Questions tagged [equilibrium]

The state in which both reactants and products are present at concentrations which have no further tendency to change with time.

Filter by
Sorted by
Tagged with
-1
votes
1answer
29 views

Finding the error in attempting the equilibrium question through isotherm equations

Consider the partial decomposition of A as: $$\ce{2A(g) <=> 2B(g) + C(g)}$$ At equilibrium $\pu{700 ml}$ of gaseous mixture contains $\pu{100 ml}$ of gas C at $\pu{10 atm}$ and $\pu{...
1
vote
1answer
105 views

Why is the equilibrium constant unaffected by a change of the initial concentration?

In my class, it was taught that the equilibrium constant does not vary with the intial concentration of the reactants? Why is it so?
1
vote
2answers
94 views

Why is the concentration of protons equal to the concentration of a strong acid?

First, I know that strong acids are assumed to dissociate completely in water, so that the concentration of $\ce{H+}$ which they provide equals their concentration. What I am asking for is not the ...
1
vote
1answer
64 views

Buffer made of salts of polyprotic acid: reactions

I was trying to make a buffer with $\ce{K2HPO4}$ to use it in a bacterial culture. If I use $\ce{K2HPO4}$ I think I have to add $\ce{KH2PO4}$. I am trying to think it writing the equations of the ...
-2
votes
4answers
2k views

Titration of Na2CO3 against HCl

$\pu{25 mL}$ of $\pu{0.125 M}$ $\ce{Na2CO3}$ is titrated with $\pu{0.100 M}$ $\ce{HCl}$. Given that $K_\mathrm{a1} = 4.3\times 10^{-7}$ and $K_\mathrm{a2} = 4.8\times10^{-11}$ for the diprotic acid $\...
1
vote
0answers
337 views

Difference between Henry constant and equilibrium constant

According to wikipedia, Henry constants define the ratio between the aqueous and gas fraction of a chemical species at equilibrium. Lets consider Henry constants H in atm.L.mol-1 such that $[C]_{g} = ...
2
votes
0answers
166 views

How to without calculations understand the liquid-liquid extraction efficiency?

I'm asking myself this question for a very long time and I haven't found a simple an good explanation yet for the fact that it's better (if you want to clean them) to wash your hands two times with ...
-1
votes
1answer
45 views

Rate of a reaction [duplicate]

We know that the rate of a reaction $\ce{aA + bB -> cC + dD}$, the rate of the forward reaction is given by $r_\mathrm f = k_\mathrm f[\ce A]^p[\ce B]^q$ where $ a\neq p$ and $ b\neq q$ according ...
-1
votes
1answer
172 views

Why don't buffer solutions return to equilibrium?

Suppose I want to make a buffer solution in any of the three ways possible with dihydrogen phosphate as my weak acid. In the first way, a certain ratio of the weak acid and its conjugate base are ...
4
votes
3answers
87 views

Equilibrium for very small amounts of reactants

Is there any difference in the concept of equilibrium when it comes down to dealing with extremely small amounts of reactants? Say we have $$\ce{A + B <=> C + D}$$ and $K_c$ is $100,000$. If ...
1
vote
2answers
105 views

How does the equilibrium shift when concentration of reactant and product are increased simulatenously

Before answering my question, take a look at this example $$\ce{2NOCl <=> 2NO + Cl2}$$ Let's suppose I have 2 mol/l $\ce{NOCl}$, 2 mol/l $\ce{NO}$, and 1 mol/l $\ce{Cl2}$ in a closed system. ...
-1
votes
1answer
65 views

How do I calculate the amount of polyprotic acid and base needed to achieve a certain buffer pH?

e.g. Citric Acid and Trisodium Citrate $\ce{H3C6H5O7 <=>[ka_1] H2C6H5O7- + H+ <=>[ka_2] HC6H5O7^2- + H+ <=>[ka_3] C6H5O7^3- + H+}$ Using the definition of Ka and substituting for ...
1
vote
0answers
44 views

Limiting factor on Belousov-Zhabotinsky reaction

In the thin film Belousov-Zhabotinsky reactions (popular on Youtube/in chemistry demonstrations), concentric rings of different colors propagate across a petri dish for minutes to hours as the ...
0
votes
0answers
61 views

Reason for formation of bubbles at boiling point [duplicate]

As I understand it, boiling takes place when the saturated vapour pressure equals to the atmospheric pressure. But, why does the vapour pressure need to be equal to the atmospheric pressure for ...
1
vote
1answer
89 views

Heat generation in exothermic reactions [duplicate]

Im thinking specifically of N2 + 3 H2 ⇌ 2 NH3. Its an exothermic reaction, therefore heat is generated. Im trying to understand how Chateliers principle interacts with this reaction. I understand that ...
-1
votes
2answers
372 views

Calculate pH of a mixture of a strong base and acid. Knowing only the pH, wt/v%, and volume of both solution. [closed]

Title explains all. I have been stuck on this for an hour and for some reason cannot understand it. I have tried to do an ICE table but get stuck halfway as I do not know whether I would use the w/v ...
1
vote
1answer
269 views

Why doesn't pH = pKa1 in the buffer zone for this titration?

Below is an image from my textbook representing the titration curve for the titration of $5.00\ \mathrm{mL}$ of $0.010\ \mathrm M$ $\ce{H2S2O3}$ with $0.010\ \mathrm M$ $\ce{KOH}$, which has $\mathrm ...
4
votes
0answers
80 views

Computing the turbulent flame length

There is a problem I found online for practice that I cannot solve: Problem Methane, $\ce{CH4}$, emerges from a $1\ \mathrm{cm}$ diameter nozzle at a rate of $120\ \mathrm{cm^3/s}$ and a mole ...
2
votes
1answer
268 views

Why are the concentrations in the equilibrium constant multiplied? [duplicate]

$$\alpha\,\mathrm{A}+\beta\,\mathrm{B}+\cdots\rightleftharpoons \rho\,\mathrm{R}+\sigma\,\mathrm{S}+\cdots$$ The equilibrium constant for this reaction can be calculated using the following formula: $...
0
votes
1answer
106 views

What does it mean for an equillibrium to move? [duplicate]

Le Chatelier's principle was described to me as: If a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium moves to counteract the change. I do not understand ...
-1
votes
1answer
33 views

Ionproduct of Water [duplicate]

The ionproduct of pure water is well known to be $$ K_{\rm W} = \left[ {\rm OH^-} \right] \left[ {\rm H_3O^+} \right] = 10^{-14} $$ at some standard conditions (I think 25°C). However having some ...
0
votes
1answer
4k views

How to calculate pH of the Na2CO3 solution given ambiguous Ka values

This is the exact question I faced on an exam. Calculate the pH of $\pu{0.05 M}\ \ce{Na2CO3}\ (\ce{H2CO3}: K_\mathrm{a,1}= 4\times 10^{-7},\ K_\mathrm{a,2}= 4.7\times 10^{-11})$ Solution $$\ce{...
1
vote
0answers
34 views

Is there a thermodynamic explanation for how a substance behaves based on its pKa and the solution’s pH?

If the pH of the solution is lower than the pKa of the compound, then the compound will be protonated, because pH is a measure of the concentration of protons, and low pH means a high proton ...
0
votes
2answers
485 views

What is the relationship between the constant of equilibrium (Kc) and the position of equilibrium? [duplicate]

I understand that the constant of equilibrium is a ratio of the concentration of the products to the reactants and that this value allows one to estimate whether the position of equilibrium lies to ...
5
votes
2answers
721 views

Calculate pH of a weak acid and weak base neutralization reaction

I'm an industrial pharmacist needing some help with some chemistry basics. I'm trying to calculate the theoretical pH of an effervescent preparation containing 2 mmol citric acid ($\ce{H3C6H5O7}$), 4 ...
-1
votes
1answer
324 views

Is it possible to calculate the Kc for an irreversible reaction? [closed]

Is it possible to calculate the Kc for an irreversible reaction? For instance, can we Calculate the $K_c$ for: $$\ce{NaCl + AgNO3 -> NaNO3 + AgCl}$$
1
vote
0answers
46 views

How does association within vapor or dissociation within liquid affect the ideal nature of a binary solution?

As I understand, when there is positive deviation of a binary solution from Raoult's Law, the equilibrium partial pressure curve approach ideality (i.e a straight line dependence of equilibrium ...
1
vote
1answer
509 views

Finding equation of line of the P-T graph for a gas dissociation reaction

Gas A (1 mol) dissociates in a closed rigid container of volume 0.16 lit as per following reaction. $$\ce{2A (g) -> 3B (g) + 2C (g)}$$ If degree of dissociation of $\ce{A}$ is 0.4 and ...
1
vote
0answers
66 views

Calculating the pH of a weak acid from the Kb of its conjugate base

I'd start off by saying it's been many years since I was in chemistry lessons and have forgotten much, but recently I have had to relearn a lot of basic chemistry. The following doesn't really impede ...
0
votes
1answer
67 views

Chemical equilibrium constant problem

In a equilibrium reaction $\ce{CO {(g)} + H2O {(g)} <=> CO2 {(g)} + H2 {(g)}}$, initial concentrations of $\ce{CO}$ and H2O are equal and are 0.3 mol/dm3. What is the equilibrium constant of ...
1
vote
0answers
48 views

What reactions will occur at the anodes and electodes of two iron electrolytic cells?

What reactions will occur at the anodes and electrodes of two iron electrolytic cells: both with iron metal electrodes, one with an iron(II) sulphate electrolyte, the other with an iron(III) sulphate ...
4
votes
1answer
353 views

Why do my equilibrium calculations on this HF/NH4OH buffer system not match those in literature?

I've been trying to reproduce Figure 2 from this research paper (full text available). The Problem However I can't seem to get the same values as in the paper. I did the math both by hand and with ...
0
votes
1answer
49 views

Measure of partial pressure on blood

Here is the issue of blood gases partial pressure. On medical reports is common to see partial pressure of gas on blood, usually oxygen, but there is no gas in equilibrium with blood, so it is ...
6
votes
2answers
349 views

Why do most carboxylic acids have high pKa (~5) in spite of having a conjugate base ion that is stabilized by resonance?

This is from my textbook: Carboxylic acids owe their acidity ($\mathrm pK_\mathrm a$ of about $5$) to the resonance-stabilized carboxylate anions formed by deprotonation. Why are they such weak ...
1
vote
1answer
959 views

How to calculate the equilibrium constant of acetic acid-hydroxide ion equilibrium?

I am trying to calculate the equilibrium constant of the following equilibrium: $$\ce{CH3COOH (aq) + OH- (aq) <=> CH3COO- (aq) + H2O (l)}$$ I am aware that this reaction essentially goes to ...
2
votes
1answer
350 views

Why is the equilibrium constant of water with its vapour equivalent to its vapour pressure?

Can someone conceptually explain why the equilibrium constant is equivalent to the vapour pressure of water for the above equilibrium reaction? For example if $K = x$, then it is said that vapour ...
1
vote
2answers
374 views

Why are temperature and pressure represented as the number 2 in Gibbs' Phase Rule?

In our class we are learning about Gibbs' Phase Rule; $F=C-P+2$, in which $F$ stands for degree of freedom, $C$ for number of components, and $P$ for number of phases in the system. Our professor told ...
-2
votes
1answer
503 views

Calculating PH of solution after adding strong acid (equilibrium)

Consider the classic example when talking about acids and bases: Say you have 1M of $\ce{HCL}$ and you throw it into water, calculate the resulting pH (= concentration of $\ce{H3O+}$). The way this ...
1
vote
2answers
219 views

Why does pH increase as a weak acid becomes more dissociated?

From Wade's Organic Chemistry [1, p. 71]: In most cases, the $\mathrm{p}K_\mathrm{a}$ of an acid corresponds to the $\mathrm{pH}$ where the acid is about half dissociated. At a lower (more acidic) ...
-3
votes
1answer
298 views

What mass of potassium lactate is needed to 300.0 mL of 0.238 M Lactic acid solution to make a solution with a pH of 4.00? pKa (lactic acid) =3.86

Upon attempt, I've yielded an answer of 11.91g. My calculations do not take 300 mL Lactic acid solution into account, and now I somewhat know the error is at least partially due to the fact that my ...
5
votes
1answer
127 views

What exactly is entropy? [closed]

I have looked at other questions, videos and articles but I kept reading disorganization, messiness or energy distribution (probability) or a thermodynamical equilibrium and stuff. What do we mean by ...
1
vote
1answer
174 views

Energy at constant Entropy and Volume

The system of constant entropy and constant volume will attain the equilibrium in a state of minimum energy. Why? I know that: $\Delta G= \Delta H-T\Delta S$ And at constant volume and entropy: $\...
1
vote
1answer
595 views

Equilibrium constant Kp for vaporization of water?

For the reaction H2O(l) -->H2O(g) it is given that Kp = p(H₂O(g))/p° where p° is the atmospheric pressure. Why is it not just equal to p(H₂O(g))?
3
votes
0answers
58 views

Reverse rate coefficient for thermolecular and thermal dissociation reactions

I am an astrophysicist working in exoplanetary atmosphere chemistry right now, in particular modelling the chemical kinetics taking place within the atmosphere. Based on this IOP article, we have that ...
1
vote
2answers
420 views

How does Le Chatelier's principle apply to a gas phase reaction at constant volume?

This reaction is given in my book and the direction of shift of reaction on addition of $\ce{CO}$ and removal of $\ce{CO2}$ at constant volume is asked. $$\ce{2CO(g) + O2(g) ⇌ 2CO2(g) + \Delta H}$$ If ...
1
vote
0answers
114 views

Different values of concentration of product at equilibrium

$\pu{60g}$ of acetic acid and $\pu{46g}$ of ethyl alcohol are mixed with each other at a constant temperature and allowed to attain equilibrium. At equilibrium $\pu{58.2g}$ of ethylacetate and $\pu{...
2
votes
2answers
805 views

Are the best buffers those that are in a 1:1 ratio with its conjugate acid/base?

I wanted to comment this, but I don't have enough reputation, so I just made this a question. I know that buffers and their conjugate base/acid must exist in similar amounts for the buffer to be ...
0
votes
2answers
4k views

How do I find the theoretical pH of a buffer solution after HCl and NaOH were added, separately?

This question is about the theoretical pH of a buffer solution. Calculate the theoretical pH values expected for a $\pu{200mL}$ buffer solution containing a 1:1 ratio of acetic acid and sodium ...
0
votes
0answers
1k views

Calculating the pH of a solution of sodium carbonate

I've seen similar questions on this site, but I'm having trouble as my book said something else. For a $\pu{0.09989 M}$ solution of $\ce{Na2CO3}$, my book said: $$\ce{Na2CO3 + 2H2O -> H2CO3 + 2Na+ ...
1
vote
1answer
90 views

Approximated formula of acid dissociation constant

$K_\mathrm{a}$ can be expressed as $K_{\mathrm{a}} = \frac{[\ce{H^{+}}] [\ce{A^-}]} {[\ce{HA}]}$, however, it can be approximated that $K_{\mathrm{a}} = \frac{[\ce{H^{+}}]^{2}} {[\ce{HA}]}$. I ...