16. Chemical Equilibrium

ICE Chart

Equilibrium Calculations 2: Equilibrium Concentrations

At 1000 K, the value of Kc for the reaction C1s2 + H2O1g2 ∆ CO1g2 + H21g2 is 3.0 * 10-2. Calculate the equilibrium concentrations of H2O, CO2, and H2 in a reac- 
tion mixture obtained by heating 6.00 mol of steam and an excess of solid carbon in a 5.00-L container. What is the molar composition of the equilibrium mixture?

For the equilibrium 
Br21g2 + Cl21g2 Δ 2 BrCl1g2 
at 400 K, Kc = 7.0. If 0.25 mol of Br2 and 0.55 mol of Cl2 
are introduced into a 3.0-L container at 400 K, what will 
be the equilibrium concentrations of Br2, Cl2, and BrCl?

Carbon monoxide and chlorine gas react to form phosgene: CO(g) + Cl2(g) ⇌ COCl2(g) Kp = 3.10 at 700 K
If a reaction mixture initially contains 215 torr of CO and 245 torr of Cl2, what is the mole fraction of COCl2 when equilibrium is reached?

15.3 Equilibrium Calculations (ICE Tables) | General Chemistry

Equilibrium Equations: Crash Course Chemistry #29

ICE Charts

A 0.831-g sample of SO3 is placed in a 1.00-L container 
and heated to 1100 K. The SO3 decomposes to SO2 and O2: 
2 SO31g2 Δ 2 SO21g2 + O21g2 
At equilibrium, the total pressure in the container is 1.300 
atm. Find the values of Kp and Kc for this reaction at 1100 K.

For the reaction shown here, Kc = 255 at 1000 K. CO(g) + Cl2(g) ⇌ COCl2(g)
If a reaction mixture initially contains a CO concentration of 0.1500 M and a Cl2 concentration of 0.175 M at 1000 K, what are the equilibrium concentrations of CO, Cl2, and COCl2 at 1000 K?

The following equilibria were measured at 823 K:
CoO1s2 + H21g2 ΔCo1s2 + H2O1g2 Kc = 67
H21g2 + CO21g2 ΔCO1g2 + H2O1g2 Kc = 0.14
(d) If the reaction
vessel from part (c) is heated to 823 K and allowed to
come to equilibrium, how much CoO1s2 remains?

Correct, the reaction was reversed and amount doubled.

The amounts of reactants and products were doubled.

 If the chemical equation is modified in some way, the equilibrium constant for the equation must be changed to reflect the modification. 

If Kc for the following reaction is 5.4 &#215; 1013, 2 NO (g) + O2 (g) &#8646; 2 NO2 (g) what is Kc for the reaction shown below? 4 NO2 (g) &#8646; 4 NO (g) + 2 O2 (g)

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: (c) A sample of butane having a pressure of 50 atm is heated at 500 °C in a closed container at constant volume. When equilibrium is reached, what percentage of the butane has been converted to ethane and ethylene? What is the total pressure at equilibrium?

When 0.600 atm of NO­­2 was allowed to come to equilibrium the total pressure was 0.875 atm

A 14.58 g quantity of N2O4 was placed in a 1.000-L reaction vessel at 400 K. The N2O4 decomposed to an equilibrium mix- ture of N2O4 and NO2 that had a total pressure of 9.15 atm.
(b) How much heat (in kilojoules) was absorbed when the N2O4 decomposed to give the equilibrium mixture? (Stan- dard heats of formation may be found in Appendix B.)

If Kc is 32.7 at 300oC for the reaction below

Heavy water, symbolized D2O 1D = 2H2 finds use as a neutron moderator in nuclear reactors. In a mixture with ordinary water, exchange of isotopes occurs according to the following equation: 
H2O + D2O ∆ 2 HDO Kc = 3.86 at 298 K 
When 1.00 mol of H2O is combined with 1.00 mol of D2O, what are the equilibrium amounts of H2O, D2O, and HDO (in moles) at 298 K? Assume the density of the mixture is constant at 1.05 g>cm3.

Consider the reaction and the associated equilibrium constant: aA(g) ⇌ bB(g) Kc = 4.0
Find the equilibrium concentrations of A and B for each value of a and b. Assume that the initial concentration of A in each case is 1.0 M and that no B is present at the beginning of the reaction. c. a=1;b=2

The equilibrium constant Kc for C1s2 + CO21g2Δ
2 CO1g2 is 1.9 at 1000 K and 0.133 at 298 K.
(b) If excess 
C is allowed to react with 25.0 g of CO2 in a 3.00-L vessel 
at 1000 K, how many grams of C are consumed?

At 650 K, the reaction MgCO3(s) ⇌ MgO(s) + CO2(g) has Kp = 0.026. A 10.0-L container at 650 K has 1.0 g of MgO(s) and CO2 at P = 0.0260 atm. The container is then compressed to a volume of 0.100 L. Find the mass of MgCO3 that is formed.

The F ¬ F bond in F2 is relatively weak because the lone pairs of electrons on one F atom repel the lone pairs on the other F atom; Kp = 7.83 at 1500 K for the reaction F21g2 ∆ 2 F1g2.
(b) What fraction of the F2 molecules dissociate at 1500 K?

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
(a) Calculate Kc for this reaction at this temperature.

At 100 °C, Kc = 4.72 for the reaction 2 NO21g2 ∆ N2O41g2. An empty 10.0-L flask is filled with 4.60 g of NO2 at 100 °C. What is the total pressure in the flask at equilibrium?

The coefficients in the equation must be considered.

The concentration of all species must be considered along with the coefficients.

The coefficients in the equation must be considered using the forward reaction.

This value is the reaction quotient for the reverse reaction.

 The reaction quotient is the ratio&#8211;at any point in the reaction&#8211;of the concentrations of the products raised to their stoichiometric coefficients divided by the concentrations of the reactants raised to their stoichiometric coefficients. 

Calculate the reaction quotient for the reaction below where the concentrations are [SO3] = 0.500 M, [SO2] = 0.0500 M, and [O2] = 0.100 M. 2 SO3 (g) &#8646; 2 SO2 (g) + O2 (g)

When Q > K, the reaction will shift toward the reactant side.

If Q > K, there is too much product present.

When Q = K, the reaction has stopped.

Correct, when Q = K, the system is at equilibrium.

When Q < K, the reaction will shift toward the product side.

If Q < K, there is too much reactant present.

When Q = K, the forward reaction rate equals the reverse reaction rate.

When Q = K, the system is at equilibrium.

Q is the reaction quotient at any point in the reaction.

Which of the following is a false statement about the relationship between Q and K?

For the reaction:N2 (g) + 2 O2 (g) ⇌ 2 NO2 (g), Kc = 8.3 x 10&nbsp;-10 at 25°C. What is the concentration of N2 gas at equilibrium when the concentration of NO2 is twice the concentration of O2 gas?

The industrial solvent ethyl acetate is produced by the reac-tion of acetic acid with ethanol:
CH3CO2H1soln2 + CH3CH2OH1soln2 ∆
CH3CO2CH2CH31soln2 + H2O1soln2
Ethyl acetate (b) A solution prepared by mixing 1.00 mol of acetic acid and 1.00 mol of ethanol contains 0.65 mol of ethyl ace- tate at equilibrium. Calculate the value of Kc. Explain why you can calculate K without knowing the volume of the solution.

For the reaction shown here, Kc = 0.513 at 500 K. N2O4(g) ⇌ 2NO2(g)
If a reaction vessel initially contains an N2O4 concentration of 0.0500 M at 500 K, what are the equilibrium concentrations of N2O4 and NO2 at 500 K?

In order to calculate the equilibrium concentrations of compounds we need to use an ICE Chart.&nbsp;

An important reaction in the formation of acid rain listed below.2 SO2 (g)   +  O2 (g)  ⇌  2 SO3 (g)Initially, 0.023 M SO2 and 0.015 M O2 are mixed and allowed to react in an evacuated flask at 340 oC

An ICE Chart should be used when we are missing more than one equilibrium amount for compounds in our balanced equation.&nbsp;

The equilibrium constant is a ratio of products to reactants and the coefficients in the equation must be considered.

The equilibrium constant is a ratio of products to reactants. This value is the Kc for the reverse reaction.

 The equilibrium constant is the concentrations of the products raised to their stoichiometric coefficients divided by the concentrations of the reactants raised to their stoichiometric coefficients. 

Calculate Kc for the following reaction at 300 K where the equilibrium concentrations are [SO3] = 0.400 M, [SO2] = 0.200 M, and [O2] = 0.600 M. 2 SO3 (g) &#8646; 2 SO2 (g) + O2 (g)

Consider the hypothetical reaction A1g2 + 2 B1g2 Δ
2 C1g2, for which Kc = 0.25 at a certain temperature. A
1.00-L reaction vessel is loaded with 1.00 mol of compound
C, which is allowed to reach equilibrium. Let the
variable x represent the number of mol>L of compound
A present at equilibrium.
(e) From the plot in part (d), estimate the equilibrium concentrations of A, B, and C. (Hint: You can check the accuracy of your answer by
substituting these concentrations into the equilibrium
expression.)

The reaction of fumarate with water to form L-malate is catalyzed by the enzyme fumarase; Kc = 3.3 at 37°C. When a reaction mixture with [fumarate] = 1.56 * 10-3 M and [l -malate] = 2.27 * 10-3 M comes to equilibrium in the presence of fumarase at 37 °C, what are the equilibrium concentrations of fumarate and L-malate? (Water can be omit- ted from the equilibrium equation because its concentration in dilute solutions is essentially the same as that in pure water.)

Practice Problem: ICE Box Calculations

Equilibrium Calculations 1: Equilibrium Constants

We place 2.5 mol of CO and 2.5 mol of CO3 in a 10.0 L flask and let the system come to equilibrium

Consider the reaction:
A(g) ⇌ B(g) + C(g)
Find the equilibrium concentrations of A, B, and C for each value of Kc. Assume that the initial concentration of A in each case is 1.0 M and that the reaction mixture initially contains no products. Make any appropriate simplifying assumptions.
b. Kc = 0.010

Consider the reaction:
SO2Cl2(g) ⇌ SO2(g) + Cl2(g)
Kc = 2.99 * 10-7 at227°C
If a reaction mixture initially contains 0.175 M SO2Cl2, what is the equilibrium concentration of Cl2 at 227 °C?

At 70 K, CCl4 decomposes to carbon and chlorine. The Kp for the decomposition is 0.76. Find the starting pressure of CCl4 at this temperature that will produce a total pressure of 1.0 atm at
equilibrium.

A 79.2 g chunk of dry ice (solid CO2) and 30.0 g of graphite (carbon) were placed in an empty 5.00-L container, and the mixture was heated to achieve equilibrium. The reaction is
CO 1g2 + C s ∆ 2 CO g
(b) What is the value of Kp at 1100 K if the gas density at 1100 K is 16.9 g/L?

The equilibrium constant Kc for the reaction N21g2 + 3 H21g2 ∆ 2 NH31g2 is 4.20 at 600 K. When a quantity of gaseous NH3 was placed in a 1.00-L reaction vessel at 
600 K and the reaction was allowed to reach equilibrium, the vessel was found to contain 0.200 mol of N2. How many moles of NH3 were placed in the vessel?

Recalculate the equilibrium concentrations in Problem 15.93 if the initial concentrations are 2.24 M N2 and 0.56 M O2. (This N2>O2 concentration ratio is the ratio found in air.)

Acetic acid tends to form dimers, 1CH3CO2H22, because of hydrogen bonding: The equilibrium constant Kc for this reaction is 1.51 * 102 in benzene solution but only 3.7 * 10-2 in water solution.
(a) Calculate the ratio of dimers to monomers for 0.100 M acetic acid in benzene.

Consider the reaction:
HC2H3O2(aq) + H2O(l) ⇌ H3O+(aq) + C2H3O2-(aq)
Kc = 1.8 * 10-5 at25°C If a solution initially contains 0.210 M HC2H3O2, what is the
equilibrium concentration of H3O + at 25 °C?

At a given temperature the gas phase reaction:N2 (g) + O2 (g) ⇌ 2 NO (g) has an equilibrium constant of 4.00 x 10 -15. What will be the concentration of NO at equilibrium if 2.00 moles of nitrogen and 6.00 moles oxygen are allowed to come to equilibrium in a 2.0 L flask.

Vinegar contains acetic acid, a weak acid that is partially dissociated in aqueous solution:
CH3CO2H1aq2 ∆ H+ 1aq2 + CH3CO-1aq2  (b) What is the value of Kc if the extent of dissociation in
1.0 M CH3CO2H is 0.42%?

At 700 K, the equilibrium constant for the reaction
CCl41g2 Δ C1s2 + 2 Cl21g2
is Kp = 0.76. A flask is charged with 2.00 atm of CCl4,
which then reaches equilibrium at 700 K. 
(b) What are the partial pressures of CCl4 and Cl2 at equilibrium?

Understanding an ICE Chart 

We have a solution where Ag(CN)2 –(g), CN – (g), and Ag+ (g) have an equilibrium constant, K, equal to 1.8 x 10-19. If the equilibrium concentrations of Ag(CN)2 – and CN – are 0.030 and 0.10 respectively, what is the equilibrium concentration of Ag+

A reaction vessel at 27 °C contains a mixture of SO2 (P = 3.00 atm) and O2 (P = 1.00 atm). When a catalyst is added, this reaction takes place: 2 SO2( g) + O2( g) ⇌ 2 SO3( g). At
equilibrium, the total pressure is 3.75 atm. Find the value of Kc.

A mixture of 0.2000 mol of CO2, 0.1000 mol of H2, and
0.1600 mol of H2O is placed in a 2.000-L vessel. The following
equilibrium is established at 500 K:
CO21g2 + H21g2 Δ CO1g2 + H2O1g2
(d) Calculate Kc for the reaction.

The Quadratic Formula

Since our equilibrium constant K is involved in an ICE Chart then we must continue to ignore solids and liquids.&nbsp;

The equilibrium constant for the dimerization of acetic acid in benzene solution is 1.51 * 102 at 25 °C.
2 CH3CO2H ∆ 1CH3CO2H22 Kc = 1.51 * 102 at 25 °C
(b) What is the osmotic pressure of the solution at 25 °C?

The equilibrium constant for the reaction SO2(g) + NO2(g)
⇌ SO3(g) + NO(g) is Kc = 3.0. Find the amount of NO2 that must be added to 2.4 mol of SO2 in order to form 1.2 mol of SO3 at equilibrium.

At 2000 C, the equilibrium constant for the reaction 
2 NO1g2 Δ N21g2 + O21g2 
is Kc = 2.4 * 103. If the initial concentration of NO is 
0.175 M, what are the equilibrium concentrations of NO, 
N2, and O2?

Chemical Equilibria and Reaction Quotients

Acetic acid tends to form dimers, 1CH3CO2H22, because of hydrogen bonding: The equilibrium constant Kc for this reaction is 1.51 * 102 in benzene solution but only 3.7 * 10-2 in water solution.
(b) Calculate the ratio of dimers to monomers for 0.100 M acetic acid in water.

The number of moles of gaseous products is equal to the number of moles of gaseous reactants (&Delta;n = 0).

 Think about the relative number of moles of gas on the product and reactant side of the equation. 

The following reaction has a Kc value of 4.1 &#215; 10-31 at 25 &#186;C. Calculate Kp at this temperature.N2 (g) + O2 (g) &#8646; 2 NO (g)

For the decomposition reaction PCl51g2 ∆ PCl31g2 + Cl21g2, Kp = 381 at 600 K and Kc = 46.9 at 700 K.
(b) If 1.25 g of PCl5 is introduced into an evacuated 0.500-L flask at 700 K and the decomposition reaction is allowed to reach equilibrium, what percent of the PCl5 will decompose and what will be the total pressure in the flask?

For the equilibrium
PH3BCl31s2 Δ PH31g2 + BCl31g2
Kp = 0.052 at 60 C. 
(b) After 3.00 g of
solid PH3BCl3 is added to a closed 1.500-L vessel at 60 C,
the vessel is charged with 0.0500 g of BCl31g2. What is the
equilibrium concentration of PH3?

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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

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;