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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Effect of an inert gas on steam vapor pressure at equilibrium

Suppose we have a closed container with mobile walls, so it will change its volume in order to equal the external pressure(constant) to the internal pressure. This container has inside it a liquid ...
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13 views

Vapour Pressure and Equilibrium

A liquid in its equilibrium with its vapour is in a sealed container at a fixed temperature. The volume of the container in suddenly increased. a) What are the changes in the rate of evaporation and ...
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23 views

Finding OH- concentration given the H+ concentration - diverse methods

There was this exercise which asked to find the OH- concentration given the H+ concentration, i firstly calculated the pH as -log[H+], did 14-pH to find the pOH and then did 10^(-pOH) to find the ...
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24 views

Can a non-equilibrium reaction be reversed by adding enough energy? [on hold]

I read that a major reason not all reactions are in equilibrium is because the reverse reaction requires a high activation energy, thus collisions between atoms/molecules of products are in-effective ...
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Determine overall activation energy [on hold]

For a parallel reaction, A-B E=150kj/mol A-C E=80kj/mol A-D E=30kj/mol Mole percentage of B,C,D after one hour was found out to be 10,25,15 respectively. Determine the overall activation ...
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13 views

how to calculate the new value of equilibrium constant after doubling the volume of vessel [closed]

The equilibrium concentrations of A and B for the reaction A(g) + 2 B(g)=== C(g) are 3M and 4M respectively.when the volume of vessel is doubled and the equilibrium is allowed to re establish the ...
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53 views

Can equilibrium be reached in a non-reversible chemical reaction?

Can chemical equilibrium only be achieved in a reversible process? I have only seen equilibrium in processes that are reversible so I was wondering if it were possible in reactions that are not ...
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20 views

Equilibrium Question from USNCO local exam 2016

IBr(g) is in equilibrium with I2(g) and Br2(g) at 150 ºC: 2 IBr(g)<-----> I2(g) + Br2(g) K = 8.50*10^-3 Initially, a closed vessel at 150 ºC has a partial pressure of IBr of 0.350 atm and ...
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21 views

Ignoring the difference of concentrations of reactants. Equilibrium

Recently at school, while studying equilibrium we learned that in problems where the initial concentrations of reactants and the equilibrium constant are given, there is a special formula to determine ...
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29 views

Solubility of silver acetate in the presence of nitric acid

What will be the effect on the solubility of $0.1\ \mathrm{mol}$ of $\ce{CH3COOAg}$ in presence of $1\ \mathrm{l}$ of $0.1~\mathrm{M}\ \ce{HNO3}$ solution? $$K_\mathrm{sp} (\ce{CH3COOAg}) = 10^{-...
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64 views

Calculate the pH of Na2CO3

Given information: $K_\mathrm{a}(\ce{H2CO3}) = 4.3 \times 10^{-7}$, $K_\mathrm{a}(\ce{HCO3-}) = 4.8 \times 10^{-11}$, ${{\ce{[Na2CO3]}=0.20\ \mathrm{M}}}$ This was a question in an exam and I'm ...
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31 views

Equilibrium Constant Explained

I'm not interested in a simple telling of what the properties of the equilibrium constant are and how to use them. I'm more hoping for an explanation of where it came from/how it might be possible to ...
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26 views

Calculating Ratio of Stability Constants

Solution I contains a mixture of $\ce{FeCl2}$ and $\ce{FeCl3}$, and solution II contains a mixture of $\ce{K4Fe(CN)6}$ and $\ce{K3Fe(CN)6}$. The concentrations of iron-containing species satisfy the ...
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65 views

Decomposition of CaCO3 in a sealed vessel

For the equilibrium $$\ce{CaCO3(s) <=> CaO(s) + CO2(g)}$$ $\Delta H^\ominus = 178\ \mathrm{kJ\ mol^{-1}}$ and $\Delta S^\ominus = 160\ \mathrm{J\ mol^{-1}}$. I'm asked to suppose that $1\ \...
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81 views

Difference between freezing point and melting point

I do not understand why for mixtures freezing point is lower than melting point. Are not the two representing the same equilibrium between solid and liquid which we are approaching from two different ...
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154 views

Why is EDTA most soluble at a pH 8? (addition of NaOH)

Although Wikipedia says that EDTA is a very soluble salt, preparing a solution (.5M) is a pain in the neck. It takes a lot of time and still doesn't dissolve. Although addition of a few drops of NaOH ...
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30 views

Chemical equilibrium and Le Chatelier Braun for ammonia production

In the book of Chemical, biochemical and engineering thermodynamics 4th edition from Stanley I. Sandler (Wiley, 2006), there is a problem about the ammonia producing reaction at page 770. 13.17 The ...
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Chemical Equilibrium - Diluting a system by adding water

Adding water to an aqueous system, the system becomes diluted and responds by favoring the reaction with the most amount of ions in solution. But apparently, adding $3\ \mathrm{mL}$ of water to $\ce{...
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49 views

Phenolphthalein as a indicator for the titration of benzoic acid

Question: Justify the use of phenolphthalein $(\mathrm{p}K_\ce{in}=9.4)$ as a indicator for the titration of benzoic acid $(K_\mathrm{a}=6.3\times 10^{-5})$ with $\ce{NaOH}$. My attempt: I can ...
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23 views

Why does changing the dilution of an aqueous equilibrium shift the equilibrium?

Say we have the equilibrium $$\ce{A_{(aq)} + 2B_{(aq)} <=> C_{(aq)} + D_{(aq)}}$$ meaning the formula for the equilibrium constant is $$\ce{K_{c} = \frac{[C][D]}{[A][B]^2}}$$ My understanding is ...
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30 views

Why is the water dissociation constant valid for acid/base solutions?

The water dissociation constant was first defined with respect to dissociation of water into hydroxyl and hydronium ions. How then can one say that it is valid for an acidic solution, that is, even in ...
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277 views

What does curly brackets {} mean?

I learned that square brackets ex: [H$_2$O] can be used to denote the concentration of water molecules in a fluid. The notation used much in equilibrium problems and such. However, sometimes I have ...
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1answer
29 views

Acid - Base Equilibrium

Suppose we had a closed system proceeding according to, $$\ce A +2\ce B \rightleftharpoons 2 \ce C$$ And that three experiments produced the following concentration data. Experiment 1: \begin{...
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43 views

What is the use/importance of the equilibrium constant Kc [closed]

I understand what the equilibrium constant is, however when reading in my textbook it has occurred to me that I do not understand what it's actual use/importance is. One specification in my syllabus ...
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60 views

What is the difference between the equilibrium position and the equilibrium constant?

I used to think that the equilibrium constant was a quantitative measure of the equilibrium. However, changing concentration and pressure in a system at equilibrium that shifts the equilibrium doesn't ...
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37 views

Temperature in the Gibbs Free Energy equation

My professor gave us 2 different ways to calculate this problem. I did it using the Clausis-Clapeyron equation. However, I don't quite get the second method because I thought that if the change in ...
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19 views

Does reaction quotient Q take into account pure solids and liquids?

I understand that the equilibrium constant does not take into account the concentrations/ pressures of pure solids and liquids. How about the reaction quotient? In the following reversible reaction, ...
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34 views

NaCl Electrolysis - Dilute vs Concentrated - Nernst Equilibrium

Interested to know if there is a critical concentration at which $\textrm{Cl}^{-}$ will oxidise over H$_2$O and if this can be determined using the Nernst equation. That is, obviously if $[\textrm{Cl}...
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39 views

shifting of equilibrium

Does it mean that if one side of a reaction is favoured, the reaction will shift to the other side? As I was reading up on the van't Hoff equation, it says that an increase in temperature of an ...
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27 views

Does the activity product decrease with increasing ionic strength?

I have a question regarding what happens to the solubility of $\ce{CaSO_4}$ or the rate that $\ce{CaSO_4}$ will dissolve when we add $\ce{NaCl}$ to the solution: $\ce{CaSO_4}$ will dissolve into $\...
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26 views

Equilibrium constant in a reaction with stoichiometric coefficient 1/2

I have a doubt. I calculated the equilibrium constant for the follow reaction at 298 K $CH_4(g) + 1/2 S_8 (s) \leftrightarrow CS_2 (l) + 2 H_2S(g)$ I reached to $1.65 \times 10^{-9}$. However my ...
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Measuring the Kc of equilibrium between NO2 and N2O4 [closed]

I'm trying to measure the $K_c$ of the equilibrium reaction $$\ce{2 NO2 (g) <=> N2O4 (g)}$$ in different temperatures. How would I do this do this in a normal school laboratory? I was thinking ...
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23 views

How to evaluate standard enthalpy, standard entropy and standard free energy in a temperature different that 298K

A question is asking me to calculate the equilibrium constant of a given reaction of gases at 373 K. My immediate thought was to think about van't Hoff equation: $K_p=e^{\frac{-\Delta G^0}{RT}}$ ...
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1answer
43 views

Percent composition by volume of the reaction H2 + Br2 <=> 2HBr

For the reaction $\ce{H2(g) + Br2(g) <=> 2HBr(g)}$ at a certain temperature, $K=1$. Determine the composition (in per cent by volume) of the equilibrium reaction mixture if the initial mixture ...
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Combining acid dissociation constants to determine pH of diprotic acid

If I have a diprotic acid with $K_{\mathrm{a1}}$ and $K_{\mathrm{a2}}$ as the acid dissociation constants, why can't I calculate the final $\mathrm{pH}$ using $K = K_{\mathrm{a1}}\cdot K_{\mathrm{a2}}$...
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24 views

How can you change the proportions of reactants and products at equilibrium if Le Chatelier's principle is occurring?

For example, how could you make a buffer with equal concentrations of acid and conjugate base? If you add more conjugate base, it will shift the equilibrium to form more acid, which will keep the ...
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Why don't we take into account the auto-protonation of water when measuring its concentration?

When we calculate the concentration of water at $ 25~^\circ\rm C $, why don't we assume dissociation of water at this temperature? $$\ce{H2O <=> H+ + OH-}$$
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Why do acids mix in water faster than bases?

I have $100\ \mathrm{L}$ of water in a tank with an mixer inside and want to know how fast the tank mixes at a given rpm-setting. I am adding $50\ \mathrm{mL}$ of $2\ \mathrm{N}\ \ce{HCl}$ and see ...
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287 views

How is volatility useful in the production of acids?

Sulfuric acid because of its low volatility can be used to manufacture more volatile acids from their corresponding salts. How does volatility affect the production of acids? Isn't it that sulfuric ...
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44 views

What's the Kp value?

A mixture of $1\ \mathrm{g}$ of $\ce{H2(g)}$ and $1.06\ \mathrm{g}$ $\ce{H2S(g)}$ in a $0.5\ \mathrm{L}$ flask come to equilibrium at $1670\ \mathrm{K}$. At equilibrium, there are $8\times10^{-6}\ \...
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pH of a double buffer

If $1,2,3,4$ moles of $\ce{H3PO4}$,$\ce{NaH2PO4}$,$\ce{Na2HPO4}$ and $\ce{Na3PO4}$ respectively are mixed together to form an aqueous solution of $1$Litre , resulting $\ce{pH}$ is? This question has ...
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The behaviour of Ag3PO4 in solution

To a 1L flask, we add $4.1900\mathrm{g}$ ($0.01001\ \mathrm{moles}$) of $\ce{Ag3PO4}$, then fill it up with water. Knowing the following constants, we are asked to find the concentration of all ...
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1answer
153 views

Relationship between pKa and pKb

The $\mathrm{p}K_\mathrm{a}$ of $\ce{NH3}$ is $38$. Does it stand for the following equilibrium: $$\ce{NH4+ <=> NH3 + H+} \tag{1}$$ With $K_\mathrm{a} = 10^{-38}$ for reaction $(1)$, indicating ...
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227 views

Is it possible for one of reactants to deplete before achieving equilibrium

Consider the following reaction where $\ce{A}$ & $\ce{B}$ reacts to produce $\ce{C}$ & $\ce{D}$. $$\ce{ A(g) + B(g) <=> C(g) + D(g)}$$ Is it possible for $\ce{A}$ or/and $\ce{B}$ to ...
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Equilibrium Problem Involving Solids: Faulty?

I am convinced that this is a faulty problem: $\ce{2 Cu + S -> Cu2S}$ For the reaction above, $\Delta H$, $\Delta S$, and $\Delta G$ are all negative. Which of the substances would ...
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2answers
37 views

Why is iron(II) fluoride thermodynamically favorable when dissolved in acid?

I am reviewing for the AP Chemistry test, and the question is this $$ \ce{FeF2(s) <=> Fe^2+(aq) + 2F^- (aq) } \quad K_1 = 2\times 10^{-6} $$ $$ \ce{F- (aq) + H+ (aq) <=> HF(aq)} \quad ...
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Apparent solubility of Ag2C2O4 in a buffer solution

We take the following quantities and mix them together: $20\mathrm{mL}$ solution of $\ce{AgNO3}$ $0.001 \frac{\mathrm{moles}}{\mathrm{dm^3}}$ $20\mathrm{mL}$ solution of $\ce{H2C2O4}$ $0.200 ...
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27 views

Spontaneous and Favoured Chemical Reactions

I have some problems in understanding what is the difference between a reaction which is spontaneous and a reaction which is termodynamically favoured. I'm looking at the equation of Gibbs Free Energy:...
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61 views

The effect of reactant concentration on when equilibrium is established

Take the equation $$\ce{A(g) <=> B(g)}$$ where the reaction is first order with respect to A. The rate law is thus $$\frac{\mathrm d[\ce{A}]}{\mathrm dt}=-k[\ce{A}]$$ Say you run the reaction, ...
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59 views

How to find deltaG when given the equilibrium constant and temperature?

For the reaction, $$\ce{N2O4(g) <=> 2NO2(g)}$$ the equilibrium constant in terms of concentration, $K_c$, at $100~^\circ\rm C$ is $0.36$. What is ${\rm\Delta} G$? I used the equation $${\rm\...