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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2answers
55 views

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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Does addition of reversible and irreversible reaction gives a reversible reaction or irreversible reaction? [closed]

There are 2-3 questions related to it . Does every reaction has a equilibrium constant ? (even the irreversible one's ?) I have read that any acid having pKa < -1.7 dissociates in water ...
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1answer
30 views

Why does the side with more moles of species always get affected the most in pressure/volume, and dilution changes?

I understand how LCP works in favouring the side with more moles of gas, if the imposed change is a decrease in pressure. Or vice versa, if the imposed change is an increase in pressure the side with ...
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1answer
25 views

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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35 views

Is phase change an equilibrium process

I understand that if we keep water at $100^{\circ}$C, it will have no tendency to form vapor( that is $\Delta G=0$) until heat is added to it, and that added heat increases the potential energy of ...
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26 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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32 views

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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1answer
24 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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2answers
99 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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39 views

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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50 views

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
83 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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1answer
64 views

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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42 views

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
65 views

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
33 views

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
29 views

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
23 views

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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63 views

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
117 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
81 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
63 views

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
74 views

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
53 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
247 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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31 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
90 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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1answer
98 views

Calculating pH of aqueous ammonium hydrogen sulfide solution

I was doing the following question yesterday: Calculate the pH of a $\pu{0.1 M}$ solution of $\ce{NH4HS}$, given $\mathrm{p}K_\mathrm{b}$ of $\ce{NH3}$ is $4.74$, and $\mathrm{p}K_\mathrm{a1}$ and $\...
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While adding simultaneous equilibria , when is the dissociation constant of both reactions the same?

I have a doubt regarding chemical and ionic equilibrium .In reactions involving simultaneous equilibria , instead of analysing the equilibrium simultaneously we sometimes add/substract both the ...
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1answer
68 views

Cause of reversible reactions in terms of Gibbs free energy

Heading I recently learned about the standard Gibbs free energy change of reaction, ΔG=ΔH-TΔS, and how its sign indicates whether the conversion of (ALL) reactants and products is spontaneous or not. ...
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1answer
204 views

What does the state of a substance at a specific T and P mean?

From the phase diagram of water, we see that water is a liquid at 20°C, 1 atm. The state of the water at 20°C, 1 atm is liquid. But there is actually also a water vapor in equilibrium with liquid ...
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How can the activity of ions be more than 1 if the activity of water is 1?

Now, I am quoting Chemlibretexts when they give the activity coefficient of $\ce{LiCl}$ to be $\pu{1.026}$ at the molality of $\pu{2.5 mol kg-1}$ For simplicity, assuming this is aqueous, I'll just ...
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1answer
85 views

How to calculate Kp without knowing the volume? [closed]

I have the following chemical equation: $$\ce{Sb2S3 + 3H2 <=> 2 Sb + 3H2S}$$ I have $\pu{1000 grams}$ of $\ce{Sb2S3}$ that reacts with $\pu{10 grams}$ of $\ce{H2}$ in a reactor at $\pu{713 K}$. ...
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26 views

In an equilibrium with solvent in reaction, when we want to determine the reaction direction, do we account for the 55.6 mol/L of water? [duplicate]

Usually when we calculate the equilibrium of a reaction with a solvent, the solvent is ignored whether it is a reactant or a product. For example when $$\ce{CH3COOH +C2H5OH <=> CH3COOC2H5 +H2O}$$...
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1answer
53 views

How are acids in aqueous solution able to react again after reacting with water?

I hope to clear up some confusion I have about acid-base reactions in aqueous solution. Based on the Bronsted-Lowry definition of acids, I know acids donate protons. In water, a strong acid should ...
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1answer
31 views

Is equilibrium point for a coupled equilibria of arbitary number of coupled reactions is a unique point?

I was solving a question of salt hydrolysis for a mixture of Weak Acid-Base Salts, given the initial amount of salt and Equilibrium constants. I was trying to approach the problem in two ways, ...
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Do the differential expressions of second law of thermodynamics imply a smooth increase in entropy? [closed]

Another statement of second law of thermodynamics can be formulated in terms of system properties and not properties + surroundings (isolated system). For a closed system at constant temperature and ...
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1answer
72 views

Effect of addition of inert gas on concentration in an equilibrium [duplicate]

We have the following equilibrium established in a container with movable piston at atmospheric pressure. $$\ce{N_2 (g) + 3 H2 (g) ⇌ 2NH_3 (g)}$$ Now how does the concentration of the reacting species ...
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3answers
214 views

Why is standard state useful?

In order to calculate the equilibrium constant we must know the value of $\Delta_\mathrm{r}G^{\circ}$ (which is a function of $T$) so we can calculate $K$ as: $$K = \exp\left(-\frac{\Delta_\mathrm{r}G^...
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Is tetrachloridocuprate(II) formed when dilute hydrochloric acid is added to a solution containing tetraamminecopper(II)?

As observed in the lab, when concentrated $\ce{HCl}$ is added to a solution of deep blue $\ce{[Cu(NH3)4]^2+}$ a green color appears indicating the partial formation of the yellow colored $\ce{[CuCl4]^...
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1answer
727 views

Can the equilbrium constant ever be exactly 1?

According to my book, In the real world [...] it is unlikely that any reaction would have exactly equal concentrations of products and reactants at equilibrium. This was mentioned in context to the ...

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