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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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11 views

calculations buffer solution using pka and henderson's equations [on hold]

What is the $\mathrm{pH}$ of mixture of $\pu{5ml}$ of $\pu{0.1M}$ of $\ce{CH3COONa}$ and $\pu{4 ml}$ of $\pu{0.1M}\ce{ CH3COOH}$.If the $\mathrm{p}K_\mathrm{a}$ is 4.76? How is the $\mathrm{pH}$ ...
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2k views

Application of LeChatelier's principle for reactions with solid products

I wanted to understand application of LeChatelier's principle for reversible reactions of type $\ce{A(g) <=> B(g) + C(s)}$. Because of increase in moles, you can say lower pressure will favor ...
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17 views

Ka for reaction from tables [duplicate]

For the reaction below: NH4+ + H2O -> NH3 + H30+ I have the following values from a table to use: And in the solution manual they tell me to use the Ka for this reaction. Why is this? Why do we ...
8
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676 views

What is the difference between chemical equilibrium and dynamic equilibrium?

Is chemical equilibrium and dynamic equilibrium the same thing? Both point to the reversible reactions and no net changes in the concentrations of product and reactant. Dynamic equilibrium from ...
6
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2answers
3k views

Why is ortho-hydroxybenzoic acid more acidic than its para-isomer?

Why is ortho-hydroxybenzoic acid $(\mathrm{p}K_\mathrm{a} = 2.98)$ more acidic than its para-isomer $(\mathrm{p}K_\mathrm{a} = 4.58)$? March's Advanced Organic Chemistry (7th ed) gives the reason to ...
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Original reference of multiplicative coupled equilibria [closed]

Can I know what is the peer-reviewed reference behind the multiplicative nature of two equilibrium constants of two reactions that are additive? Example:
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2answers
9k views

Calculating equilibrium constants: adding two or more equations

If two or more reactions are added to give another, the equilibrium constant for the reaction is the product of the equilibrium constants of the equations added. How is this true? What is the reason?...
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How to calculate the composition of a borate buffer with a defined pH using the Henderson-Hasselbalch equation?

I am struggling with what appears to be an extremely easy pH problem that uses the Henderson-Hasselbalch equation. The problem and answer provided by the book is given below. I understand where the ...
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31 views

Thermochemical data for thiocyanatoiron(III) ion

I am currently writing a lab report about the formation constant of $\ce{FeSCN^2+}.$ All I could find online was a formation constant at $\pu{25 °C}$ $(890),$ which was 70% higher than the ...
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23 views

Find the concentration of each substance at equilibrium

I have a question that asks me to find the concentration of each substance when the equilibrium of the reaction is established: We pour $\pu{0.02L}$ of $\ce{Ba(NO3)2}$ ($\pu{0.1 mol/L}$) into $\pu{...
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1answer
18 views

Chemical equilibrium [duplicate]

When calculating equilibrium constant with partial pressures if there is a solid involved should we consider it in the total number of moles in mole fraction?
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1answer
52 views

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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4k views

How does equilibrium change when pressure is increased? [closed]

What happens to the equilibrium when an increase in pressure is applied to a system with the same number of moles of gas on both sides of the reaction, according to Le Chatelier's Principle? For ...
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1answer
34 views

Equilibrium expression for dissolution of carbon dioxide

I was asked to give the equilibrium expression for: $$\ce{CO2(aq) + H2O(l) <=> H2CO3(aq)}$$ As water is a liquid and a solvent here, it shouldn't be included in the expression, hence I wrote: ...
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1answer
20 views

What exactly causes equilibrium to shift when pressure is decreased? [duplicate]

Take the reaction: $$\ce{N2(g) + 3 H2(g) <=> 2 NH3(g)}$$ If pressure is decreased, equilibrium shifts to the left because it has more moles. I understand the basics of why this is, i.e. due to ...
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Using Le Chatelier's Principle to Change Mechanical Energy to Chemical Energy

I was interested in an application of Le Chatelier's principle, where an increase in pressure could result in a decrease in the moles of gas. In particular, a situation where when the pressure ...
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3answers
159 views

melting and boiling …really equilibrium? [closed]

Why are melting and boiling considered equilibrium processes even though the amount (concentration) of both phases keep changing i.e from solid to liquid and so on?
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1answer
57 views

How is a phase equilibrium defined for a one-component system?

A question on this site asked whether a one-component system is at equilibrium when melting or boiling, and the disparate answers were somewhat dependent on the definition of phase equilibrium. ...
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2answers
38 views

Equilibrium of an electrochemical cell [closed]

I am quite new to the field. So try to figure out what is meant by the equilibrium state of an electrochemical cell? Is it, where both half cells passing the same number of electrons to either side? ...
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2answers
535 views

Effects of pressure on equilibrium

Which system at equilibrium will not be influenced by a change in pressure? (A) $\ce{3O2(g)<=> 2O_3(g)}$ (B) $\ce{N2(g) + 3H_2(g)<=> 2NH_3(g)}$ (C) $\ce{2NO_2(g)<=> ...
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1answer
42 views

Gibbs energy derivative vs equilibrium for aqueous reaction

I am trying to find the Gibbs-energy equilibrium for the reaction $$\mathrm{A}+\mathrm{B}\rightleftharpoons\mathrm{C}.$$ According to most sources the equilibrium concentrations in an ideal solution ...
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How are σ+ values in Hammett Plots calculated?

First of all, I know a similar question has already been asked & answered about σ values in general, however, I am not 100 % sure this answer is correct for the following situation. So for the σ ...
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2answers
3k views

Finding the kp with density, temperature, and pressure

Consider the following reaction $$\ce{3O2(g) <=> 2O3(g)}$$ At $\pu{175°C}$ and a pressure of $\pu{128Torr}$, and equilibrium mixture of $\ce{O2}$ and $\ce{O3}$ has a density of $\pu{0....
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Azeotropic Distillation - Am I interpreting this VLE diagram correctly?

I've been looking at ways to re-concentrate a formic acid-water binary mixture with the VLE diagram below. Am I correct in saying that to concentrate a solution of say , 40% formic acid by weight I ...
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Does putting a reversible reaction out of equilibrium affect temperature?

Lets say we have a reversible reaction in equilibrium A + B <--> C. It's exothermic towards the right. Would increasing the concentration of A or B cause a temporary increase in temperature from ...
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1answer
79 views

Cases when Raoult's law is unsolvable

Setup Consider a closed binary mixture of known total molar composition $n_i$, held at volume $V$ and temperature $T$. The equilibrium phase composition is determined by $\mu_i^{vap} = \mu_i^{liq}$. ...
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1answer
96 views

Spectroscopic Determination of an Equilibrium Constant [closed]

I got values of $\pu{5.0E-4}$, $\pu{2.5E-4}$, and $183$ for the following problems. However, these seem to be inaccurate and I'm not sure what to do. Here is the procedure: Obtain 6 disposable ...
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59 views

Gibbs free energy of phosphorus pentachloride decomposition reaction

The equilibrium constant at $\pu{227 °C}$ for the equation $$\ce{PCl5(g) <=> PCl3(g) + Cl2(g)}$$ is $K_p = \pu{4.50E3 bar}.$ Calculate the value of $Δ_\mathrm{rxn}G^\circ$ at $\pu{227 ...
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2answers
126 views

Calculating partial pressure of carbon monoxide

$\ce{ZnO}$ is exposed to pure $\ce{CO}$ at $\pu{1300 K}$ and the equilibrium $$\ce{ZnO(s) + CO(g) <=> Zn(g) + CO2(g)}$$ is then established at $\pu{1 atm}$ pressure. The density of the ...
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1answer
27k views

Why is Kc not affected by change in pressure?

Why is $K_c$ not affected by change in pressure? I know the mathematical explanation, but I don't really understand the reason when only looking at $K_c$. The explanation I know is with the reference ...
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2answers
63 views

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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1answer
171 views

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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1answer
147 views

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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1answer
143 views

Is a discharged battery in a state of chemical equilibrium?

A reaction that has reached chemical equilibrium no longer shows changes in reactant and product concentrations, but forward and reverse reactions are still going on. I'm confused whether a completely ...
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2answers
48 views

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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1answer
45 views

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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2answers
59 views

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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1answer
36 views

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/...
5
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2answers
207 views

Clausius–Clapeyron relation for states of water and vapor

I've seen many questions about this topic on this site, but I still have some issues trying to understand this aspect. Here's what I believe I understood looking at the phase diagram for a pure ...
4
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2answers
124 views

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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3answers
95 views

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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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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1answer
100 views

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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2answers
258 views

Find the pH of an amphiprotic salt dissolved in water at room temperature

Let's say I have a polyprotic acid $\ce{H2A}$ with the following properties: $$ \begin{align} \ce{H2A &<=> HA- + H+} & K_1 &= 1\cdot 10^{-1}\\ \ce{HA- &<=> A^2-+ H+} & ...
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3answers
2k views

Prove that a Change of Volume will not Change the Value of the Equilibrium Constant

According to my book, a decrease in volume will result in an increase in pressure for an equilibrium mixture, which will in turn cause its equilibrium to shift to the side with the least number of gas ...
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0answers
15 views

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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How to determine the pH of a mixture of two weak acids?

We’ve two solutions: Solution 1 $\ce{HCOOH}$ its concentration is $c_1=10^{-2}\ \mathrm{mol/l}$ and its volume is $V_1 = 50\ \mathrm{ml}$ and its $\mathrm{pH}_1 = 2.9$. Solution 2 $\ce{CH_3COOH}$ ...
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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 ...
6
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1answer
201 views

Apparent contradiction in the type of deviation of an ethanol-water mixture

For a mixture of $\ce{EtOH}$ and $\ce{H2O}$: $\Delta H_{\text{mix}} < 0$ (exothermic) and $\Delta V_{\text{mix}} < 0$ (volume contraction). This means that the unlike interactions are stronger ...
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39 views

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?