16. Chemical Equilibrium

Chemical Equilibrium

Introduction to Chemical  Equilibrium

The equilibrium constant, K, for 2 NO (g) + O2 (g) ⇌ 2 NO2 (g) is 6.9 x 102.&nbsp;What is the [NO] in an equilibrium mixture of gaseous NO, O2, and NO2 at 500 K that contains 1.5 x 10 –2 M O2 and 4.3 x 10 –3 M NO2?

Calculate Kc for each reaction.
b. CH4(g) + H2O(g) ⇌ CO(g) + 3 H2(g) Kp = 7.7x10^24 (at 298 K)

Find and fix each mistake in the equilibrium constant expressions. a. 2 H2S(g) ⇌ 2 H2(g) + S2(g) K = [H2][S2]/[H2S]

Write an expression for the equilibrium constant of each chemical equation.
a. SbCl5(g) ∆ SbCl3(g) + Cl2(g)

In Section 11.5, we defined the vapor pressure of a liquid in
terms of an equilibrium. 
(b) By using data
in Appendix B, give the value of Kp for this reaction at 30 C.

The following equilibria were measured at 823 K:
CoO1s2 + H21g2 ΔCo1s2 + H2O1g2 Kc = 67
H21g2 + CO21g2 ΔCO1g2 + H2O1g2 Kc = 0.14
(a) Use these equilibria to calculate the equilibrium constant,
Kc, for the reaction CoO1s2 + CO1g2ΔCo1s2
+ CO21g2 at 823 K.

The value of Kc for the reaction of acetic acid with ethanol is 3.4 at 25°C:
CH3CO2H1soln2 + CH3CH2OH1soln2 ∆
Acetic acid Ethanol CH3CO2CH2CH31soln2 + H2O1soln2 Kc = 3.4 (a) How many moles of ethyl acetate are present in an equi- librium mixture that contains 4.0 mol of acetic acid,
6.0 mol of ethanol, and 12.0 mol of water at 25 °C?

The following diagrams represent a hypothetical reaction 
A ¡ B, with A represented by red spheres and B represented 
by blue spheres. The sequence from left to right 
represents the system as time passes. Does the system 
reach equilibrium? If so, in which diagram(s) is the system 
in equilibrium? [Sections 15.1 and 15.2]
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/499cb86a554f2dde-1666358918000.jpg" alt="" />

Consider the equilibrium 
N21g2 + O21g2 + Br21g2 Δ 2 NOBr1g2 
Calculate the equilibrium constant Kp for this reaction, 
given the following information (at 298 K): 
2 NO1g2 + Br21g2Δ2 NOBr1g2 Kc = 2.0 
2 NO1g2ΔN21g2 + O21g2 Kc = 2.1 * 1030

Consider the interconversion of A molecules (red spheres) and B molecules (blue spheres) according to the reaction A ∆ B. Each of the series of pictures at the right represents a separate experiment in which time increases from left to right:
(b) What is the value of the equilibrium constant Kc for the reaction A ∆ B?<img src="https://lightcat-files.s3.amazonaws.com/problem_images/d9fa6ec0efbeafde-1672298490094.jpg" alt="" />

Associated with any reaction at equilibrium is the equilibrium constant K. Its numerical value determines if reactants or products are more greatly favored within a reaction.&nbsp;

Refining petroleum involves cracking large hydrocar- bon molecules into smaller, more volatile pieces. A simple example of hydrocarbon cracking is the gas-phase thermal decomposition of butane to give ethane and ethylene: (a) Write the equilibrium constant expressions for Kp and Kc.

The diagram shown here represents the equilibrium state
for the reaction A21g2 + 2 B1g2 Δ 2 AB1g2. (a) Assuming
the volume is 2 L, calculate the equilibrium constant
Kc for the reaction. [Sections 15.5 and 15.7]
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/e12e2220eeaaba4a-1666359980397.jpg" alt="" />

For each of the equilibria in Problem 15.56, write the equi-librium constant expression for Kp and give the equation that relates Kp and Kc. (a)

Consider a general, single-step reaction of the type A + B ∆ C. Show that the equilibrium constant is equal to the ratio of the rate constants for the forward and reverse reactions, Kc = kf>kr.

Write the expressions for Kc for the following reactions.
In each case indicate whether the reaction is homogeneous
or heterogeneous.
(b) Ti1s2 + 2 Cl21g2 Δ TiCl41l2

Consider the reaction:
N (g) + 3H (g) ⇌ 2NH (g)
Complete the table. Assume that all concentrations are equilib- rium concentrations in M. T (K)
[n2]
[H2]
[nH3]
Kc
500 0.115 0.105 0.439
575 0.110 ________ 0.128
775 0.120 0.140 ________
________
9.6
0.0584

Carbon monoxide replaces oxygen in oxygenated hemoglobin according to the reaction:
HbO2(aq) + CO(aq) ⇌ HbCO(aq) + O2(aq)
a. Use the reactions and associated equilibrium constants at body temperature given here to find the equilibrium con-
stant for the reaction just shown.
Hb(aq) + O2(aq) ⇌ HbO2(aq) Kc = 1.8
Hb(aq) + CO(aq) ⇌ HbCO(aq) Kc = 306

The equilibrium 2 NO1g2 + Cl21g2 Δ 2 NOCl1g2 is
established at 500 K. An equilibrium mixture of the three
gases has partial pressures of 0.095 atm, 0.171 atm, and
0.28 atm for NO, Cl2, and NOCl, respectively. (b) If the vessel has a volume
of 5.00 L, calculate Kc at this temperature.

Calculate Kc for each reaction.
a. I2(g) ⇌ 2I(g) Kp = 6.26 * 10^-22 (at 298K)

A reaction reaches equilibrium once the rate of the forward reaction equals the rate of the reverse reaction. Once at equilibrium there is no net change in the concentration of reactants or products.&nbsp;

Hess’s Law and the Equilibrium Constant K

Consider the following reaction:
H2(g) + I2(g) ⇌ 2 HI(g) Complete the table. Assume that all concentrations are equilib- rium concentrations in M. T (°C)
[H2]
[i2]
[Hi]
Kc
25 0.0355 0.0388
340 ________ 0.0455
445 0.0485 0.0468
0.922 ________
0.387 9.6
________ 50.2

Whereas the rate constant, k, is affected by factors dealing with the rate of reaction, the equilibrium constant, K, is affected by only temperature.&nbsp;

At 80 C, Kc = 1.87 * 10-3 for the reaction
PH3BCl31s2 Δ PH31g2 + BCl31g2
(a) Calculate the equilibrium concentrations of PH3 and
BCl3 if a solid sample of PH3BCl3 is placed in a closed vessel
at 80 C and decomposes until equilibrium is reached.

The decomposition of nitrogen monoxide can be achieved under high temperatures to create the products of nitrogen and oxygen gas.&nbsp;6 NO(aq) ⇌ 3 N2(aq) + 3 O2(aq)&nbsp;a) What is the equilibrium equation for the reaction above?b) What is the equilibrium expression for the reverse reaction.&nbsp;

The equilibrium constant for the dissociation of molecular
iodine, I21g2Δ2 I1g2, at 800 K is Kc = 3.1 * 10-5.
(b) Assuming both forward and reverse reactions are
elementary processes, which reaction has the larger rate
constant, the forward or the reverse reaction?

The old concept of <a href="https://www.clutchprep.com/chemistry/hess-law">Hess’s Law</a> can be applied to our new concept of the Equilibrium Constant K.&nbsp;

Equilibrium: Crash Course Chemistry #28

Write the expressions for Kc for the following reactions.
In each case indicate whether the reaction is homogeneous
or heterogeneous.
(g) 2 C8H181l2 + 25 O21g2 Δ 16 CO21g2 + 18 H2O1l2

The concept of chemical equilibrium is very important.
Which one of the following statements is the most correct
way to think about equilibrium?
(a) If a system is at equilibrium, nothing is happening.
(b) If a system is at equilibrium, the rate of the forward reaction
is equal to the rate of the back reaction.
(c) If a system is at equilibrium, the product concentration is
changing over time.

15.1 Equilibrium and Equilibrium Constants | General Chemistry

Methane (CH4) reacts with hydrogen sulfide to yield hydrogen gas and carbon disulfide, a solvent used in the manufacturing rayon and cellophane. What is the value of Kc at 1000 K if the partial pressures in an equilibrium mixture at 1000 K are 0.20 atm methane, 0.15 atm hydrogen sulfide, 0.30 atm carbon disulfide and 0.10 atm hydrogen gas?&nbsp;CH4 (g) + 2 H2S (g) ⇌ 4 H2 (g) + CS2 (g)

The value of Kc for the reaction 3 O21g2 ∆ 2 O31g2 is 1.7 * 10-56 at 25°C. Do you expect pure air at 25 °C to contain much O3 (ozone) when O2 and O3 are in equilib- rium? If the equilibrium concentration of O2 in air at 25 °C is 8 * 10-3 M, what is the equilibrium concentration of O3?

Identify the true statement about the rate of the forward and reverse reaction once a reaction has reached equilibrium. (a) The rate of the forward reaction and the reverse reaction is zero. (b) The rate of the forward reaction is greater than the rate of the reverse reaction. 
(c) The rate of the reverse reaction is greater than the rate of the forward reaction. 
(d) The rate of the forward reaction is equal to the rate of the reverse reaction.

Which of the following relative values of kf and kr results in an equilibrium mixture that contains large amounts of reactants and small amounts of products? (a) kf 7 kr (b) kf = kr (c) kf 6 kr

When this reaction comes to equilibrium, will the concentra- tions of the reactants or products be greater? Does the answer to this question depend on the initial concentrations of the reac- tants and products?
A(g)+B(g) ⇌ 2C(g) Kc = 1.4x10^-5

Determination of the value for &Delta;n can help us determine if Kp is greater than, less than or equal to Kc.&nbsp;

Which one of the following statements does not describe the equilibrium state?a. While at equilibrium, a dynamic process is still occurring. &nbsp;b. The concentration of the reactants is equal to the concentration of the products.c. The concentration of the reactants and products reach a constant level.d. At equilibrium, the net concentration of all species is not changing.e. All are true.

Consider the reaction of chloromethane with OH- in aque- ous solution: 
CH Cl1aq2 + OH-1aq2 ∆kf CH OH1aq2 + Cl-1aq2 
At 25 °C, the rate constant for the forward reaction is 6 * 10-6 M-1 s-1, and the equilibrium constant Kc is 1 * 1016. Calculate the rate constant for the reverse reac- tion at 25 °C.

Phosphorus trichloride gas and chlorine gas react to form
phosphorus pentachloride gas: PCl31g2 + Cl21g2 Δ
PCl51g2. A 7.5-L gas vessel is charged with a mixture of
PCl31g2 and Cl21g2, which is allowed to equilibrate at 450
K. At equilibrium the partial pressures of the three gases are
PPCl3 = 0.124 atm, PCl2 = 0.157 atm, and PPCl5 = 1.30 atm.
(a) What is the value of Kp at this temperature?

The vapor pressure of water at 25 °C is 0.0313 atm. Cal- culate the values of Kp and Kc at 25 °C for the equilibrium H2O1l2 ∆ H2O1g2.

At 900 K, the following reaction has Kp = 0.345: 
2 SO21g2 + O21g2 Δ 2 SO31g2 
In an equilibrium mixture the partial pressures of SO2 and O2 
are 0.135 atm and 0.455 atm, respectively. What is the equilibrium 
partial pressure of SO3 in the mixture?

At 1000 K, Kp = 1.85 for the reaction
SO21g2 + 12O21g2 Δ SO31g2
(c) What is the value of Kc for the reaction in part (b)?

Consider the reaction: SO2Cl2(g) ⇌ SO2(g) + Cl2(g) Kp = 2.91*10^3 at 298 K
In a reaction at equilibrium, the partial pressure of SO2 is 137 torr and that of Cl2 is 285 torr. What is the partial pressure of SO2Cl2 in this mixture?

In Section 11.5, we defined the vapor pressure of a liquid in
terms of an equilibrium. 
(c) What is the value of Kp for any liquid in equilibrium with
its vapor at the normal boiling point of the liquid?

Consider the sublimation of mothballs at 27 °C in a room having dimensions 8.0 ft * 10.0 ft * 8.0 ft. Assume that the mothballs are pure solid naphthalene 1density 1.16 g>cm32
and that they are spheres with a diameter of 12.0 mm. The equilibrium constant Kc for the sublimation of naphthalene is
5.40 * 10-6 at 27 °C.
C10H81s2 ∆ C10H81g2
(b) How many mothballs are required to saturate the room with gaseous naphthalene?

Hess's Law & Equilibrium Constant K

The equilibrium constant K is a ratio of products to reactants. It only deals with gaseous or aqueous compounds.&nbsp;

Chemical Equilibrium Constant K - Ice Tables - Kp and Kc

Calculate Kp for each reaction.
b. N2(g) + 3H2(g) ⇌ 2NH3(g) Kc = 3.7x10^8 (at 298 K)

At 373 K, Kp = 0.416 for the equilibrium 
2 NOBr1g2 Δ 2 NO1g2 + Br21g2 
If the pressures of NOBr(g) and NO(g) are equal, what is 
the equilibrium pressure of Br21g2?

For each of the following equilibria, write the equilibrium constant expression for Kc. Where appropriate, also write the equilibrium constant expression for Kp. (a) Fe2O31s2 + 3 CO1g2 ∆ 2 Fe1l2 + 3 CO21g2

Find and fix each mistake in the equilibrium constant expressions. b. CO(g) + Cl2(g) ⇌ COCl2(g) K = [CO][Cl2]/[COCl2]

Which of the following reactions yield appreciable equilib- rium concentrations of both reactants and products?
(a) 2 Cu1s2 + O21g2 ∆ 2 CuO1s2; Kc = 4 * 1045

Given the hypothetical reaction 2 A (s) + ? B (g) ⇌ 3 C (g), Kp = 0.0105 and Kc = 0.45 at 250 degrees Celsius. What is the value of the coefficient of B?&nbsp;

Ozone is unstable with respect to decomposition to ordi-nary oxygen:
2 O31g2 ∆ 3 O21g2 Kp = 1.3 * 1057
How many O3 molecules are present at equilibrium in 10 mil-lion cubic meters of air at 25 °C and 720 mm Hg pressure?

When dealing with equilibrium units in terms of pressure the equilibrium constant of Kp must be used, but if the equilibrium units are in molarity then we must use the equilibrium constant of Kc.&nbsp;

Write the expression for Kc for the following reactions. In
each case indicate whether the reaction is homogeneous
or heterogeneous.
(e) 2 Ag1s2 + Zn2+1aq2 Δ 2 Ag+1aq2 + Zn1s2

In which of the given reactants is Kp greater than, less than and equal to Kc?a) SO3 (g) + NO (g) ⇌ SO2 (g) + NO2 (g)b) P4 (s) + 5 O4 (g) ⇌ P4O10 (s)c) 4 NH3 (g) + 3 O2 (g) ⇌ 2 N2 (g) + 6 H2O (g)

At 218 C, Kc = 1.2 * 10-4 for the equilibrium 
NH4SH1s2 Δ NH31g2 + H2S1g2 
Calculate the equilibrium concentrations of NH3 and H2S 
if a sample of solid NH4SH is placed in a closed vessel at 
218 C and decomposes until equilibrium is reached.

Consider the reaction:
2NO(g) + Br2(g) ⇌ 2NOBr(g) Kp = 28.4 at 298K
In a reaction mixture at equilibrium, the partial pressure of NO is 108 torr and that of Br2 is 126 torr. What is the partial pressure of NOBr in this mixture?

GCSE Chemistry - Reversible Reactions and Equilibrium #49

Consider the sublimation of mothballs at 27 °C in a room having dimensions 8.0 ft * 10.0 ft * 8.0 ft. Assume that the mothballs are pure solid naphthalene 1density 1.16 g>cm32
and that they are spheres with a diameter of 12.0 mm. The equilibrium constant Kc for the sublimation of naphthalene is
5.40 * 10-6 at 27 °C.
C10H81s2 ∆ C10H81g2
(a) When excess mothballs are present, how many gaseous naphthalene molecules are in the room at equilibrium?

At 80 C, Kc = 1.87 * 10-3 for the reaction
PH3BCl31s2 Δ PH31g2 + BCl31g2
(b) If the flask has a volume of 0.250 L, what is the minimum
mass of PH3BCl31s2 that must be added to the flask
to achieve equilibrium?

Kp and Kc are related to one another by the following equation below:&nbsp;

H2 and I2 are combined in a flask and allowed to react according to the reaction:
H2(g) + I2(g) ⇌ 2 HI(g)
Examine the figures (sequential in time) and answer the questions: a. Which figure represents the point at which equilibrium is
reached?

The following diagram represents a reaction shown going
to completion. Each molecule in the diagram represents
0.1 mol, and the volume of the box is 1.0 L. (d) Assuming that all of the molecules are in
the gas phase, calculate n, the change in the number of
gas molecules that accompanies the reaction. [Section 15.2]
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/aba749bb87dc7daf-1666352758708.jpg" alt="" />

An equilibrium mixture of N2, H2, and NH3 at 700 K con- tains 0.036 M N2 and 0.15 M H2. At this temperature, Kc for the reaction N21g2 + 3 H21g2 ∆ 2 NH31g2 is 0.29. What is the concentration of NH3?

State which is greater in amount:reactants or products, based on the given equilibrium constant, K.&nbsp;<img src="https://static.studychannel-prd.pearsonprd.tech/courses/general-chemistry/thumbnails/images/c83f0cf8"alt=""/>

In Section 11.5, we defined the vapor pressure of a liquid in
terms of an equilibrium. (a) Write the equation representing
the equilibrium between liquid water and water vapor
and the corresponding expression for Kp.

The equilibrium constant Kc for the gas-phase thermal decom-position of cyclopropane to propene is 1.0 * 105 at 500 K: <img src="https://lightcat-files.s3.amazonaws.com/problem_images/84a2a7fd9805de8a-1672252748164.jpg" alt="" /> (a) What is the value of Kp at 500 K?

What Is Dynamic Equilibrium? | Reactions | Chemistry | FuseSchool

Ethene (C2H4) can be halogenated by this reaction:
C2H4(g) + X2(g) ⇌ C2H4X2(g)
where X2 can be Cl2 (green), Br2 (brown), or I2 (purple). Examine the three figures representing equilibrium concentrations in this reaction at the same temperature for the three different hal- ogens. Rank the equilibrium constants for the three reactions from largest to smallest. <img src="https://lightcat-files.s3.amazonaws.com/problem_images/283c54ef29f90736-1674579927689.jpg" alt="" />

Suppose that the gas-phase reactions A ¡ B and
B ¡ A are both elementary processes with rate constants
of 4.7 * 10-3 s-1 and 5.8 * 10-1 s-1, respectively. (b) Which is greater at equilibrium,
the partial pressure of A or the partial pressure of B?

The equilibrium 2 NO1g2 + Cl21g2 Δ 2 NOCl1g2 is
established at 500 K. An equilibrium mixture of the three
gases has partial pressures of 0.095 atm, 0.171 atm, and
0.28 atm for NO, Cl2, and NOCl, respectively. (a) Calculate
Kp for this reaction at 500.0 K.

The following picture represents the equilibrium state for the reaction 2 AB ∆ A2 + B2.  Which rate constant is larger, kf or kr? Explain.

A chemist trying to synthesize a particular compound attempts two different synthesis reactions. The equilibrium constants for the two reactions are 23.3 and 2.2 * 104 at room temperature. However, upon carrying out both reactions for 15 minutes, the chemist finds that the reaction with the smaller equilibrium constant produces more of the desired product. Explain how this might be possible.

Equilibrium and Equilibrium Constants

Which of the following statements are true and which are
false? (c) As the value of the equilibrium constant
increases, the speed at which a reaction reaches equilibrium
increases.

Reversing a reaction gives us the reciprocal of K, while multiplying a reaction by a value makes it the power for K.&nbsp;

At 25 C, the reaction 
CaCrO41s2ΔCa2+1aq2 + CrO4 
2-1aq2 
has an equilibrium constant Kc = 7.1 * 10-4. What are 
the equilibrium concentrations of Ca2 + and CrO4 
2- in a 
saturated solution of CaCrO4?

Chemical Equilibria and Reaction Quotients

Calculate Kp for each reaction.
a. N2O4(g) ⇌ 2NO2(g) Kc = 5.9x10^-3 (at 298 K)

For the general, single-step reaction A1g2 + B1g2 ∆ AB1g2, Kc = 4.5 * 10-6, which of the following statements is true? (LO 15.16) 
(a) Ea 1forward2 6 Ea 1reverse2 
(b) The equilibrium mixture contains mostly products. 
(c) kr 7 kf 
(d) The reaction is exothermic.

If Kc = 0.042 for PCl31g2 + Cl21g2 Δ PCl51g2 at 500 K, 
what is the value of Kp for this reaction at this temperature?

Which of the following reactions lies to the right, favoring
the formation of products, and which lies to the left,
favoring formation of reactants?
(b) 2 HBr1g2 Δ H21g2 + Br21g2 Kc = 5.8 * 10-18

For the reaction A2 + 2B ∆ 2 AB, the rate of the for- ward reaction is 18 M/s and the rate of the reverse reaction is 12 M/s. The reaction is not at equilibrium. Will the reaction pro-
ceed in the forward or reverse direction to attain equilibrium?

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Chad's Prep

1. Intro to General Chemistry

2. Atoms & Elements

3. Chemical Reactions

4. BONUS: Lab Techniques and Procedures

5. BONUS: Mathematical Operations and Functions

6. Chemical Quantities & Aqueous Reactions

7. Gases

8. Thermochemistry

9. Quantum Mechanics

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

Le Chatelier's Principle

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;