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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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1answer
25 views

Which quantities change when choosing a different standard state?

Chemistry and biochemistry use a different standard state. For example, the standard hydrogen ion concentration is the one at pH = 0 in one case, and the one at neutral pH in the other case. Which ...
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2answers
125 views

Can I use the Henderson–Hasselbalch for calculating the pH of non-buffer systems?

Can I use the Henderson–Hasselbalch equation on reactions that are not buffers? When I read up on the derivation of the equation, I noticed that there is absolutely no assumption on the relative ...
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0answers
33 views

Derivation of relationship betwee standard Gibbs energy of reaction and equilibrium constant? [closed]

How does one derive $\Delta_\mathrm r G^\circ = -RT\ln(K)$? I don't see the connection mathematically or conceptually; how does Gibbs at all relate to the equilibrium constant of a reaction? This was ...
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0answers
30 views

Impact of pH? Change in Binding Affinity of protein-ligand complex based on pH and Kd?

When the $\mathrm{pH}$ was $5.0$, the temperature was $\pu{25 °C}$,the $K_\mathrm{D}$ was $\pu{5 μM}$, and [L] was equal to $K_D$, the protein(s) were half bound. Question considers half bound ...
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1answer
32 views

Chemical Equilibria - Fraction Bound equation based on Kd, [R], [L], [RL], is actually an average?

Let's say 150 stem cells express exactly 150 copies of the same mebrane antigen X. While all differentiated cells express exactly 15 copies of X. To the cell mixture you add a large amount of 0.2 μM ...
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2answers
45 views

Enzyme Kinetics - Given Km find substrate concentration at a certain velocity

From what I understand about the Michaelis Menten Model Km defines the amount of substrate required to reach half-saturation. 1/2 Vmax corresponds to Km on the x axis Generic formula is v = Kcat [...
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2answers
54 views

Thermodynamics - Series Reaction - Estimating mols of reactants based on Free Energy of Rxn

Question Three reactions occur simulteneously (assume ideal) at $\pu{T = 0^\circ C}$. $$\ce{A<=>B<=>C<=>D}$$ a) With $\Delta_r G^\circ_\text{AB} = \pu{400 J/mol}$, $\...
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1answer
457 views

When to use 1/Ka vs Kb [closed]

I'm really unsure what the difference is. We're using these when calculating $K$ of combined reactions. In general, I am also confused what $K$ is in comparison to $K_\mathrm{a}$ and $K_\mathrm{b}$. ...
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4answers
378 views

Colliding particles and activation energy

If two particles collide and they are under activation energy, why do they JUST “bounce apart”? Isn’t the activation energy steadily decreasing if those particles continuously collide? I always ...
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2answers
255 views

Find the pH of an amphiprotic salt dissolved in water at room temperature

Let's say I have a polyprotic acid $\ce{H2A}$ with the following properties: $$ \begin{align} \ce{H2A &<=> HA- + H+} & K_1 &= 1\cdot 10^{-1}\\ \ce{HA- &<=> A^2-+ H+} & ...
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1answer
1k views

pH of CH3COOH + HCl solution (shouldn't be a buffer)

$\pu{0.05 L}$ of a solution containing $\pu{0.3 M}$ acetic acid $(\ce{CH3COOH}$, $K_\mathrm{a} = \pu{1.8e-5})$ are added to $\pu{75 mL}$ of a solution containing $\pu{0.02 M}$ hydrochloric acid ($\ce{...
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0answers
31 views

Is position of equilibrium path independent?

I know that if a reaction is at equilibrium, then changes in condition may change the position of equilibrium and the direction is such shift can be predicted by Le Chatlier's rule. But now we're ...
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1answer
140 views

Can neutralization ever be complete?

Suppose we have 1 eq of acetic acid and we want neutralize it using sodium hydroxide. After adding 1 eq of sodium hydroxide 1 eq of sodium acetate should form and neutralization should be complete but ...
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0answers
59 views

Why is the reaction quotient Q always equal to one at standard state?

I understand that at equilibrium, $Q$ is equal to $K$. This should not depend how I express concentrations (as amount of substance concentrations $c$ or as partial pressures $p$ or as molality $b$ or ...
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2answers
98 views

Molarity Numerical on Water Gas Shift Reaction

For the water gas shift reaction below, $K_c = 3.491$ at a certain temperature. What are the equilibrium concentrations of all the components of the reaction if $\pu{0.3815 mol}$ of $\ce{CO}$ and $\ce{...
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1answer
96 views

How should we express concentrations and partial pressures in ΔG=-RTlnK? [duplicate]

I understand that $K$ will be dimensionless. Let's say an equilibrium involving $K_p$ and the reaction is $\ce{A -> B}$, $K_p$ will be dimensionless. If the reaction $\ce{A + B -> C}$, then ...
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4answers
51 views

What kind of system is required for dynamic equilibrium to be set up?

Most websites and books mention a closed system, but technically isn't an isolated system required? If energy can be transferred, then the position of of the equilibrium will continuously change and ...
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3answers
73 views

ICE table with changing volume without Kc [closed]

Just having trouble understanding how to approach an ICE table question with no Kc and a volume change Given If you had 4.4 mol of a solid, A, placed in a 1L container which decomposed in to B and ...
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1answer
115 views

Questions in Equilibrium [closed]

I have two inquiries concerning equilibrium: Does $K_c = 5.0$ indicate that the equilibrium mixture contains both products and reactants at an approximately equal amount? I know that $K_c \approx 1.0$...
2
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1answer
79 views

Proving a relation for fugacity of component i in term of independent variables (T,V)

In Molecular Thermodynamics of fluid phase equilibria by Prausnitz et al. [1] the authors recommend to use the following equation which gives the fugacity of component $i$ in terms of independent ...
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2answers
176 views

Statistical model of ligand substitution

Recently, I was told that in case of a particular step of a generic ligand substitution reaction: $$\ce{M(OH2)_{$N - n$}L_{n} + L <=> M(OH2)_{$N - n - 1$}L_{$n + 1$} + H2O}$$ The probability ...
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2answers
61 views

For Hess' law type questions, when do you take the inverse of the constant and when do you switch the sign?

For example, when you're given the enthalpy $\Delta H$ of a reaction and you want to switch that reaction around in order to add it to something else, you switch the sign. Furthermore, when adding ...
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0answers
41 views

Predicting Glycine-HCl's multiple equivalence points

I have currently completed a titration curve for glycine-HCl (2omL @ 0.1M, therefore 2.0mmol) where I have the known pH at each interval of added NaOH (adding 4mL each interval of 1.0M then measure pH)...
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1answer
110 views

Equilibrium Constants For Phenol Tautomers

I encountered the following equilibrium constant values for the keto-enol interconversions of phenol in Organic Chemistry (Solomons, Fryhle, Snyder, 3rd Edition): I wonder what could explain the ...
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1answer
71 views

Equilibrium constant of water

If $\ce{H2O}$ dissociates as follows: $$\ce{2H2O <=> H3O+ + OH-}$$ and not in this way: $$\ce{H2O <=> H+ + OH-}$$ why is the equilibrium constant: $$K_{eq}=\frac {\ce{[H+][OH-]}} {\ce{[H2O]...
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0answers
61 views

Stoichiometry based on addition of simultaneous equilibria

I read on another equilibrium question that if two equilibria occur at the same time, then it is not accurate with actual stoichiometry to add the two equations and multiply the equilibrium constants $...
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0answers
42 views

Derivation of equilibrium constant [duplicate]

In general chemistry, we learn that the equilibrium constant, defined in terms of activities, for the reaction $$\ce{aA + bB -> cD + dD}$$ is given by $$K_\mathrm{eq} = \frac{(\ce{C})^c(\ce{D})^...
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1answer
815 views

Calculate pH at equivalence point [closed]

Calculate the pH at the equivalence point of a titration of 62 mL of 0.1 M $\ce{CH_3NH_2}$ with 0.20 M HCl. The $\ce{K_b}=4.4\cdot10^{-4}$. At the equivalence point, the moles of CH3NH2 equals the ...
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2answers
186 views

Derivation of Gibbs free energy formula

Okay, so I'm trying to derive an important formula which states that - ∆G(r) = ∆G° + RTln( RQ ) where ∆G(r) is the instantaneous rate of change of Gibbs energy with ...
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0answers
36 views

Why is high pressure and high temperature favourable for the formation of diamond? [duplicate]

Graphite can be converted to diamond and this conversion is favourable under high pressure and high temperature. Is there a reason for this from the point of view of "Le Chatelier's Principle"? I ...
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0answers
32 views

What is the reasoning behind deriving electrode potential of a metal-metal sparingly soluble salt electrode?

Considering a sparingly soluble salt $M_xN_y$ of the metal $M$, in which the corresponding reaction is $M_xN_y$ = $xM^{y+}$ + $yN^{x-}$, the standard electrode potential is given by $E^{o}_{M_xN_y/M/...
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1answer
59 views

Effect of inert gas on Q

Adding an inert gas will not affect Q if that reaction is held at a constant volume. But, if the reaction is held at constant pressure, then adding inert gas will change Q bc the partial pressures of ...
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2answers
102 views

Who developed the concept of ICE tables?

Many general chemistry courses (at least in the US) or online tutorials solve problems of chemical equilibrium by using ICE (sometimes RICE) tables, which track how the moles of reactants and products ...
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2answers
124 views

Determining Kc for the equilibrium involving iron thiocyanate using spectrophotometric data

$$\ce{Fe^3+(aq) + SCN-(aq) <=> [Fe(SCN)]^2+(aq)}$$ $\pu{12.0 mL}$ of $\pu{0.00110 mol L-1}$ $\ce{Fe^3+}$ was added to $\pu{6.00 mL}$ of $\pu{0.00140 mol L-1}$ $\ce{SCN-}$. The absorbance of ...
3
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3answers
316 views

Which acid/base does a strong base/acid react when added to a buffer solution?

I'm in high school chemistry and just learning about buffer solutions. For example, given a buffered solution of $\ce{CH3COOH}$ and $\ce{NaCH3COO}$ with $K_a = 1.8 \times 10^{-5}$, we might want to ...
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0answers
27 views

Regarding ΔG and equilibrium constant [duplicate]

We know that $$ΔG = ΔG^\circ + RT\ln{Q} \tag{1}$$ where $Q$ is reaction quotient, and also that at equilibrium becomes $$ΔG^\circ = -RT\ln{k} \tag{2}$$ I was trying to apply this equation to a ...
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2answers
148 views

Calculating the pH of a buffer made by a diprotic acid and its double salt

The concentration of the diprotic acid (tartaric acid) will be constant at $\pu{ 0.1 M}$. I want to find the concentration of its double salt (potassium sodium tartrate) needed to create a buffer of $\...
2
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2answers
88 views

Please explain the mystery of the equilibrium constant expression for chemical reactions [closed]

Given a reversible chemical reaction, e.g. $$\ce{CuCl4^2-(aq) <=> Cu^2+(aq) + 4Cl-(aq) + \text{heat}}$$ occurring in a medium, the equilibrium constant is defined as $$K = \frac{[\ce{Cu^2+}][\ce{...
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0answers
39 views

Equilibrium Constant and Reaction Mechanism [duplicate]

How is it possible for the equilibrium constant to not depend on a reaction's mechanism? For the elementary reaction $$aA + bB \rightleftharpoons dD + eE$$ I understand that the rate of the ...
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2answers
370 views

Equilibrium constant for esterification process

Teacher told us that the concentration term for pure liquids and solids is always $1$. But online I found this reaction: $$\ce{CH3COOH(l) + CH3CH2OH(l) <=> CH3COOCH2CH3(l) + H2O(l)}$$ ...
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1answer
171 views

How to calculate the equilibrium constant for nitrogen, hydrogen, and ammonia?

$\pu{2 mol}$ of $\ce{N2}$ is mixed with $\pu{6 mol}$ of $\ce{H2}$ in a closed vessel of $\pu{1 L}$ capacity. If $50\%$ of $\ce{N2}$ is converted into $\ce{NH3}$ at equilibrium, what is the value of $...
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1answer
29 views

Should I include ions from the solvent in solubility product constant calculations?

I'm trying to determine the Solubility Constant $K_\mathrm{sp}$ of $\ce{Ba(NO3)2}$ dissolved in nitric acid solution $\ce{HNO3}$ from experimental data. $\ce{HNO3}$ will be mostly dissociated so ...
3
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1answer
137 views

Is a discharged battery in a state of chemical equilibrium?

A reaction that has reached chemical equilibrium no longer shows changes in reactant and product concentrations, but forward and reverse reactions are still going on. I'm confused whether a completely ...
2
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1answer
500 views

What is the concentration of H2 for the equation H2+I2=2HI if the equilibrium constant is 64 and the initial concentrations are both 1.9

So for this, I set up the equation = $$64= \frac{(x)^2}{(1.9-x)^2}$$ I took the sqrt of both sides and got $$8=\frac{x}{(1.9-x)}$$ So then I did $$8(1.9-x)=x$$ And simplified I got $$15.2=9x$$ ...
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0answers
14 views

How to describe the ionization equilibria of multiple ionizable species

For a weak acid [PB] in a buffered solution [H2PO4]/[HPO4] at pH 7.5 where: If some of the species [PB] was removed from the solution by partitioning on to an adsorbent, the equilibrium of [PB] ...
2
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2answers
372 views

Gibbs free energy in standard state vs. equilibrium

I have a problem with the definition of the standard Gibbs energy and its connection to the equilibrium constants. I think, that I've basically understood what the different equation mean but there ...
1
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0answers
205 views

Conversion of graphite into diamond [duplicate]

The standard state Gibbs free energies of formation of C(graphite) and C(diamond) at $T = \pu{298 K}$ are $\pu{0 kJ mol-1}$ and $\pu{2.9 kJ mol-1}$, respectively. The conversion of graphite [C(...
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2answers
152 views

Why neglecting OH Ions from charge balance?

I have a problem, in which the concentration of $\ce{Ca^{2+}}$ ions in water should be related to the partial pressure of $\ce{CO2}$ (assuming the water is an open system and in equilibrium with ...
1
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2answers
85 views

Ionic equilibrium between multiple ions

This is a question from IIT-JEE 1993: For the reaction $$\ce{[Ag(CN)2]^- -> Ag^+ + 2CN^-}$$ the equilibrium constant at $\pu{298 K}$ is $\pu{4e-10}$. The silver ion concentration in a ...
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1answer
64 views

Drug pH and pKa known, is it an acid or a base? [closed]

I want to answer the question if a drug which is analysed for pH and pKa is ionised or not ionised in a cow stomach with a pH of 6. The drug has a pH of 8,52 and a pKa of 8,78. Since the pH is 8,52 ...