# 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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### Calculating Kp in two different ways

The degree of dissociation of $\ce{NH3}$ at $\pu{1 atm}$ is 20 % as follows: $$\ce{2NH3 <=> N2 + 3H2}$$ I follow two ways but end up with two different answers. Here, I assume that ...
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### Find the half equivalence point

How to find the half equivalence point knowing the pH, molarity, titrant added at equivalence point? This a fairly straightforward and simple question, however I have found many different answers to ...
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### Ionic Product of Water

Why is the ionic product for water ($K_\text{w}$) temperature dependent? The concentration of $\ce{H+}$ and $\ce{OH-}$ ions in pure water is $[\ce{H+}] = [\ce{OH-}] = 1.0\times 10^{-7}\ \mathrm{mol/l}$...
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### What is the value of dissociation constant of water at 25°C [duplicate]

According to my class notes, $$K_{dissociation} = \frac {[H^+][OH^-]}{[H_2 O]}$$ $$= \frac {10^{-14} }{55.55}$$ $$= 1.8 * 10^{-16}$$ But shouldn't we ignore concentration of water (55.55 M) as ...
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### How identify acid and base for Henderson-Hasselbach equation [closed]

If I am asked to determine the pH in e.g. 60 mM Na2CO3 and 30 mM NaHCO3 or 50 mM NaHSO4 and 40 mM Na2SO4 How do I go about to identify which of these two is the base and which is the acid? ...
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### Finding the molarity of an unknown weak acid when its pH and volume is given

In lab we measured the pH of $\pu{25.0 mL}$ of an unknown acid. The pH was $2.43$. I’m supposed to figure out the molarity. How? I don’t know the $K_a$ or anything. Volume seems useless. I really just ...
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### equilibrium reactions [closed]

How will the equilibrium of following reactions be affected 1) N2(g) + O2 (g) ⇄ 2NO(g); 2) 4HCl(g) + O2(g) ⇄ 2Cl2(g) + 2H2O(g) a) by rise of pressure; b) by decrease of oxygen concentration? Explain ...
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### Derivation of relationship between equilibrium constant and Gibbs free energy change

Why is $\Delta G=\Delta G^o+RT\ln Q?$ It feels like all online sources were written for introductory Chemistry students! Where do I find a rigorous proof of this identity? Greatly appreciate it!
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### Why does equilibrium exist?

I've read an article that equilibrium exists when $G$ (Gibbs free energy) becomes minimum. If formation of products decreases Gibbs free energy, why won't the reaction proceed to completion so that ...
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### Why is water ignored in the ionic equilibrium of HF?

While trying to understand the solution of a problem given in my textbook, I realized I'm having some difficulty with the solution. The problem is as follows: The ionization constant of $\ce{HF}$ ...
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### Description of a van't Hoff apparatus

A "van't Hoff apparatus" is mentioned as a means of performing a reaction involving gases in a reversible manner, for instance here. Unfortunately I have been unable to find a description of such a ...
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### How to explain that an increase in temperature favours an endothermic reaction?

I'm trying to explain how a change in temperature favours an endothermic/exothermic reaction from a collision theory point of view, but I'm not really familiar with the concept just yet. For an ...
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### Question about change in pressure and change in temperature for system at equilibrium

I was reading my Chemistry textbook and I noticed that it stated that for a system at equilibrium: At constant temperature, reducing the volume of gaseous equilibrium mixture causes the system to ...
99 views

### Will NaF + CaCO3 precipitate much CaF2?

If I mix sodium fluoride, calcium carbonate powder, and water, under what conditions (if any) would there be an equilibrium? I.e. assume we start out with fully dissociated $\ce{Na+(aq) + F-(aq)}$, ...
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### Is there a name, or any specific jargon for a precipitation equilibrium involving a solid reactant?

Let's say you have some ions in solution, for example Na+(aq) and OH-(aq), and some partially dissolved solid, MgCO3(s), Mg+2(aq) and CO3-2(aq), which precipitates Mg(OH)2(s) until equilibrium. So ...
257 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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### How to manage complex equilibria when studying a mecanism?

Consider a complex multistep reaction mechanism with several intermediates. There are multiple possible pathways as well as equilibria in solution. One wants to study the reaction mechanism using ...
Imagine an initial 50%-50% mixture of normal ($\rm H_2 \rm O$) and heavy water ($\rm D_2 \rm O$). I think, simply mixing them, the result will exponentially converge to an equilibric state, where ...