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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Finding Equilibrium Constant

Consider the following equilibrium process at 686˚C: CO2(g) + H2(g) <=> CO(g) + H2O(g) The equilibrium concentrations of the reacting species are [CO] = 0.050 M, [H2] = 0.045 M, [CO2] = 0.086 M, ...
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What happens to the equilibrium constant Kc when adding a strong electrolyte to the reaction? [closed]

If given a chemical reaction in a water based solution with a certain equilibrium constant $K_c$ , and a strong electrolyte is added to the solution, how would it effect $K_c$?
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How come G=Go+RTlnK when, G = H-TS?

So, somebody said, "The gist of the derivation relies on an understanding of the patition function, and how this function relates the quantum mechanical properties of the molecules to the ...
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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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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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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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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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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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Is chlorine gas evolve from the reaction between manganese dioxide sodium hydroxide and bleach? [closed]

Apparently the overall reaction would be $$\ce{2 MnO2 + 3 NaClO + 2 NaOH -> 2 NaMnO4 + 3 NaCl + H2O}.$$
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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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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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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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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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Le chateliers principle and pressure [duplicate]

Why does a decrease in pressure shift the equilibrium towards more numbers of moles and increase in pressure shift the equilibrium towards less number of moles?
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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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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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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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Effect of temperature on position of equilibrium through Le Chatelier's principle

When the temperature of the equilibrium mixture is increased, the position of the equilibrium shifts towards the endothermic side. I am aware of the actual cause of this (equilibrium constant changing)...
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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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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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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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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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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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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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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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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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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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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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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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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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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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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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Regarding Ellingham diagrams

In my textbook, the following information is given about Ellingham diagram: The interpretation of $\ce{\Delta_rG^\circ}$ is based on ${K}$ ($\ce{\Delta G^\circ = -RTlnK}$). Thus it is presumed that ...
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Can physical absorption happen despite the formation of products?

As far as I know, the absorption of $\text{SO}_2$ in water goes under physical absorption, meaning the sulfur dioxide bubbles are held in place by Van der Waals forces, in this case Keesom forces, ...
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Why does the dissolution of calcium hydroxide have a negative entropy?

We had an experiment on the dissolution of calcium hydroxide and we obtained the experimental entropy value $\pu{-203 J mol^-1 K^-1}$ with a percent error of $26.7\%.$ Doesn't dissolving a solid in a ...
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Apparent paradox in the formation of ice at room temperature

The formation of ice out of liquid water can be written down like this: $$\ce{H2O (l) <=> H2O(s)}$$ We can calculate the change in standard Gibbs free energy (per mol substance) in the following ...
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pH for an HA/NaA solution using a contour map

The following question has troubled me for a while now. A virtual weak acid $\ce{HA}$ dissociates as follows: $\ce{HA <=> H^+ + A^-}$ with the acid dissociation constant $K_\mathrm{a} = 10^{-3....
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Relative humidity and vapor-pressure in equilibrium

I have quite an unclear understanding of relative humidity. I am writing my understanding on the topic and please correct me wherever I'm wrong: What I understood: Let's say $\ce{H2O}$ has a (...
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Preparation of phosphate buffer of ph 7.4

Can I make a phosphate buffer of pH 7.4 starting with phosphoric acid and then adding NaOH until the pH reaches 7.4. What are the disadvantages of using this method over sodium phosphates?
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Ambiguity in the direction of dissolution equilibrium

The following reaction is usually carried out to test for the carbonate anion in an inorganic salt; $$\ce{CO3^2- +BaCl2/CaCl2 -> BaCO3/CaCO3(s) + 2 Cl-}$$ The resulting carbonate is stated to be an ...
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Standard Gibb's Free energy change, standard state and equilibrium

I just want to confirm if I am right in thinking that: statement: When a reaction in standard state is in equilibrium, then equilibrium constant K=1 Reason: since in a equilibrium, $Q=K$ and $ΔG=0$. ...
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Osmotic Pressure of Aqueous Solution

The osmotic pressure of an aqueous solution at $25$ Celsius is $92.0$ $kPa$. Calculate the boiling point of the solution. (Assume that the density of the solution is $1.0$ $g/mL$, ignore the mass of ...
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Enthalpy in the van't Hoff equation

In the van't Hoff equation, why do we say that the change in enthalpy at standard pressure is constant? My book derives the equation for a mixture of ideal gases reacting with each other. The proof ...
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Complex formation in water and Henry's law

I've been trying to solve the following problem for a while now. Consider a mixture of two different gases ($A$ and $B$) for which Henry's law holds. When gas molecules $A$ and $B$ do not interact ...

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