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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How can a dilute acid dissociate more than a concentrated one? (Ostwald dilution law)

According to Ostwald's dilution law, the degree of dissociation of an electrolyte is inversely related to the concentration of it. $$ \alpha = \sqrt{\frac{K_a}{C}} $$ This means that a dilute acid ...
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Obtaining activity coefficients of conjugate acids of some common carboxylic acid molecules

Recently, I have been wondering about justifying the notion on how some common acids (e.g. carboxylic acids) are themselves weaker bases than water to the point that we don't usually consider them to ...
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Van't Hoff Equation with changing Enthalpy

Is there a way to derive a modified van 't Hoff equation if we can't make the assumption that $\Delta H_\mathrm{r}$ doesn't change? We know that $\mathrm{d} \ln K/\mathrm{d}T = \Delta H_\mathrm{r}/(...
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What kind of 'product' is the 'product' in 'ionic product of water'?

My language has different words for product (=the result of a process) and product (=the sum of multiplied quantities), so I need to know the right meaning to choose the right word. Which of the ...
PrettyHands's user avatar
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What is the relationship between equilibrium concentrations in two similar experiments?

Two experiments were performed involving the following equilibrium. The temperature was the same in both experiments. $$\ce{H2 (g) + I2 (g) <--> 2HI (g)}$$ In experiment A, $\pu{1.0 M}~\...
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When removing a reactant and equilibrium shifts left, doesn't this make an excess of the 2nd reactant, forcing equilibrium back to the right?

In the reaction:$$\ce{Ca^{2+}(aq) + ^-OOC-COO^- <=> Ca(OOC-COO)(s)}$$ If $\ce{Ca^{2+}(aq)}$ is removed, the reaction shifts to the left to produce more $\ce{Ca^{2+}(aq)}$ to compensate. But ...
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When pH increases, does the effect of increased [OH-] or reduced [H+] control precipitation of CaC2O4

The image below shows how oxalic acid dissociates and forms calcium oxalate ($\ce{CaC2O4}$ or $\ce{Ca(OOC-COO) as written below}$). When the pH increases, does this result in more or less $\ce{Ca(OOC-...
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Is following graph is of a dibasic or monobasic acid?

Is the above graph is of a dibasic or monobasic acid? There is slight hint of it being of dibasic around 15. But is it enough to conclude ? I am confused.
mathemather's user avatar
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Do the units of the law of mass actions convey any meaning?

Since the number that you end up with, when calculating the value of the law of mass action for a given reaction often also has a unit, I was wondering if there is any physical meaning to this given ...
Christian Singer's user avatar
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How to determine the temperature dependence of equilibrium constants?

Given $K_c=2.8\times10^2$ at $727~^\circ\mathrm{C}$ for $$\ce{ 2SO2 + O2 <=> 2SO3},$$ calculate $K_c$ and $K_p$ when 8 grams of $\ce{SO2}$ result in 0.32 grams of $\ce{O2}$ forming at ...
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How to know when dissolution is complete?

In a given solubility equilibrium, I know that if $ Q >K_s$, then the salt will precipitate until $ Q =K_s$. If $ Q <K_s$, however, would the precipitate dissolve until $ Q =K_s$ too?
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Why is Ka constant when volume is increased?

The following graph shows $\ce{Ka}$ vs ${V}$ (Volume) at constant temperature, as ethanoic acid is diluted: However, I thought it would instead produce the following graph (see below). $\ce{Ka=[...
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How to determine the minimum pH at which iron(III) hydroxide dissolves completely?

Knowing $K_\mathrm{s} = 6\cdot10^{-38}$ for $\ce{Fe(OH)3}$ in neutral solutions, calculate the minimum pH of an acidic solution in order to completely dissolve $\pu{10 mg}$ of $\ce{Fe(OH)3}$. Data: $V ...
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About the equilibrium of a flowing reaction

Imagine to have a tube (to make a reactor simple) inside which a chemical reactions take place and reactants are constantly fed so overall can be considered in steady-state conditions. Just to pick ...
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le chateliers principle

One of le chateliers principle is effect of concentration change : When the concentration of any of the reactants or products in a reaction at equilibrium is changed , the composition of ...
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Can the enthalpy change of a reaction be changed, and if so, will this affect the value of the equilibrium constant?

In the case of an arbitrary equilibrium reaction, is it possible to change the absolute enthalpy of the final products, thus the reaction enthalpy change? For example, say pH affects the charge ...
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How do we know the concentration of hydroxide ions in this derivation?

In the derivation of the pH of a solution of a salt prepared from a weak acid and strong base, I used two equilibrium reactions: $$\ce{ CH3COOH(aq) + H2O(l) <=> H3O+(aq) + CH3COO-(aq)} \qquad ...
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Do perfect gases react when placed in a container whose volume can vary?

Suppose that $n$ moles of four generic perfect gases are made to react in a container, whose volume can vary, at a constant temperature and pressure, according to the formula $$\ce{A(g) + B(g)<=&...
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Equilibrium Constant in terms of Molar Concentration of Gases versus Equilibrium Constant

Suppose the gases involved in a reaction behave as real gases with significant intermolecular attractions. I just learned that $$K_c(RT)^{\Delta n_r} = K$$ Would the value of Kc calculated from the ...
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How do I calculate the number of molecules in an equilibrium depending on a change in the equilibrium constant? [closed]

Consider 1000 molecules of $\ce{A}$ and 1000 molecules of $\ce{B}$ in a eucaryotic cell. The concentration of both will be about $\pu{10^-9 M}$. If the equilibrium constant $K$ for $\ce{A + B <--&...
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When can I use concentrations instead of activities in equilibrium calculations?

To calculate an equilibrium constant, it is said that you should actually use activities $a_i$ instead of concentrations $c_i$. But it is also said that within a certain range, you can use ...
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How to derive if the reaction is endothermic or exothermic based on rate constants at different temperatures? [closed]

Listed in the table are forward and reverse rate constants for the reaction $$\ce{2NO (g) <=> N_2 (g) + O_2 (g)}$$ \begin{array}{ccc} \text{Temperature}/\pu{K} & k_f/\pu{M^-1s^-1} & ...
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How can I calculate the percentage of dissociated dinitrogen tetroxide?

When $\pu{36.8 g}$ $\ce{N2O4(g)}$ is introduced into a 1.0-litre flask at $\pu{27 °C}$ the following equilibrium reaction occurs: $\ce{N2O4(g) <=> 2NO2(g)}$; $K_p = 0.1642~\mathrm{atm}$. Find ...
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What active mass actually is? [duplicate]

I'm so much confused about what active mass actually is, my text book states that, active mass is a dimensionless quantity, but for our convenience and purposes, we take it with dimensions of molarity,...
Adesh Tamrakar's user avatar
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Derivation of relation between acid and base equilibrium constants

While deriving the relation between $K_a$ and $K_b$ in ionic equilibrium topic, say I take an example of $$ \ce{NH4+ + H2O -> NH3 + H3O+} \tag{1}\label{1} $$ The $K_a$ of this reaction is: $$ \...
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Can the equilibrium constant be equal to 0? [duplicate]

Can $K_\mathrm{eq}$ (not $Q$) be equal to $0$? My book says: $K_\mathrm{eq}$ is always positive because the concentration at equilibrium, small or large, are always positive. But it says $Q$ can ...
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Why can't a reaction go to completion?

What is the reason for why an exergonic reaction would still have some remaining reactants (or an endergonic reaction to have any products)? The explanation given on this page (see Chemical reactions ...
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Activity of Materials in Equilibrium constant

I learnt that we use activity to define the equilibrium constant . But while calculating the equilibrium constant we plug in their concentration instead of activity . For a general reversible ...
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Finding the value of pressure equilibrium constant

Question: A rigid vessel containing only $\ce{NO2(g)}$ is heated to $\pu{337^{ \circ}C}$ and allowed to come to equilibrium according to the following reaction: $$\ce{2NO2 <=> 2NO + O2}$$ ...
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Instantaneous enthalpy and entropy change of reaction as equilibrium is established

Can we calculate instantaneous difference between enthalpy and entropy of product and reactants of a reaction as the reaction proceeds towards equilibrium? Ex: $\ce{R<->P}$ reaction, at some ...
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Will this SN1 reaction result in an equilibrium situation?

I'm trying to prove the rate law of an $S_N1$ reaction by measuring the rate of it, when I vary the concentrations of my reagents. However, I believe the reaction of the experiment I have designed ...
Saul McShane's user avatar
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Basic behaviour of bromide ion with sulfuric and phosphonic acid

I  recently came across these two reactions: $$\begin{align}\ce{2KBr + 3H2SO4 &-> 2KHSO4 + Br2 + SO2 + 2H2O}\tag{1}\\[0.6em] \ce{KBr + H3PO4 &-> KH2PO4 + HBr}\tag{2}\end{align}$$ I ...
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Arrhenius Acid-Base

According to the Arrhenius concept of acid, "an acid is a substance that, when dissolved in water, increases the concentration of hydronium ion. Is $\ce{HSO4-}$ in the following chemical equation an ...
alend ahmed's user avatar
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When volume decreases and the product has less moles than reactants, why is there no increase in the reaction quotient?

Assume a reaction: $$\ce{CO + Cl2 <=> COCl2}$$ My textbook says that a decrease in volume will result in the reaction quotient being less than the equilibrium constant. Why is that? With a ...
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Ammonium is a weak acid but isn't it considered a strong conjugate acid as a salt's ion? [duplicate]

I'm learning about salt hydrolysis in school and this just jumped out at me. How can $\ce{NH_4^+}$ be both a weak acid and a strong conjugate acid? Since $\ce{NH_4^+}$ is a weak acid it has a strong ...
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Calculating acid dissociation constant for polyprotic acids

I'm confused with $K_{a1}$ and $K_{a2}$ for a polyprotic acid and how they are found, consider the following: A solution of $1 M$ of $\ce{H2SO4}$ would yield $1 M$ of $\ce{H3O+}$ and $\ce{HSO4-}$ ...
alend ahmed's user avatar
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When ∆Suniv = zero, does the concentration of reactant equal the concentration of product?

It is my understanding that when ∆Stot / ∆Suniv = 0 then the reaction does not occur, the position of equilibrium is not shifted in a specific direction. However, does this imply that [reactants] = [...
Noah Harrison's user avatar
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At equilibrium are the rates of the forward and backward reactions equal to zero?

At equilibrium, the concentrations do not change with time. So, is it true that the rates of the chemical reactions are zero at equilibrium? Wikipedia says that they are not zero. Why is this?
Krishna Kanna's user avatar
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Solving for H+ given dissociation of weak acid, c and Ka Can the quadratic equation yield two nontrivial solutions?

For example, if a question asks for $[\ce{H+}]$ of a $0.100~\mathrm{M}$ solution of picric acid (monoprotic), given that its $K_\mathrm{a}$ at the system temperature is $4.2 \times 10^{-1},$ following ...
Jack Pan's user avatar
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Le Châtelier's Principle and heat

Consider the following reaction at equilibrium. $$\ce{A->B}, \Delta H < 0 $$ Suppose I increase the temperature. Now, quite a few people would invoke Le Châtelier's Principle and say that since ...
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Molarity of solids and liquids in equilibrium constant expression [duplicate]

Why is the molarity of pure liquids , solids and excess solvent taken 1 in the equilibrium constant expression?
Jasgeet Singh's user avatar
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2 answers
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Calculating the dissociation constant of one acid in a mixture

A solution contains $\pu{0.09 M}~\ce{HCl}, \pu{0.09 M}~\ce{CHCl2COOH}$ and $\pu{0.1 M}~\ce{CH3COOH}$. The $\mathrm{pH}$ of the solution is $1$. Given that the $K_\mathrm{a}$ of acetic acid is $10^{-5}$...
Akshat Batra's user avatar
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Why can one product in an equilibrium system not be produced without the other? [closed]

I performed an experiment where $\ce{CuSO4 (aq)}$ reacted with $\ce{NH3 (aq)}$ in one test tube, and in the other, $\ce{CuSO4 (aq)}$ reacted with $\ce{NH3 (aq)}$ and $\ce{NaOH (aq)}$. I know two ...
Savannah's user avatar
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Why does increasing the available surface area of a pure solid not effect equilibrium?

Take a reverseable reaction of a gas and a solid, $$\ce{A(g) + B(s) <=> C(g)}$$ The rate of the forward reaction will depend on the surface area of the solid available. If I take that system at ...
Random Hero's user avatar
1 vote
1 answer
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Dynamic equilibrium of gases

$$\ce{2SO2(g) + O2(g) <=> 2SO3(g)}$$ The equilibrium constant for the reaction above is $0.13$ at $\pu{830^\circ C}$. In one experiment $\pu{2.00 mol}$ of $\ce{SO2}$ and $\pu{2.00 mol}$ of $\...
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Calculation of equilibrium constant given the reaction temperature [closed]

I have only a chemical equation, like: $$\ce{N2 + 3H2 <=> 2NH3}$$ How can I calculate the value of equilibrium constant from only this equation. Provided temperature is $\pu{298K}$. I can use ...
S R Maiti's user avatar
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Effects of inert gas on heterogenous equilibrium

What is the effect of the presence of an inert gas on a reversible reaction that was in more than one phase, such as a decomposition reaction? If a solid or liquid or compound in aqueous solution ...
user36621's user avatar
3 votes
1 answer
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How do you calculate the equilibrium constant with the absorbance of a substance and the absorbance constant?

When given the equation: $$\ce{Fe^3+_{(aq)} + SCN^-_{(aq)} <=> FeSCN^2+_{(aq)}}$$ How do you calculate the equilibrium constant when given the slope of the absorbance vs concentration graph ($\...
Alexander's user avatar
1 vote
2 answers
633 views

Overall equilibrium expression for competitive equilibria

I have a case where I have two reactions that depend on a common reactant. The reactions can be written as: I) $\ce{A + B <=> AB}$ II) $\ce{A + C <=> AC}$ We can thus write equilibrium ...
Marcel's user avatar
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Is equilibrium potential for K+ always ~-90 mV?

Equilibrium potential is the difference in charge relative to the inside of the cell. -90 mV means that the inside of a cell is more negative than the outside. However when you talk about equilibrium ...
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