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Questions and Answers
Which statement accurately describes dynamic equilibrium?
Which statement accurately describes dynamic equilibrium?
- The concentrations of reactants and products are equal.
- The rate of the forward reaction is faster than the rate of the reverse reaction.
- The concentrations of reactants and products no longer change because the forward and reverse reactions continue at the same rate. (correct)
- All reactions have ceased as equilibrium is achieved.
Consider the following reaction at equilibrium: $aA + bB \rightleftharpoons cC + dD$. Which expression correctly represents the equilibrium constant, $K_c$?
Consider the following reaction at equilibrium: $aA + bB \rightleftharpoons cC + dD$. Which expression correctly represents the equilibrium constant, $K_c$?
- $K_c = \frac{[aA]^a[bB]^b}{[cC]^c[dD]^d}$
- $K_c = \frac{[A]^a[B]^b}{[C]^c[D]^d}$
- $K_c = \frac{[C]^c[D]^d}{[A]^a[B]^b}$ (correct)
- $K_c = \frac{[cC]^c[dD]^d}{[aA]^a[bB]^b}$
What is a characteristic feature of heterogeneous equilibria?
What is a characteristic feature of heterogeneous equilibria?
- The reaction proceeds rapidly to completion.
- Reactants and products exist in multiple phases. (correct)
- All reactants and products are in the gaseous phase.
- All reactants and products are in the same phase.
The equilibrium constant, $K_c$, for a reaction is very large. What does this indicate about the equilibrium position?
The equilibrium constant, $K_c$, for a reaction is very large. What does this indicate about the equilibrium position?
Consider the gas-phase reaction: $N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)$. Initially, a reaction vessel contains 2.0 mol of $N_2$ and 6.0 mol of $H_2$. At equilibrium, the amount of $NH_3$ formed is 2.0 mol. What is the amount of $N_2$ remaining at equilibrium?
Consider the gas-phase reaction: $N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)$. Initially, a reaction vessel contains 2.0 mol of $N_2$ and 6.0 mol of $H_2$. At equilibrium, the amount of $NH_3$ formed is 2.0 mol. What is the amount of $N_2$ remaining at equilibrium?
What does Le Chatelier's principle state?
What does Le Chatelier's principle state?
For the reaction $N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)$, what effect would increasing the pressure have on the equilibrium?
For the reaction $N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)$, what effect would increasing the pressure have on the equilibrium?
How does the change in Gibbs free energy, $\Delta G$, relate to the equilibrium constant, $K$?
How does the change in Gibbs free energy, $\Delta G$, relate to the equilibrium constant, $K$?
Consider the reaction $A(g) + B(g) \rightleftharpoons C(g)$. At a certain temperature, the equilibrium concentrations are $[A] = 2M$, $[B] = 3M$, and $[C] = 4M$. What is the value of the equilibrium constant $K_c$?
Consider the reaction $A(g) + B(g) \rightleftharpoons C(g)$. At a certain temperature, the equilibrium concentrations are $[A] = 2M$, $[B] = 3M$, and $[C] = 4M$. What is the value of the equilibrium constant $K_c$?
For an endothermic reaction, how does increasing the temperature affect the equilibrium constant $K$?
For an endothermic reaction, how does increasing the temperature affect the equilibrium constant $K$?
Which of the following will NOT cause a change in the equilibrium position for the reaction $H_2(g) + I_2(g) \rightleftharpoons 2HI(g)$?
Which of the following will NOT cause a change in the equilibrium position for the reaction $H_2(g) + I_2(g) \rightleftharpoons 2HI(g)$?
What is the SI unit for the standard state concentration used in defining equilibrium constants for solutions?
What is the SI unit for the standard state concentration used in defining equilibrium constants for solutions?
Consider the reaction: $2SO_2(g) + O_2(g) \rightleftharpoons 2SO_3(g)$. If the volume of the container is decreased, what will happen to the equilibrium?
Consider the reaction: $2SO_2(g) + O_2(g) \rightleftharpoons 2SO_3(g)$. If the volume of the container is decreased, what will happen to the equilibrium?
For the equilibrium $A(s) \rightleftharpoons B(g)$, which expression is correct for $K_c$?
For the equilibrium $A(s) \rightleftharpoons B(g)$, which expression is correct for $K_c$?
How is the reaction quotient, $Q$, different from the equilibrium constant, $K$?
How is the reaction quotient, $Q$, different from the equilibrium constant, $K$?
If $Q < K$ for a reaction, what does this indicate about the direction the reaction will proceed?
If $Q < K$ for a reaction, what does this indicate about the direction the reaction will proceed?
A reaction has an equilibrium constant $K = 100$. Initially, $[A] = 2M$ and $[B] = 1M$, and the reaction is $A \rightleftharpoons B$. Calculate $Q$ and determine which way the reaction will shift.
A reaction has an equilibrium constant $K = 100$. Initially, $[A] = 2M$ and $[B] = 1M$, and the reaction is $A \rightleftharpoons B$. Calculate $Q$ and determine which way the reaction will shift.
The reaction $N_2O_4(g) \rightleftharpoons 2NO_2(g)$ is endothermic. If the temperature is increased, which way will the equilibrium shift?
The reaction $N_2O_4(g) \rightleftharpoons 2NO_2(g)$ is endothermic. If the temperature is increased, which way will the equilibrium shift?
For the exothermic reaction $2SO_2(g) + O_2(g) \rightleftharpoons 2SO_3(g)$, what happens to $K$ if the temperature is increased?
For the exothermic reaction $2SO_2(g) + O_2(g) \rightleftharpoons 2SO_3(g)$, what happens to $K$ if the temperature is increased?
Consider $PCl_5(g) \rightleftharpoons PCl_3(g) + Cl_2(g)$. What happens if $Cl_2$ is added to the system at equilibrium?
Consider $PCl_5(g) \rightleftharpoons PCl_3(g) + Cl_2(g)$. What happens if $Cl_2$ is added to the system at equilibrium?
Which change will increase the number of moles of $SO_3$ at equilibrium in the following reaction: $2SO_2(g) + O_2(g) \rightleftharpoons 2SO_3(g)$ $\Delta H = -197 kJ/mol$?
Which change will increase the number of moles of $SO_3$ at equilibrium in the following reaction: $2SO_2(g) + O_2(g) \rightleftharpoons 2SO_3(g)$ $\Delta H = -197 kJ/mol$?
Given the reaction $CO(g) + Cl_2(g) \rightleftharpoons COCl_2(g)$ with $K = 4.56 \times 10^0$ at $100^\circ C$, what does this $K$ value indicate about the reaction at equilibrium?
Given the reaction $CO(g) + Cl_2(g) \rightleftharpoons COCl_2(g)$ with $K = 4.56 \times 10^0$ at $100^\circ C$, what does this $K$ value indicate about the reaction at equilibrium?
How does standard reaction Gibbs free energy relate to spontaneity of a reaction?
How does standard reaction Gibbs free energy relate to spontaneity of a reaction?
For the dissolution of an ionic compound in water, what is the effect of temperature if the process is endothermic?
For the dissolution of an ionic compound in water, what is the effect of temperature if the process is endothermic?
What conditions favor the formation of products in the reaction: $A(g) + B(g) \rightleftharpoons C(g) + heat$?
What conditions favor the formation of products in the reaction: $A(g) + B(g) \rightleftharpoons C(g) + heat$?
Consider the equilibrium: $2NOBr(g) \rightleftharpoons 2NO(g) + Br_2(g)$. What is the correct expression for $K_c$?
Consider the equilibrium: $2NOBr(g) \rightleftharpoons 2NO(g) + Br_2(g)$. What is the correct expression for $K_c$?
Which of the following is true regarding the addition of an inert gas to a system at equilibrium, assuming constant volume?
Which of the following is true regarding the addition of an inert gas to a system at equilibrium, assuming constant volume?
What does a small value of the dissociation constant ($K_d$) in protein-ligand binding indicate?
What does a small value of the dissociation constant ($K_d$) in protein-ligand binding indicate?
What should be the primary consideration when determining the effect of pressure on an equilibrium system involving gases?
What should be the primary consideration when determining the effect of pressure on an equilibrium system involving gases?
Consider the reaction: $A(g) + B(s) \rightleftharpoons C(g)$. If the partial pressure of $A$ is increased, which way will the equilibrium shift?
Consider the reaction: $A(g) + B(s) \rightleftharpoons C(g)$. If the partial pressure of $A$ is increased, which way will the equilibrium shift?
For a certain reaction, $\Delta H = -50 kJ/mol$ and $\Delta S = -100 J/(mol \cdot K)$ at 298 K. Is the reaction spontaneous at this temperature?
For a certain reaction, $\Delta H = -50 kJ/mol$ and $\Delta S = -100 J/(mol \cdot K)$ at 298 K. Is the reaction spontaneous at this temperature?
What is the standard state pressure for gases when defining equilibrium constants?
What is the standard state pressure for gases when defining equilibrium constants?
In the protein-ligand binding context, if the reaction lies to the left, what does that indicate about the reaction?
In the protein-ligand binding context, if the reaction lies to the left, what does that indicate about the reaction?
Consider the reaction $A(g) + B(g) \rightleftharpoons C(g)$. Initially, only A and B are present. At equilibrium, it is found that the concentration of C is much lower than A or B. What can be inferred about the equilibrium constant, $K$?
Consider the reaction $A(g) + B(g) \rightleftharpoons C(g)$. Initially, only A and B are present. At equilibrium, it is found that the concentration of C is much lower than A or B. What can be inferred about the equilibrium constant, $K$?
Why does increasing the temperature generally increase the rate of a chemical reaction, even if the reaction is not at equilibrium?
Why does increasing the temperature generally increase the rate of a chemical reaction, even if the reaction is not at equilibrium?
For a system at equilibrium, what is the effect of adding a catalyst?
For a system at equilibrium, what is the effect of adding a catalyst?
Given the endothermic reaction $A(g) \rightleftharpoons B(g)$. How would the concentration of B change if more A is introduced into the system after it has reached equlibirum?
Given the endothermic reaction $A(g) \rightleftharpoons B(g)$. How would the concentration of B change if more A is introduced into the system after it has reached equlibirum?
Flashcards
Dynamic Equilibrium
Dynamic Equilibrium
A state where the rates of forward and reverse reactions are equal, and concentrations of reactants/products remain constant.
Heterogeneous Equilibria
Heterogeneous Equilibria
A state where reactants and products coexist, but are in different phases.
Position of Equilibrium
Position of Equilibrium
The value of the equilibrium constant determines whether products or reactants are favored.
Le Chatelier's Principle
Le Chatelier's Principle
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Reaction Completion
Reaction Completion
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Equilibrium Reaction
Equilibrium Reaction
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Concentrations at Equilibrium
Concentrations at Equilibrium
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Equilibrium Constant (K)
Equilibrium Constant (K)
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Reaction Quotient (Q)
Reaction Quotient (Q)
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Q = K
Q = K
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Q > K
Q > K
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Q < K
Q < K
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Increase in Pressure
Increase in Pressure
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Decrease in Pressure
Decrease in Pressure
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Exothermic Reaction and Temperature
Exothermic Reaction and Temperature
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Endothermic Reaction and Temperature
Endothermic Reaction and Temperature
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Free Energy and Equilibrium
Free Energy and Equilibrium
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Study Notes
Dynamic Equilibrium
- Chemical reactions do not always go to completion
- Equilibrium reactions proceed in forward and backward reaction
Approaching Equilibrium
- As time progresses, the rate of the forward reaction changes less quickly
- A + B is consumed by forward reaction and formed by back reaction
- As time progresses, the rate of the back reaction changes less quickly
- C + D is formed by forward reaction and consumed by back reaction
- If equilibrium is established there is no further visible change in the reaction
- Forward and reverse reactions continue at the same rate when equilibrium is established
- Reactants and products reach a steady state in dynamic equilibrium
- Reactant and product concentrations are not necessarily equal
Equilibrium Constant
- Equilibrium constant (K) for the reaction αA + βB ⇌ γC + δD
- K is ([C]^γ [D]^δ) / ([A]^α [B]^β)
- For the reaction A + 2B ⇌ 3C+D, K is [C]³[D] / ([A][B]²)
- Pure solids and liquids aren't included in the equilibrium constant
- For solutions, the standard state concentration is 1 mol dm⁻³
- For gases, the standard state pressure is 1 bar
- Equilibrium constant has no units
- The value of K is fixed once equilibrium as been established
Reaction Quotient
- Reaction quotient (Q) for the reaction αX + βY ⇌ γZ
- Q is the ratio of products to reactants, at any stage of the reaction
- Q = K: No shift will occur with the system at equilibrium
- Q > K: Ratio of products to reactants is too large
- A net change of products to reactants must occur in order to reach equilibrium
- System shifts to the left, consuming products and forming reactants, until equilibrum is achieved
- Q < K: Ratio of products to reactants is too small
- A net change of reactants to products must occur in order to reach equilibrium
- System shifts to the right, consuming reactants and forming products, until equilibrium is achieved
- For the reaction SO₂(g) + NO₂(g) ⇌ SO₃(g) + NO(g) with K = 3.75, if all four gases had initial concentrations of 0.8000 mol dm⁻³, Q = 1
Le Chatelier's Principle
- The concentration of reactants and products in an equilibrium mixture will alter so as to counteract any changes in pressure, temperature and concentration
- Add reactant: Forward reaction to remove stress
- Remove reactant: Reverse reaction to remove stress
- Add product: Reverse reaction to remove stress
- Remove product: Forward reaction to remove stress
- Decrease volume: Shifts toward fewer moles in the gas phase to remove stress
- Increase volume: Shifts toward more moles in the gas phase to remove stress
- Raise temperature of endothermic reaction: Forward, new value for K to remove stress
- Lower temperature of endothermic reaction: Reverse, new value for K to remove stress
- Raise temperature of exothermic reaction: Reverse, new value for K to remove stress
- Lower temperature of exothermic reaction: Forward, new value for K to remove stress
- Catalyst: No effect to remove stress
Pressure Changes
- Pressure of a reaction system involving gaseous components can be altered by
- Adding or removing a gaseous reactant or product
- Adding an inert gas (one not involved in the reaction)
- Changing the container volume
Volume Changes
- If pressure increases as a result of the volume decreasing, the system responds by decreasing the pressure, by reducing the number of gas phase molecules
- If pressure decreases as a result of the volume increasing, the system responds by increasing the pressure, by increasing the number of gas phase molecules
- For reaction PCl3(g) + 3 NH3(g) ⇌ P(NH2)3(g) + 3 HCl(g), there is no shift
Free Energy and Equilibrium
- ΔᵣG° = -RT ln K
- ΔᵣG° being standard reaction Gibbs free energy
- R being the gas constant = 8.314 J K⁻¹ mol⁻¹
- T being absolute temperature in K
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Description
Explore dynamic equilibrium in chemical reactions, where forward and backward reactions occur simultaneously. Understand how reactants and products reach a steady state, with concentrations that aren't necessarily equal. Learn about the equilibrium constant (K) and its calculation for various reactions.
