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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31 views

Does a weak buffer solution still maintain a mostly steady pH if the acid or base load it has to buffer is small?

I need to buffer the $\mathrm{pH}$ of a solution to $3.0$ using a citrate buffer. I found a recipe to make a buffer solution that would use $82\%$ of $0.1\,\mathrm M$ citric acid (monohydrate) and ...
4
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1answer
40 views

In equilibrium, if bonds are constantly being created and broken, where does the energy that does so come from?

I'm a student who recently learned about equilibrium and how it is not a state where nothing is made, but rather, a state where the product is decomposing at the same rate as the reactants are ...
2
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1answer
37 views

Why is the equilibrium constant defined that way intuitively? for $\ce{ aA + bB <=> cC + dD }$

Suppose we have chemical equation $$\ce{ aA + bB <=> cC + dD }$$ then equilibrium constant is defined $$K=\frac{[C]^c[D]^d}{[A]^a[B]^b},$$ but why don't we define it as ...
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0answers
13 views

Change of concentration in an equilibrium

I understand the fact that if you change the concentration of a pure solid or liquid in an equilibrium reaction, nothing happens because concentration = density which is constant in liquids and solids ...
0
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1answer
48 views

What is the effect of adding HCl on a certain solution at equilibrium?

If we have $$\ce{CH3COOH + H2O <=> CH3COO- + H+}$$ what is the effect on acetate ions when adding each HCl and NaOH to the solution? (State why according to Le Chatelier's principle) ...
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22 views

What are the methods used to measure the concentrations of these anions?

Chromate and dichromate anions has the following equilibrium in acidic solution: $$\ce{2CrO4^2- + 2H3O+ <=> Cr2O7^2- + 3H2O}$$ How can one experimentally measure the concentration of each ion ...
3
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1answer
62 views

Alternate solution for finding concentration in equilibrium

This question is still waiting for a better alternate answer. If you can add it then your answer can be chosen as accepted I came across a question yesterday A container contains three gases. ...
1
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1answer
22 views

What would Kp be if there is no gas reactant

What would $K_\text{p}$ be if there is no gas reactant but the reaction produces gas. I found something confusing: $$K_\text{p}=\frac{P_\text{gas product}}{P_\text{gas reactant}}$$ If there is no gas ...
3
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2answers
35 views

Resultant temperature of mixture

**Question: ** There are 2 flasks of equal volume, connected by a narrow tube of negligible volume, filled with nitrogen gas. When both are immersed in boiling water, the gas pressure inside the ...
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0answers
18 views

How can collission theory of chemical reaction and Law of mass action be connected?

Collision theory is a theory that qualitatively explains how chemical reactions occur and why reaction rates differ for different reactions The collision theory states that when suitable ...
11
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1answer
119 views

Acidity of HCl in Acetic Acid

A question asked to find the pKa of $\ce{HCl}$ in acetic acid. The equation of $\ce{HCl}$ disassociating in water is: $$\ce{HCl + CH3COOH \leftrightharpoons CH3COOH2+ + Cl-}$$ I predicted that the pKa ...
2
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1answer
49 views

Titration Question

Problem: A solution of an unknown weak acid of unknown concentration was titrated with a solution of a strong base of unknown concentration. During the titration, the pH after adding $2.00$ mL of the ...
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0answers
20 views

Charge:ionic radius ratio

can someone please explain what the charge to ionic radius ratio of a metal hydroxide would mean for its solubility. As in would there be a trend e.g. as the ratio gets larger the solubility product ...
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0answers
6 views

Equilibrium saturation/depostion rate calculation

I found the Knudsen/Langmuir equation for calculating the sublimation rate of a solid. If I have a closed system, once the vapor reaches the saturation pressure, the solid will continue sublimating ...
3
votes
0answers
27 views

How to prove that the forward and reverse reactions have the same rate at equilibrium?

I was trying to answer a question from Zumdahl and Zumdahl's Chemistry textbook which asks me to show that the rate constant K is related to the forward and reverse reaction constants: ...
1
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0answers
29 views

How to know when subscripts refer to charges or not

My question is very easy. Sometimes to determine to charge of a compound you multiply the charge by the number of ions you have of that element. But sometimes it seems as if you don't do it this way. ...
2
votes
1answer
31 views

Why are Kc and Kp interchangeable in the free energy-equilibrium equation? [duplicate]

In this equation that relates Standard free energy and the equilibrium constant: $\Delta Gº=-RT \ln K_{eq}$ My textbook (and my teacher) say both $K_p$ (constant related to pressure) and $K_c$ ...
1
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1answer
33 views

Possible approximations in complex equilibrium

If I have the following equilibrium: $$\ce{Cu^2+ + 4NH3 <=> Cu(NH3)4^2+}$$ Given an initial concentration of $\ce{Cu^2+}$ ($C_\ce{Cu}$) and an initial concentration of ammonia $C_{NH_3}$, the ...
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3answers
1k views

Why is the Haber process carried out at such high temperatures?

On a large scale, ammonia is prepared via the Haber process: $$\ce{N2(g) + 3H2(g)->2NH3(g)} \qquad \Delta _\mathrm{f}H^\circ = -46.1~\mathrm{kJ \cdot mol^{-1}}$$ The optimum conditions for the ...
0
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1answer
29 views

What is meant by a reaction favours one side?

I frequently see in textbooks the phrase, a reaction favours the left/right side, but don't know what this means. Does this mean the equilibrium shifts to one side?
3
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1answer
65 views

What are the correct equilibrium arrows?

I was recently subject to some atrocious teaching. One of the gems that found me was the equilibrium arrow usage. I am accustomed to write $\ce{<=>}$. Yet, the entire class had to use ⇆ ...
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2answers
33 views

Enthalpy change and equilibrium

I don't understand why enthalpy change won't change at an equilibrium? The reason I ask this is because of this question: At first I thought the answer is C, but I realised that the amount depends ...
2
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1answer
123 views

Why does a dynamic equilibrium exist?

We know that at equilibrium Gibbs free energy is minimum. We also know that at equilibrium both forward and reverse reactions occur simultaneously, and we also know that for a reaction to be ...
3
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0answers
34 views

Active mass,Pressure and concentration

The concentration is connected to the activity via $$a(\ce{A})= \gamma_{c,\ce{A}}\cdot{}\frac{c(\ce{A})}{c^\circ},$$ where the standard concentration is $c^\circ = 1\:\mathrm{mol/L}$. At reasonable ...
3
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1answer
58 views

Why at constant pressure and temperature Gibbs energy change of a process can be negative?

$dG < 0$, for a spontaneous reaction at constant Temperature $T$ and Pressure $P$, this means that at contant $T$ and $P$, $dG$ can be negative $dG = VdP -SdT$, this means that at constant $P$ ...
4
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1answer
54 views

Formation of a stable hydrate

Question: Which of the following does not form a stable hydrate? I think they mean nucleophilic addition of water. For compound (C), on reaction with water, the product formed is The ...
4
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1answer
150 views

Which has maximum entropy

Which state has a higher entropy — the liquid–gas equilibrium or the gaseous state? I have learned that at equilibrium the entropy is maximised. But I also learned that the gaseous state has the ...
3
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1answer
33 views

Ostwald Law of dilution makes no sense

According to wikipedia the Ostwald's dilution law says that for a weak acid $K_{d}={\cfrac {[A^{+}][B^{-}]}{[AB]}}={\frac {\alpha ^{2}}{1-\alpha }}\cdot c_{0}$ when I read the derivation of it ,I ...
1
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1answer
29 views

Question related to Indicators

Ram can see the purple colour of an acidic indicator below pH = 5.5 only and the blue colour only above pH = 8.5. How many times that of acidic form must the concentration of the basic form at least ...
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0answers
33 views

How to Calculate Concentrations when Dissolving Two Salts

Some solid silver bromate was dissolved together with solid silver acetate what would be the highest achievable pH? Data $\mathrm{K_{sp ~\ce{(AgBrO3)}}} = 5.38 \times 10^{-5}~~~~~~~ ...
3
votes
1answer
21 views

Writing equilibrium expressions with aqueous species

If we have the reaction: $$\ce{A +BC_{(aq)} <=> D}$$ where $\ce{A}$ and $\ce{D}$ are generic compounds (neither is pure solid nor pure liquid) and $\ce{BC}$ is an ionic compound dissociated in ...
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0answers
27 views

Are open system phase transitions physical equilibriums?

I have been told that phase transitions=physical equilibriums. How can phase transitions be physical equilibriums? For example, if you have liquid water going into gas phase, doesn't delta G have to ...
3
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2answers
74 views

What is the purpose of finding log k?

I understand that k alone is the equilibrium constant and know how to find this number or when given it I can take the log of this number, but what is the purpose of this number? What does the log of ...
0
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1answer
71 views

Determining the nature of common pH indicators (methyl orange) using Le Chatlier's principle

I got some good information about this topic yesterday, and I understood what I was told, but I have come up with a specific way of phrasing the problem I'm having. It is slightly different than ...
0
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0answers
18 views

Pressure equilibrium constant units in calcium carbonate decomposition

For $Ca(OH)_2$ decomposition the expression for the equilibirium constant is $K_p = p_{H_2O}$ where, $p_{H_2O}$ denotes the partial pressure of water. I have an exercise where I am asked to ...
0
votes
1answer
43 views

Why is the ionic product for water $10^{-14}$? [closed]

Why is the reference value of $K_w=10^{-14}\ \mathrm{M}^2$, such that $[\ce{H+}]= 10^{-7}\ \mathrm{M}$ and $[\ce{OH^-}]= 10^{-7}\ \mathrm{M}$ for pure water at $20\ ^\circ \mathrm{C}$? For example, ...
9
votes
2answers
194 views

Reason behind Le Chatelier's principle

I understood Le Chatelier's principle perfectly but my question is why? Why should a system try to reverse any change that has been done to it? I understand equilibrium constant, mole concept and ...
0
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0answers
53 views

How to find K value for the reaction?

Problem: Given that the $K_\mathrm a$ for $\ce{HOCl}$ is $\mathrm{3.53 \times 10^{-8}}$, calculate the $K$ value for the reaction of $\ce{HOCl}$ with $\ce{OH-}$. a. $3.53 \times 10^6$ b. $3.53$ ...
3
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2answers
48 views

Dissociation of benzoic acid

Benzoic acid is a weak acid, which means that it does not completely dissociate in water. I know that the dissociation equation of Benzoic acid is: $$\ce{C6H5CO2H <=> H+ + C6H5CO2-}$$ The ...
5
votes
2answers
97 views

Why is water not part of the equilibrium constant?

In the acid base reaction $$\ce{NH4+ + H2O <-> NH3 + H3O+}$$ the acidity constant, which is a relation between concentrations is given by $$K_{\mathrm{a}}=\ce{\frac {[NH3] \cdot [H3O+]}{ ...
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votes
2answers
55 views

le chatelier's principle pressure

I know that when we increase the pressure on any system the reaction shifts to the less number of moles side , But what about th volume ? Pressure and volume are inversely proportional so if we ...
0
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1answer
59 views

Increase in Yield of products in an exothermic reaction

Given an exothermic reaction $\ce{N2 + 3H2 -> 2NH3}$ (which was initially in equilibrium). The temperature is then increasing with time. I am supposed to predict the yield of ammonia with time. ...
10
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4answers
496 views

What is the real difference between ∆G and ∆G°?

In Brady's Molecular Nature of Matter, I read that $\Delta G^{\circ}$ is $\Delta G$ at $25~^\circ\mathrm{C}$. But later, it gives a value for $\Delta G^\circ$ at another temperature. What is the ...
6
votes
2answers
156 views

Short Cut Method to Calculating pH of Polyprotic Acid?

I am doing the following question: Calculate the pH of a $4.00\ \mathrm{mol\ L^{-1}}$ solution of citric acid. $\mathrm{pK_{a1}} = 3.09~~~~~ \mathrm{pK_{a2}} = 4.75~~~~~ \mathrm{pK_{a3}} = 6.40$ ...
2
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1answer
38 views

Equilibrium and Completeness of Reaction [duplicate]

In class we are currently learning about equilibrium and Le Chateliers principal. The principal makes sense but seems contrary to some other concepts. For example, using stoichiometry to calculate the ...
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0answers
15 views

Gas Equilibrium Constants

2SO2 + O2 -> 2SO3 V = 100l, temperature t = 25 celsius, P = 3atm. At first, put 8mol SO2 and 4mol O2. After balancing, P' = 2.2atm. Find Kc and Kp ? I try the formula PV = nRT. My solution is: ...
3
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1answer
80 views

Question on enol content

Arrange the following compounds in order of increasing enol content: I think it's $D>C>B>A$ considering conjugation, hyperconjugation and hydrogen bonding. The enol formed in case $D$ will ...
0
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1answer
46 views

What is the connection between vapor pressure and intermolecular force explanations of boiling?

I've had boiling explained to me in two ways, and I'm having trouble understanding how they connect. The first way is that a liquid is held together by the intermolecular forces, and boiling involves ...
2
votes
2answers
79 views

Equilibrium constant. Can it be reached?

Consider the reaction below: $$\ce{A + B <=> C}$$ Suppose that the equilibrium constant for this reaction is $K = 10$. I then prepare a reaction vessel with volume of $1~\mathrm{dm^{-3}}$ ...
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60 views

Calculating Solubility Product of AgCl from electrode potential

So I have to use a measured electrode potential to find the solubility product of AgCl. In our experiment, we first mixed one drop of 1.0M $\ce{AgNO3}$ with 10 mL of 1.0M $\ce{NaCl}$ to precipitate ...