilibrium is constantly forced to shift to the right by ...
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What is the ∆H_vap when temperature of a given liquid is equal to the boiling point of the liquid?

What is the $∆H_{vap}$ when temperature of a given liquid is equal to the boiling point of the liquid? For the other cases ie (i) T>BP, $∆H_{vap}$ > 0 (ii) T<BP, $∆H_{vap}$ < 0 So what ...
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1answer
68 views

How does the rate equation account for solids and liquids?

The question is long because I wanted to include the whole thought process. Given the hypothetical reaction: $$\ce{ A(s) + B(aq) <=> C(aq) + D(aq)}$$ One would obtain the equilibrium constant: $$...
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Which reaction is happening in the preparation of sulfuric acid through contact process?

I've read that in the preparation of $\ce{H2SO4}$ through the Contact process, on the absortion tower, the gas $\ce{SO3}$ is getting in contact with $\ce{H2SO4} (l)$ , because adding $\ce{SO3}$ to $\...
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43 views

What actually happens to the equilibrium of solid and aqueous ions in a solution when concentrations are changed?

Taking as an example the equilibrium set up when $\ce{BaSO4}$ is added to water: $$\ce{ BaSO4(s) <=> Ba^{2+}(aq) + SO^{2-}_4(aq) }$$ The solubility product constant is $[\ce{Ba^{2+}}][\ce{SO^{2-}...
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1answer
78 views

Should we consider reactant as the product of a no reaction?

If a reaction doesn't take place, should we call the reactant as the product? What is the convention? Let me illustrate the question with an example from JEE Advanced 2021, paper 1: The reaction of Q ...
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44 views

Chemical equilibria - Lab practical [closed]

In an experiment to determine the partition coefficient, how would we assure that the system has reached partition equilibrium?
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Calcium reactor and pH

In a $400$ liter aquarium, whose bicarbonate level is kept constant, it is initially equal to $122\space\text{mg/L}$ and you want to raise the $\text{pH}$ from $8.3$ to $8.48$. For this, a calcium ...
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Is dehydration of cobalt(II) chloride hexahydrate dynamic equilibrium?

I know that the dehydration of cobalt(II) chloride hexahydrate is a reversible reaction, is it a dynamic equilibrium? $$ \begin{align} \ce{CoCl2·6H2O &<=> CoCl2·2H2O + 4 H2O}\tag{R1}\\ \ce{...
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1answer
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Predicting time taken to reach equilibrium

Consider the following reaction, $\ce{A <=>[k_f][k_b] B}$, $k_f$ and $k_b$ are the rate constants of forward and backward reactions respectively. Let the initial concentration of $\ce{A}$ be $a \...
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How can a catalyst be selective if it does not change the equilibrium constants?

\begin{align} \ce{CO(g) + 3H2(g) &->[Ni] CH4(g) + H2O(g)}\\ \ce{CO(g) + 2H2(g) &->[Cu/ZnO-Cr2O3] CH3OH(g) }\\ \ce{CO(g) + H2(g) &->[Cu] HCHO(g) } \end{align} As we see here, ...
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1answer
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What would happen if I increase the pressure and temperature of a gas present in a container

Assume the gas to be a real gas and the container to be made of diamond or anything stronger than that. Take the amount of gas to be 2mL and the pressure is increased with the help of strongest ...
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29 views

At equilibrium, which one of the following is always Zero? [duplicate]

At equilibrium, which one of the following is always zero? (A)∆H (B)∆S(Total) (C)∆S(System) (D)∆G° I know that at equilibrium ∆G=0, and was facing difficulty in connecting the above mentioned ...
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Do decomposition potentials change during electrolysis?

I was just wondering if decomposition potentials actually change during electrolysis. For example, if we reversed the Daniell cell reaction so that copper is oxidized, the half cell reactions would be:...
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1answer
79 views

Calculating Gibbs free energy change when the state of ions is unknown

Problem Calculate $\Delta G^\circ$ for the following reaction: $$\ce{Zn(s) + Ag2O(s) + H2O(l) -> Zn^{+2}(aq) + 2Ag(s) + 2OH-(aq)}$$ Given $E^\circ_{\ce{Ag+/Ag}} = \pu{0.80 V}$, $E^\circ_{\ce{Zn^{+...
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Deriving kinetic equations for reversible reactions

Problem Given the reaction $\ce{A <=>[$k_\mathrm f$][$k_\mathrm b$] B}$ with rate constants $k_\mathrm f = \pu{4E-2 s-1}$ and $k_\mathrm b = \pu{10^{-2} s-1}$. Initially, $\pu{2 mol}$ of $\ce{A}...
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How much Na2O (from NaOH) do I add to sodium silicate with a weight ratio of SiO2/Na2O = 2.34 to get the solution to a weight ratio SiO2/Na2O = 1.9?

There is some confusion in industry as sodium silicate is made with NaOH but given a ratio with respect to Na2O (i.e. SiO2/Na2O not SiO2/NaOH). I presume it follows from this equation: 2NaOH -> ...
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27 views

Acid dissociation constant calculated from the ionization percentage

The question goes like this: An acid (HX) is 25% dissociated in water. If the equilibrium concentration of HX is $\pu{0.30 M}$, calculate the value of $K_\mathrm{a}$. So I tried as follows: if I ...
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Why does the reaction between copper(II) ion and iodide ion proceed even though the E_cell of the set up is negative?

(iii) Another example of a reaction that does not agree with the theoretical prediction is the reaction between $\mathrm{Cu}^{2+}$ and $\mathrm{I}^{-}$ according to the equation below. $$ 2 \mathrm{Cu}...
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103 views

What does the change in Gibbs Free Energy refer to?

Usually change is indicated as the difference between some initial and final state. However, for ΔG there seem to be multiple definitions and I am a bit confused. For example, at equilibrium, ΔG = 0 ...
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Query Regarding Activity of Pure Water [duplicate]

While calculating $K_i$ i.e. ionization constant of water, why do we put $[H_2O]=55.5M$ in the expression below:- $K_i= \dfrac{\ce{[H^+][OH^-]}}{\ce{[H_2O]}}$ $$\ce{H_2O <=> H^+ + OH-}$$ ...
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Why is it that when dG°<0, dH°<0? [closed]

Let me preface this question by saying that I probably made a mistake somewhere. However, I can't figure out what it is. I was messing around with the Gibbs free energy equation to determine how the ...
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Density and partial pressure [closed]

A sample of $\ce{NOBr}$ gas was placed in a rigid flask where it decomposes at $\pu{25 ^\circ C}$ according to the following reaction: $$\ce{2NOBr(g) <=> 2NO(g) + Br2(g)}$$ At equilibrium, the ...
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1answer
85 views

Relation between standard silver-silver chloride electrode potential and solubility product of silver chloride

I learned that $E^\circ_\ce{Cl^-|Ag,AgCl}, E^\circ_\ce{Ag^+|Ag}$ and $K_\mathrm{sp}$ of $\ce{AgCl}$ are related as $$\boxed{E^\circ_\ce{Cl^-|Ag,AgCl} = E^\circ_\ce{Ag^+|Ag} + \frac{RT}{F}\ln K_\mathrm{...
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How is the equilibrium constant for the water-gas shift reaction calculated after it is disturbed?

Consider the following equilibrium process at $\pu{686 ^\circ C}$: $$\ce{CO2(g) + H2(g) <=> CO(g) + H2O(g)}$$ The equilibrium concentrations of the reacting species are $[\ce{CO}] = \pu{0.050 M}$...
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What's the equilibrium pressure of CO2 gas over sodium hydroxide?

Many (too many) decades ago in physical chemistry lessons, I seem to recall that given the enthalpy changes of reactions, and maybe phase diagrams, one could work out what equilibrium a reaction would ...
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1answer
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Finding solubility of salts of polyprotic acids

Problem Given, for $\ce{H3PO4}$, $\mathrm{pK_\mathrm{a_1}=2.2}$ $\mathrm{pK_\mathrm{a_2}=7.2}$ $\mathrm{pK_\mathrm{a_3}=12.4}$ For the salt $\ce{Mg(NH4)PO4}$, $\mathrm{pK_\mathrm{sp}=12.6}$ and the ...
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1answer
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Intuition for relation between electrode potential and reaction quotient

Consider the following reaction in a galvanic cell: $$\ce{X(s) + Y+(aq) -> Y(s) + X+(aq)}$$ According to the Nernst equation, $$E =E_\circ - \dfrac{RT}{F}\ln\left(\dfrac{\ce{[X+]}} {\ce{[Y+] }} \...
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Sodium hydroxide reaction with manganese dioxide [duplicate]

I came across a website that said it is possible for sodium hydroxide to react with manganese dioxide at temperatures near 0 degrees Celsius. The reaction goes: 2MnO2 + 3NaOH ⇄ MnO(OH) + Na3MnO4 + H2O ...
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1answer
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Why is "activity" of gaseous component equal to its partial pressure but that of aqueous component its concentration?

While solving an electrochemistry problem I had to calculate the reaction quotient of this reaction: $$\ce{2Fe(s) + 4H+(aq) + O2(g) -> 2Fe^{2+} (aq) + 2H2O (l)}$$ It turns out to be: $$\ce{Q=\dfrac{...
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1answer
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How is the equilibrium expression (law of mass action) related to the rate law? [duplicate]

Every chemistry textbook I've read will have a chapter on the rate law. It will say something like, given a reaction $a\text{A} + b\text{B} \rightarrow c\text{C} + d\text{D}$, the rate law (for the ...
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Why aren't electrons included in the equilibrium constant expression?

This might be elementary, but why aren't electrons included in the equilibrium constant for a half-reaction? For example, for $$\ce{O2 (g) + 4H+ (aq) + 4e- -> 2H2O(l)}$$ we have $$Q = \frac{(a_\ce{...
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Why is the concentration of gases denoted in form of partial pressure? [duplicate]

In most of the chemical laws of chemistry involving concentration of products or reactants like equilibrium constant, reaction quotient, Henry's law, Nernst equation etc, I often see a similar note ...
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1answer
130 views

Numerically solving chemical equilibrium equations

Here are chemical equilibrium equations: $\begin{cases} \mathbf{N}^\text{T}\mathbf{X}+\mathbf{C}=\mathbf{Y}\\ \mathbf{N}\ln\mathbf{Y}=\ln\mathbf{K} \end{cases}$ Here $\mathbf{C}=\begin{pmatrix}c_1\\...
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1answer
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Query related to ionic equilibrium constant [duplicate]

I know that [H+][OH-] = kw =10^-14 at 25 degree.But while calculating the pH of 10^-8 M HCl, this equation is used for total concentration of [H+] and [OH-] in the solution. Why is this equation valid ...
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1answer
87 views

Can we have an equilibrium constant for a reaction at constant volume?

Suppose we have a sealed container (fixed volume) and we introduce two gases $\ce{A}$ and $\ce{B}$. The two reactants $$\ce{A + B <=> C}$$ form another gas $\ce{C}$ with equilibrium constant $K$....
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2answers
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How does the value of the equilibrium constant give information about the extent of reaction at equilibrium?

Pretty much everywhere I've read, the numerical value of the equilibrium constant gives you information about the relative concentrations of products and reactants in the equilibrium mixture; the ...
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2answers
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Phase equilibrium & phase diagram [closed]

Q) Why does phase equilibrium/inter-conversion ONLY occur at boundary lines between phases in phase diagrams? Example: According to water phase diagram, at 200 C and 200 atm ONLY liquid water ...
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1answer
55 views

Finding the molar ratio at equilibrium

Consider the reaction $\ce{SO_2_{(g)} + \frac{1}{2} O_2_{(g)}\longrightarrow SO_3_{(g)}}$. What effect is there on the molar ratio $\frac{n_{SO_3}}{n_{SO_2}}$ at equilibrium if the pressure is ...
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58 views

Doubt while using Le Chatelier's principle [closed]

Consider the following reaction $\ce{H2}+\ce{I2}\rightleftharpoons\ce{2HI}$, for this reaction $\Delta H_r<0$ Now suppose I introduce more amount of $\ce{H2}$ in it, therefore temperature of system ...
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1answer
276 views

Formation of Aniline from Chlorobenzene

My textbook says: When chlorobenzene is treated with aqueous ammonia at 473K under a pressure of 60 atmospheres in presence of cuprous oxide or cuprous chloride, aniline is formed. Notice the ...
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32 views

Equilibrium and endergonic reaction

If a reaction A <-> B has a value of dG°>0, then I know that A -> B is endergonic while A <- B is exergonic. Now if I start with 100% B I could see how equilibrium is reached, B reacts ...
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1answer
93 views

Strongest acid that can exist in water

Fundamentals of Biochemistry: Student Companion: Life at the Molecular Level[1] states that, The strongest acid that can stably exist in aqueous solutions is $\ce{H3O+}$. This is restated in the ...

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