16. Chemical Equilibrium

Le Chatelier's Principle

15.2 Le Chatelier's Principle | General Chemistry

In automobile catalytic converters, the air pollutant nitric oxide is converted to nitrogen and oxygen. Listed in the table are forward and reverse rate constants for the reac- tion 2 NO1g2 ∆ N21g2 + O21g2. Temperature (K) kf1M — 1 s-12 kr1M-1 s — 12
1400 0.29 1.1 * 10-6
1500 1.3 1.4 * 10-5
Is the reaction endothermic or exothermic? Explain in terms of kinetics.

When 2.00 mol of SO2Cl2 is placed in a 2.00-L flask at 303
K, 56% of the SO2Cl2 decomposes to SO2 and Cl2 :
SO2Cl21g2 Δ SO21g2 + Cl21g2
(c) According to Le Châtelier’s principle, would the percent of SO2Cl2
that decomposes increase, decrease or stay the same if the
mixture were transferred to a 15.00-L vessel?

When lead(IV) oxide is heated above 300 C, it decomposes
according to the following reaction PbO21s2Δ
PbO1s2 + O21g2. Consider the two sealed vessels of PbO2
shown here. If both vessels are heated to 400 C and
allowed to come to equilibrium, which of the following
statements is true? (a) There will be less PbO2 remaining
in vessel A [Section 15.4]

Consider the following equilibrium for which H 6 0
2 SO21g2 + O21g2 Δ 2 SO31g2
How will each of the following changes affect an equilibrium
mixture of the three gases: (f) SO31g2 is removed
from the system?

The enthalpy change, ΔH, is equal to zero.

The following data was collected for the following reaction at equilibrium&nbsp;2 A (g) + 3 B (g) &nbsp;⇌ C (g) &nbsp; &nbsp;&nbsp;At 25 oC K is 5.2 x 10-4 and at 50&nbsp;oC K is 1.7 x 10-7. Which of the following statements is true?a) The reaction is exothermic.b) The reaction is endothermic.c) The enthalpy change, ΔH, is equal to zero.d) Not enough information is given.&nbsp;

When lead(IV) oxide is heated above 300 C, it decomposes
according to the following reaction PbO21s2Δ
PbO1s2 + O21g2. Consider the two sealed vessels of PbO2
shown here. If both vessels are heated to 400 C and
allowed to come to equilibrium, which of the following
statements is true? (b) There will be less PbO2 remaining in vessel
B. [Section 15.4]
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/2d9fb7a9b719bdc5-1666363936031.jpg" alt="" />

The binding of oxygen by hemoglobin in the blood involves the
equilibrium reaction:
HbH+(aq) + O2(aq)HbO2(aq) + H+(aq)
In this equation, Hb is hemoglobin. The pH of normal human
blood is highly controlled within a range of 7.35 to 7.45. Given the
above equilibrium, why is this important? What would happen to
the oxygen-carrying capacity of hemoglobin if blood became too
acidic (a dangerous condition known as acidosis)?

Consider the exothermic reaction
CoCl 2-1aq2 + 6 H O1l2 ∆ Co1H O2 2 + 1aq2 + 4 Cl-1aq2 which interconverts the blue CoCl 2- ion and the pink
Co 2 +CoCl 2- increase or decrease when the following changes occur?(c) The solution is diluted with water.

According to Le Chatelier&rsquo;s Principle if a system (chemical reaction) is at equilibrium and we disturb it then the system will readjust to maintain it&rsquo;s equilibrium state.

Consider the reaction
4 NH31g2 + 5 O21g2 Δ
4 NO1g2 + 6 H2O1g2, H = -904.4 kJ
Does each of the following increase, decrease, or leave
unchanged the yield of NO at equilibrium? 
(e) add a catalyst

The following reaction is important in gold mining: 4 Au1s2 + 8 CN-1aq2 + O21g2 + 2 H2O1l2 ∆ 4 Au1CN22-1aq2 + 4 OH-1aq2For a reaction mixture at equilibrium, in which direction would the reaction go to reestablish equilibrium after each of the following changes?
(a) Adding gold

Thermodynamics and Le Chatelier’s Principle

Consider this reaction at equilibrium:
2 BrNO(g) ⇌ 2 NO(g) + Br2(g)
Predict whether the reaction will shift left, shift right, or remain unchanged after each disturbance.
b. BrNO is added to the reaction mixture.

Each reaction is allowed to come to equilibrium, and then the
volume is changed as indicated. Predict the effect (shift right, shift left, or no effect) of the indicated volume change.
b. 2 H2S( g) ⇌ 2 H2( g) + S2( g) (volume is decreased)

Correct, Q is greater than K.

 Compare the reaction quotient to the equilibrium constant to determine which way the reaction will shift. 

In which direction will the following reaction proceed when PCO = 0.13 atm, PH2O = 0.56 atm, PCO2 = 0.62 atm, and PH2 = 0.43 atm. Kp for the reaction is 2.7. CO (g) + H2O (g) &#8646; CO2 (g) + H2 (g)

At a temperature of 700 K, the forward and reverse rate
constants for the reaction 2 HI1g2 ΔH21g2 + I21g2
are kf = 1.8 * 10-3 M-1 s-1 and kr = 0.063 M-1 s-1.
(b) Is the forward reaction endothermic or exothermic
if the rate constants for the same reaction have
values of kf = 0.097 M-1 s-1 and kr = 2.6 M-1 s-1 at 800 K?

At 1000 K, Kp = 2.1 * 106 and ΔH° = - 107.7 kJ for the reaction H21g2 + Br21g2 ∆ 2 HBr1g2.
(b) For the equilibrium in part (a), each of the following changes will increase the equilibrium partial pressure of HBr. Choose the change that will cause the greatest increase in the pressure of HBr, and explain your choice.
(ii) Adding 0.10 mol of Br2

LeChatelier: Change in Temperature

Consider this reaction at equilibrium:
C(s) + H2O(g) ⇌ CO(g) + H2(g)
Predict whether the reaction will shift left, shift right, or remain unchanged after each disturbance.
a. C is added to the reaction mixture.

Consider the reaction
4 NH31g2 + 5 O21g2 Δ
4 NO1g2 + 6 H2O1g2, H = -904.4 kJ
Does each of the following increase, decrease, or leave
unchanged the yield of NO at equilibrium?
(f) increase temperature.

While the reaction does shift to the left, the concentration of the product will not be this low.  The calculation of the concentration of the product must take into consideration the direction in which the equilibrium will shift as well as the initial concentration of the product.

The concentration of the product at equilibrium is needed. This value is that of the reactants at equilibrium.

The stoichiometry of the reaction must be considered in the calculation.

Correct, the reaction will shift toward the left decreasing the concentration of the product.

The reaction will shift to the left decreasing the amount of product when equilibrium is attained.

Be sure to check the magnitudes of Q and K to determine in which direction the reaction will shift.

At 445 &#186;C calculate the equilibrium concentration of HI when 0.500 M HI, 0.0200 M H2, and 0.0200 M I2 are placed in a sealed flask and allowed to reach equilibrium. Kc for this reaction is 50 at 445 &#186;C. H2 (g) + I2 (g) &#8646; 2 HI (g)

Le Châtelier’s Principle

An Equilibrium View of Le Chatelier's Principle

The value of Kw increases with increasing temperature. Is the 
autoionization of water endothermic or exothermic?

The water–gas shift reaction CO1g2 + H2O1g2Δ
CO21g2 + H21g2 is used industrially to produce hydrogen.
The reaction enthalpy is H = -41 kJ.
(b) Could you increase the equilibrium yield
of hydrogen by controlling the pressure of this reaction? If
so would high or low pressure favor formation of H2(g)?

The following picture represents the composition of the equi- librium mixture for the endothermic reaction A2 ∆ 2 A at 500 K. Draw a picture that represents the equilibrium mixture after each of the following changes.
(c) Decreasing the temperature<img src="https://lightcat-files.s3.amazonaws.com/problem_images/6b98079c2a3abad4-1672465021974.jpg" alt="" />

Given the Arrhenius equation, k = Ae-Ea>RT, and the rela- 
tion between the equilibrium constant and the forward and 
reverse rate constants, Kc = kf>kr, explain why Kc for an exothermic reaction decreases with increasing temperature.

Each reaction is allowed to come to equilibrium, and then the volume is changed as indicated. Predict the effect (shift right, shift left, or no effect) of the indicated volume change.
a. CO( g) + H2O( g) ⇌ CO2( g) + H2( g) (volume is decreased)

The valuable polymer polyurethane is made by a condensa- tion reaction of alcohols (ROH) with compounds that con- tain an isocyanate group (RNCO). Two reactions that can generate a urethane monomer are shown here: (i) <img src="https://lightcat-files.s3.amazonaws.com/problem_images/ef292396b764c618-1666360422730.jpg" alt="" /> (ii) <img src="" alt="" /> (c) If you wanted to promote the formation of the isocya- nate intermediate in each reaction, what could you do, using Le Châtelier’s principle?

The addition of an inert gas does not change the concentration nor the partial pressure of either I or I2 and therefore does not disturb the equilibrium.

The partial pressure of I2 will increase.

No change; the reaction is at equilibrium.

Correct, the inert gas does not change the concentration or partial pressure of any of the species in the reaction.

 Le Ch&#226;telier&#8217;s Principle states that when a system at equilibrium is disturbed, the system shifts in a direction that minimizes the disturbance. 

A container is charged with 2.00 mol of I2 and is allowed to reach equilibrium. The I2 decomposes to iodine atoms as shown in the following reaction: I2 (g) &#8646; 2 I (g) After the reaction reaches equilibrium, an inert gas is introduced into the container under conditions of constant volume. Which of the following would you expect to happen?

The following pictures represent the composition of the equi- librium mixture for the reaction A + B ∆ AB at 300 K and at 400 K. <img src="https://lightcat-files.s3.amazonaws.com/problem_images/8f944ba4a663f37b-1672458645600.jpg" alt="" /> Is the reaction exothermic or endothermic? Explain using Le Châtelier’s principle.

Methanol 1CH3OH2 can be made by the reaction of CO
with H2:
CO1g2 + 2 H21g2 Δ CH3OH1g2
(b) To maximize the equilibrium
yield of methanol, would you use a high or low temperature?

Equilibrium: Crash Course Chemistry #28

Thermodynamics

Carbon dioxide dissolves in water according to the equations:
CO2( g) + H2O(l )H2CO3(aq)
H2CO3(aq) + H2O(l)HCO3-(aq) + H3O+(aq)
Carbon dioxide levels in the atmosphere have increased about
20% over the last century. Given that Earth’s oceans are exposed
to atmospheric carbon dioxide, what effect might the increased
CO2 be having on the pH of the world’s oceans? What effect
might this change be having on the limestone structures (primarily
CaCO3) of coral reefs and marine shells?

Consider the hypothetical reaction A1g2 Δ 2 B1g2. A
flask is charged with 0.75 atm of pure A, after which it is
allowed to reach equilibrium at 0 C. At equilibrium, the
partial pressure of A is 0.36 atm.
(c) What could we do to maximize the yield of B?

Consider the reaction A + B ∆ AB. The vessel on the right contains an equilibrium mixture of A molecules (red spheres), B molecules (blue spheres), and AB molecules. If the stopcock is opened and the contents of the two vessels are allowed to mix, will the reaction go in the forward or reverse direction? Explain. <img src="https://lightcat-files.s3.amazonaws.com/problem_images/e5d3cc2b2dbcf28d-1672527288655.jpg" alt="" />

The equilibrium constant Kp for the reaction PCl51g2 ∆ PCl31g2 + Cl21g2 is 3.81 * 102 at 600 K and 2.69 * 103 at 700 K.
(b) How are the equilibrium amounts of reactants and products affected by (iii) addition of a catalyst?

Consider the reaction below:CH4 (g) &nbsp;+ &nbsp;F2 (g) &nbsp;⇌ &nbsp;CF4 (g) &nbsp;+ HF (g) &nbsp; H = + 38.1 KJ/molThe following changes will shift the equilibrium to the left except one. Which one would not cause a shift to the left?

(b) If the temperature is raised by 100 K, does
the equilibrium constant for this reaction increase or decrease?

A<img src="https://static.studychannel.pearsonprd.tech/courses/general-chemistry/thumbnails/images/ecfc52ec"alt=""/>

B<img src="https://static.studychannel.pearsonprd.tech/courses/general-chemistry/thumbnails/images/c330bea1"alt=""/>

Consider the following gas reaction of A2 ( shaded spheres) and B2 ( unshaded spheres)A2 (g) &nbsp;+ &nbsp;B2&nbsp;(g) &nbsp;⇌ &nbsp;2 AB (g)&nbsp;Which container proceeds more to completion?&nbsp;

Coal, which is primarily carbon, can be converted to natural gas, primarily CH4, by the exothermic reaction:
C(s) + 2 H2(g) ⇌ CH4(g) Which disturbance will favor CH4 at equilibrium? 
b. adding more H2 to the reaction mixture

The following is an endothermic reaction where Kc = 6.73 x 103.For each of the choices below predict in which direction the reaction will proceed

Consider the reaction
4 NH31g2 + 5 O21g2 Δ
4 NO1g2 + 6 H2O1g2, H = -904.4 kJ
Does each of the following increase, decrease, or leave
unchanged the yield of NO at equilibrium? 
(d) decrease
the volume of the container in which the reaction occurs

Consider this reaction at equilibrium:
2 BrNO(g) ⇌ 2 NO(g) + Br2(g)
Predict whether the reaction will shift left, shift right, or remain unchanged after each disturbance.
a. NO is added to the reaction mixture.

Consider this reaction at equilibrium:
2 BrNO(g) ⇌ 2 NO(g) + Br2(g)
Predict whether the reaction will shift left, shift right, or remain unchanged after each disturbance.
c. Br2 is removed from the reaction mixture.

Consider the endothermic reaction: C2H4(g) + I2(g) ⇌ C2H4I2(g)
If you were trying to maximize the amount of C H I produced, 242
which tactic might you try? Assume that the reaction mixture reaches equilibrium.
a. decreasing the reaction volume
b. removing I2 from the reaction mixture
c. raising the reaction temperature
d. adding C2H4 to the reaction mixture

When lead(IV) oxide is heated above 300 C, it decomposes
according to the following reaction PbO21s2Δ
PbO1s2 + O21g2. Consider the two sealed vessels of PbO2
shown here. If both vessels are heated to 400 C and
allowed to come to equilibrium, which of the following
statements is true? (c) The amount of PbO2 remaining in each vessel will
be the same. [Section 15.4]

Ozone, O3, decomposes to molecular oxygen in the stratosphere 
according to the reaction 2 O31g2¡3 O21g2. 
Would an increase in pressure favor the formation of 
ozone or of oxygen?

Consider the reaction
4 NH31g2 + 5 O21g2 Δ
4 NO1g2 + 6 H2O1g2, H = -904.4 kJ
Does each of the following increase, decrease, or leave
unchanged the yield of NO at equilibrium? 
(c) decrease 3O24

For the water–gas shift reaction 
CO1g2 + H2O1g2 ∆ CO21g2 + H21g2, ΔH° = - 41.2 kJ 
does the amount of H2 in an equilibrium mixture increase or decrease when the temperature is increased? How does Kc change when the temperature is decreased? Justify your answers using Le Châtelier’s principle.

Each reaction is allowed to come to equilibrium, and then the volume is changed as indicated. Predict the effect (shift right, shift left, or no effect) of the indicated volume change.
b. PCl3( g) + Cl2( g) ⇌ PCl5( g) (volume is increased)

Consider the following equilibrium:
Ag + 1aq2 + Cl-1aq2 ∆ AgCl1s2
Use Le Châtelier’s principle to predict how the amount of solid silver chloride will change when the equilibrium is disturbed by: (c) Adding NO3, which reacts with Ag + to form the com- plex ion Ag1NH322+

The equilibrium position will not change but the rate will increase.

The equilibrium position will not change but the concentrations of everything will increase.

Which direction will the following reaction (in a 10.0 L flask) proceed if a catalyst is added to the system?&nbsp;CaCO3 (s) &nbsp;⇌ CaO (s) + CO2 (g) &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Kp = 3.2 x 10-28

The equilibrium constant Kc for the gas-phase thermal decom-position of cyclopropane to propene is 1.0 * 105 at 500 K: 
(c) Can you alter the ratio of the two concentrations at equilibrium by adding cyclopropane or by decreasing the volume of the container? Explain.

Addition of a reactant causes the reaction to shift to the right.

Removal of a product causes the reaction to shift to the right.

Decreasing the temperature for an exothermic reaction will cause the reaction to shift to the right.

Correct, changing the volume of the container does not affect this reaction since the number of moles of gaseous product is the same as the number of moles of gaseous reactants.

increasing the concentration of I2

Which of the following will NOT cause the reaction to shift toward the products? H2 (g) + I2 (g) &#8646; 2 HI (g) &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&#916;H = &#8211;9.42 kJ

This reaction is endothermic.
C(s) + CO2(g) ⇌ 2 CO(g)
Predict the effect (shift right, shift left, or no effect) of increasing and decreasing the reaction temperature. How does the value of the equilibrium constant depend on temperature?

The following pictures represent the initial and equilibrium states for the exothermic decomposition of gaseous A mol- ecules (red) to give gaseous B molecules (blue).
(b) Will the number of A molecules in the equilibrium mix- ture increase, decrease, or remain the same after each of the following changes? Explain.
(3) Increasing the pressure by adding an inert gas

For the decomposition reaction PCl51g2 ∆ PCl31g2 + Cl21g2, Kp = 381 at 600 K and Kc = 46.9 at 700 K.
(a) Is the reaction endothermic or exothermic? Explain. Does your answer agree with what you would predict based on bond energies?

A platinum catalyst is used in automobile catalytic convert- ers to hasten the oxidation of carbon monoxide:
2 CO1g2 + O 1g2 ∆Pt 2 CO 1g2 ΔH° = - 566 kJ
Suppose that you have a reaction vessel containing an equilibrium mixture of CO1g2, O21g2, and CO21g2. Under the following conditions, will the amount of CO increase, decrease, or remain the same?
(e) The pressure is increased by adding O2 gas.

Coal, which is primarily carbon, can be converted to natural gas, primarily CH4, by the exothermic reaction:
C(s) + 2 H2(g) ⇌ CH4(g) Which disturbance will favor CH4 at equilibrium?
c. raising the temperature of the reaction mixture

Consider the exothermic reaction:
C2H4(g) + Cl2(g) ⇌ C2H4Cl2(g)
If you were trying to maximize the amount of C2H4Cl2 produced, which tactic might you try? Assume that the reaction mixture reaches equilibrium.
a. increasing the reaction volume
b. removing C2H4Cl2 from the reaction mixture as it forms c. lowering the reaction temperature
d. adding Cl2

Each reaction is allowed to come to equilibrium, and then the volume is changed as indicated. Predict the effect (shift right, shift left, or no effect) of the indicated volume change.
c. CaCO3(s) ⇌ CaO(s) + CO2( g) (volume is increased)

When looking at a chemical reaction we look at the two concepts of Kinetics and Thermodynamics to get a total view. However, remember that Le Chatelier&rsquo;s Principle deals with Thermodynamics and not Kinetics.&nbsp;

Le Chatelier's Principle: Part 2  | Reactions | Chemistry | FuseSchool

Le Chatelier's Principle Part 1 | Reactions | Chemistry | FuseSchool

Baking soda (sodium bicarbonate) decomposes when it is heated:
2 NaHCO31s2 ∆ Na2CO31s2 + CO21g2 + H2O1g2
ΔH° = + 136 kJ
Consider an equilibrium mixture of reactants and products in a closed container. How does the number of moles of CO2 change when the mixture is disturbed by the following:
(b) Adding water vapor

The following picture represents the composition of the equi- librium mixture for the endothermic reaction A2 ∆ 2 A at 500 K. Draw a picture that represents the equilibrium mixture after each of the following changes.
(b) Increasing the volume<img src="https://lightcat-files.s3.amazonaws.com/problem_images/e7316a308240bb8a-1672432939241.jpg" alt="" /><img src="https://lightcat-files.s3.amazonaws.com/problem_images/2c1242e7de3205d2-1678029101263.jpg" alt="" /><img src="https://lightcat-files.s3.amazonaws.com/problem_images/815e9716a37c34d2-1678029101020.jpg" alt="" />

Coal can be used to generate hydrogen gas (a potential fuel) by
the endothermic reaction:
C(s) + H2O(g) ⇌ CO(g) + H2(g)
If this reaction mixture is at equilibrium, predict whether each disturbance will result in the formation of additional hydrogen gas, the formation of less hydrogen gas, or have no effect on the quantity of hydrogen gas. e. adding a catalyst to the reaction mixture

Coal, which is primarily carbon, can be converted to natural gas, primarily CH4, by the exothermic reaction:
C(s) + 2 H2(g) ⇌ CH4(g) Which disturbance will favor CH4 at equilibrium? e. adding a catalyst to the reaction mixture

Methanol 1CH3OH2 can be made by the reaction of CO
with H2:
CO1g2 + 2 H21g2 Δ CH3OH1g2
(c) To maximize the equilibrium yield of methanol,
would you use a high or low pressure?

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10. Periodic Properties of the Elements

11. Bonding & Molecular Structure

12. Molecular Shapes & Valence Bond Theory

13. Liquids, Solids & Intermolecular Forces

14. Solutions

15. Chemical Kinetics

17. Acid and Base Equilibrium

18. Aqueous Equilibrium

19. Chemical Thermodynamics

20. Electrochemistry

21. Nuclear Chemistry

22. Organic Chemistry

23. Chemistry of the Nonmetals

24. Transition Metals and Coordination Compounds

[BOOK CHEM] Clutch Version

Chemical Equilibrium

Most chemical reactions never go to completion where all the reactants are converted into products. Instead these reactions reach a&nbsp;chemical equilibrium.&nbsp;

The Reaction Quotient

The reaction quotient, Q, is used to determine if our chemical reaction is at equilibrium.&#160;