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Wize University Chemistry Textbook > Equilibrium

The Equilibrium Constant (K)

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Equilibrium Constant (K)

To define the extent to which equilibrium favors one side of the reaction over the other, we can use the Equilibrium Constant.

Given the model reaction:
aA+bB⇌cC+dD\large{aA +bB \rightleftharpoons cC + dD}
A & B are reactants and C & D are products.
a,b,c,d are their stoichiometric coefficients


The Equilibrium Expression (in terms of concentration) can be written as:


Kc=[ Products][Reactants]=[C]c[D]d[A]a[B]b\large\boxed{K_c=\frac{\left[\ Products\right]}{\left[Reactan ts\right]}=\frac{\left[C\right]^c\left[D\right]^d}{\left[A\right]^a\left[B\right]^b}}


The equilibrium constant (K) is a ratio used to describe the relative concentrations of products and reactants at equilibrium!
You may also see it called the Law of Mass Action.


Examples:
Keq (at equilibrium), Ka (for acids), Kb (for bases), Kw (for water), Ksp (solubility product constant)

Wize Concept
K can have different subscripts, but all K's follow the same rules!

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Example: What is the K expression for the reaction below?

N2(g) + 3H2(g) ⇌ 2NH3(g)


Wize Tip
Since coefficients become exponents in the K expression, we need to make sure that our equation is balanced!


K= [NH3]2[N2][H2]3\frac{\left[NH_3\right]^2}{\left[N_2\right]\left[H_2\right]^3}

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Additional Notes About K:

1) Above we wrote Kc. The c stands for concentration because we are considering the concentrations of the species in mol/L.

2) If instead we were considering gases and their pressures in atm, then we would write Kp!

Example: What is the Kp expression for the following reaction?

2SO2(g) + O2(g) ⇌ 2SO3(g)



Kp=(PSO3)2(PSO2)2(PO2)Kp=\frac{\left(PSO_3^{ }\right)^2}{\left(PSO_2\right)^2\left(PO_2\right)}


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3) If any species in the reaction are solids (s) or liquids (l), their concentrations do not affect equilibrium and therefore they do not appear in the equilibrium expression!

Example: What is the equilibrium expression for the following reaction?

PbCl2(s) ⇌ Pb2+ (aq) + 2Cl- (aq)

K= [Pb2+][Cl-]2


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4) We will see that changes in volume, pressure, temperature, and concentration can shift the equilibrium (according to Le Chatelier's Principle)

But the only factor that will change K is temperature!



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The Magnitude of the Equilibrium Constant, K

K tells us which side of the reaction (products or reactants) are favored and to what extent.

Example:
If we had the K value 1.8x1010 would products or reactants be favored at equilibrium?
Products!

Since there is an exponent of 10, then (products/reactants)
products
are favored to a (small/great)
great
extent!




Example:
If K was 1.2x10-8 then are products or reactants favored at equilibrium? And to a great or small extent?

Reactants
are favored to a
great
extent!

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Example: Are products or reactants favored at equilibrium according to the following reaction and concentration time graph?

2SO2(g) + O2(g) ⇌ 2SO3(g)

Photo by OpenStax / CC BY

Products are favored at equilibrium since at equilibrium (when the concentrations start to get flat in the graph), there is a higher concentration of SO3 (a product) than the reactants.

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Summary of What K Tells Us

Kc=[ Products][Reactants]\large{K_c=\frac{\left[\ Products\right]}{\left[Reactan ts\right]}}

Keq > 1

  • At equilibrium, products/reactants are favored:
    products
  • This is because products/reactants are more stable:
    products
  • As a result, at equilibrium there will be more reactants, more products, or equal amounts of products and reactants:
    more products

Keq = 1

  • At equilibrium, products/reactants are favored:
    neither
  • This is because products/reactants are more stable:
    equally stable
  • As a result, at equilibrium there will be more reactants, more products, or equal amounts of products and reactants:
    equal amounts

Keq < 1

  • At equilibrium, products/reactants are favoured:
    reactants
  • This is because products/reactants are more stable:
    reactants
  • As a result, at equilibrium there will be more reactants, more products, or equal amounts of products and reactants:
    more reactants

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Practice: Writing Equilibrium Constants

Which of the following expression is the correct equilibrium-constant expression for the reaction below?

HF(aq) + H2O(l) ⇌ H3O+(aq) + F-(aq)

1.
Kc=[HF][H2O][H3O+][F−]K_c=\frac{[HF][H_2O]}{[H_3O^+][F^-]}
2.
Kc=1[HF]K_c=\frac{1}{[HF]}
3.
Kc=[H3O+][F−][HF][H2O]K_c=\frac{[H_3O^+][F^-]}{[HF][H_2O]}
4.
Kc=[H3O+][F−][HF]K_c=\frac{[H_3O^+][F^-]}{[HF]}
5.
Kc=[F−][HF]K_c=\frac{[F^-]}{[HF]}




Practice: Calculating the Equilibrium Constant

For the process:
N2 (g) + 3 H2 (g) ⇌ 2 NH3 (g)

Determine the value of Kc when an equilibrium mixture contains 0.0420 mol N2, 0.516 mol H2, and 0.0357 mol NH3 in a 1.00 liter container at 400oC.

Extra Practice
Equilibrium
Consider the following equilibria:
2HCl(g)⇌H2(g)+Cl2(g)Kc,12HCl_{(g)} \rightleftharpoons H_{2(g)} +Cl_2{(g)} \hspace{20pt} K_c,1
2H2S2(g)⇌2H2(g)+S2(g)Kc,22H_2S_2{(g)} \rightleftharpoons 2H_{2(g)} +S_2{(g)} \hspace{20pt} K_c,2
Equilibrium: Reaction Quotient
Silver chloride will react with acetic acid to form the complex ion silver acetate. A reaction mixture is prepared by adding 0.25 g of AgCl to a 1.25 L solution that already contains 4.6×10‐6M Ag(CH3COO)(aq), 2.3×10‐3M Cl-, 1.1×10‐8M H+, and 0.010M CH3COOH. Based on this information, which of the statements below is true?
AgCl(s)+CH3COOH(aq)⇌Ag(CH3COO)(aq)+Cl−(aq)+H+(aq)K=5.87×10−16AgCl(s)+CH_3 COOH(aq)⇌Ag(CH_3 COO)(aq)+Cl^- (aq)+H^+ (aq)\qquad K = 5.87×10^{-16}
After allowing this solution to rest for some time:
Equilibrium: Reaction Quotient
Silver chloride will react with acetic acid to form the complex ion silver acetate. A reaction mixture is prepared by adding 0.25 g of AgCl to a 1.25 L solution that already contains 4.6×10‐6M Ag(CH3COO)(aq), 2.3×10‐3M Cl-, 1.1×10‐8M H+, and 0.010M CH3COOH. Based on this information, which of the statements below is true?
AgCl(s)+CH3COOH(aq)⇌Ag(CH3COO)(aq)+Cl−(aq)+H+(aq)K=5.87×10−16AgCl(s)+CH_3 COOH(aq)⇌Ag(CH_3 COO)(aq)+Cl^- (aq)+H^+ (aq)\qquad K = 5.87×10^{-16}
After allowing this solution to rest for some time:
Equilibrium
Consider the following equilibria:
2HCl(g)⇌H2(g)+Cl2(g)Kc,12HCl_{(g)} \rightleftharpoons H_{2(g)} +Cl_2{(g)} \hspace{20pt} K_c,1
2H2S2(g)⇌2H2(g)+S2(g)Kc,22H_2S_2{(g)} \rightleftharpoons 2H_{2(g)} +S_2{(g)} \hspace{20pt} K_c,2
Equilibrium
Consider the following equilibria:
2HCl(g)⇌H2(g)+Cl2(g)Kc,12HCl_{(g)} \rightleftharpoons H_{2(g)} +Cl_2{(g)} \hspace{20pt} K_c,1
2H2S2(g)⇌2H2(g)+S2(g)Kc,22H_2S_2{(g)} \rightleftharpoons 2H_{2(g)} +S_2{(g)} \hspace{20pt} K_c,2
Equilibrium
Consider the following equilibria:
2HCl(g)⇌H2(g)+Cl2(g)Kc,12HCl_{(g)} \rightleftharpoons H_{2(g)} +Cl_2{(g)} \hspace{20pt} K_c,1
2H2S2(g)⇌2H2(g)+S2(g)Kc,22H_2S_2{(g)} \rightleftharpoons 2H_{2(g)} +S_2{(g)} \hspace{20pt} K_c,2
Equilibrium
Consider the following equilibria:
2HCl(g)⇌H2(g)+Cl2(g)Kc,12HCl_{(g)} \rightleftharpoons H_{2(g)} +Cl_2{(g)} \hspace{20pt} K_c,1
2H2S2(g)⇌2H2(g)+S2(g)Kc,22H_2S_2{(g)} \rightleftharpoons 2H_{2(g)} +S_2{(g)} \hspace{20pt} K_c,2
Equilibrium
Consider the following equilibria:
2HCl(g)⇌H2(g)+Cl2(g)Kc,12HCl_{(g)} \rightleftharpoons H_{2(g)} +Cl_2{(g)} \hspace{20pt} K_c,1
2H2S2(g)⇌2H2(g)+S2(g)Kc,22H_2S_2{(g)} \rightleftharpoons 2H_{2(g)} +S_2{(g)} \hspace{20pt} K_c,2
Equilibrium
Consider the following equilibria:
2HCl(g)⇌H2(g)+Cl2(g)Kc,12HCl_{(g)} \rightleftharpoons H_{2(g)} +Cl_2{(g)} \hspace{20pt} K_c,1
2H2S2(g)⇌2H2(g)+S2(g)Kc,22H_2S_2{(g)} \rightleftharpoons 2H_{2(g)} +S_2{(g)} \hspace{20pt} K_c,2
Practice: Calculating Equilibrium Concentrations
Iodine chloride (ICl) can decompose, forming iodine and chlorine gases. If a reaction vessel is prepared by filling a 5.00 L container with 0.500 mol each of ICl, I2, and Cl2.
2ICl(g)⇌I2(g)+Cl2(g)KC=0.110 (at 25°C)2ICl(g)⇌I_2 (g)+Cl_2 (g)\qquad K_C = 0.110\ (at \ 25°C)
a) In which direction will the reaction proceed (towards products or reactants)? Show how you determined your answer.
Equilibrium constant
Which of the following is not included in an equilibrium equation?
Equilibrium constant
A 1.0 L flask was loaded and the system was allowed to reach equilibrium at 25 °C. The equilibrium mixture was found to contain: 1.5 mol Cr (S), 1.5 mol CCI4 (g), 2.3 mol CrCl3, (g), and 2.5 mol C (S). Determine the Kc value for this reaction at 25 °C.
4Cr(s)+3CCl4(g)⇌4CrCl3(g)+3C(s)ΔH=26.9kJ4Cr(s)+3CCl_4 (g)\rightleftharpoons4CrCl_3 (g)+3C(s)\qquad ΔH = 26.9 kJ
Equilibrium constant: Reaction quotient
Consider the reaction:
A+2B⇌C+DA + 2B ⇌ C + D
At a particular temperature this reaction is reactant-favoured at equilibrium. If for the current concentrations the forward reaction is favoured, which of the following statements is true?
Equilibrium: ICE table
Given the following reaction, if we start with 16moles of CH2=CHCH3(g), 16 moles of NH3(g) and 320moles of O2(g) in a 1L container, what will the equilibrium concentration be for H2O(g)?
CH2=CHCH3(g) + NH3(g) + 32O2(g) ⇌ CH2=CHC≡N(g) + 3H2O(g) K=1.2×1094
For this problem, since the K value is very large, the reaction will go to completion. We will have 1 ICE table for the reaction going to completion and a second ICE table for the reverse reaction where we will find the equilibrium concentrations!
ICE Tables
H2 and I2 are placed in a closed flask such that the concentrations of H2 and I2 are both 0.10 M respectively. The mixture is heated to 400oC and equilibrium is reached. Analysis of the equilibrium mixture finds HI to have a concentration of 0.050 M. Calculate the value of the equilibrium constant,
Kc. H2 (g) + I2 (g) ⇌ 2 HI (g)
Solution:
Concept Clarifier
Consider the following reaction
2 SO2+O2⇌2 SO3\rm 2\ {SO_2} \quad+\quad {O_2}\quad \xrightleftharpoons{\hspace{1.5cm}}\quad 2\ {SO_3}
ΔH0=−180 kJ/mol\Delta H^0=-180\ kJ/mol
Equilibrium constant: Kc
A one liter vessel was filled with 0.398 mol of NOCl(g). Then the temperature of the system was increased to 245 °C to undergo the following reaction:
2NOCl(g)⇌2NO(g)+Cl2(g)2NOCl(g) \rightleftharpoons 2NO(g) +Cl_2(g)
When equilibrium was attained, the concentration of Cl2 was 0.0225 mol/liter. Calculate the value of Kc at 245 °C for the reaction.
Equilibrium constant: Kc
A 1.0 L flask was loaded and the system was allowed to reach equilibrium at 25 °C. The equilibrium mixture was found to contain: 1.5 mol Cr (S), 1.5 mol CCI4 (g), 2.3 mol CrCl3, (g), and 2.5 mol C (S). Determine the Kc value for this reaction at 25 °C.
Equilibrium: ICE Table
Cyclohexane (C6H12) undergoes an isomerization in the presence of the appropriate catalyst to form a compound called MCP.
C6H12 (g) ⇌ MCP (g) Kc = 0.143 at 25oC
The initial concentrations are [C6H12] = 0.200 M and [MCP] = 0.100 M. What are the equilibrium concentrations of these two compounds?
Equilibrium: Magnitude of equilibrium constant
The value of Kc for a particular chemical equilibrium is 1.0x1013. Hence, we can conclude:
Equilibrium constant
Which of the following expression is the correct equilibrium-constant expression for the reaction below?
HF (aq) + H2O (l) ⇌ H3O+ (aq) + F- (aq)
Equilibrium Constant: Kp
Consider the following reaction:
N2O4 (g) ⇌ 2 NO2 (g)
A flask is charged with 6.000 atm of N2O4 (g) and 4.000 atm of NO2 (g) at 25oC. After equilibrium is reached the partial pressure of NO2 is 1.536 atm. Calculate Kp for the reaction.
Equilibrium: Concentration
An equilibrium mixture of CO, O2 and CO2 at a certain temperature contains [CO2] = 0.0010 M and [O2] = 0.0015 M. At this temperature the equilibrium constant Kc = 1.4x102.
2 CO (g) + O2 (g) ⇌ 2 CO2 (g) + heat
What is the equilibrium concentration of CO?
Equilibrium constant
Consider the following reaction of mercury and oxygen:
2 Hg (l) + O2 (g) ⇌ 2 HgO (s)
For this reaction, the equilibrium amounts of reactants and products are: 1.00 g of HgO (s), 2.00 mL of Hg (l), and 1.60 mol/L of O2 (g). What is the value of the equilibrium constant, Kc? (In case you wish to know, HgO (s) has molar mass 217 g/mol and density 1.10 g/mL, and metallic mercury Hg (l) has atomic mass 201 g/mol and density 13.6 g/mL.)
Equilibrium constant
What is the correct expression for the equilibrium constant of the following reaction? 6 CO2 (g) + 6 H2O (g) ⇌ C6H12O6 (s) + 6 O2 (g)
Equilibrium: ICE Table
A reaction mixture consisting of 0.400 mol H2 and 1.60 mol I2 was introduced into a 3.00 L flask and heated. At equilibrium 60% of the hydrogen gas had reacted. What is the equilibrium constant Kc for the reaction H2 (g) + I2 (g) ⇌ 2 HI (g)?
Equilibrium constant: Kp
Consider the equilibrium reaction: 2 NO2 (g) ⇌ N2O4 (g)
A container initially holds a mixture of 2.0 atm of N2O4 and 1.0 atm of NO2. The system is allowed to equilibrate and it is noticed that the pressure of NO2 has increased by 0.3 atm. What is the Kp for this equilibrium?
Equilibrium constant
Which of the following pairs of chemical equation and equilibrium constant expression is/are CORRECT?
1. 4 Bi (s) + 3 O2 (g) ⇌ 2 Bi2O3 (s), K = [O2]3
2. Ba (s) + 2 H+ (aq) ⇌ Ba2+ (aq) + H2 (g), K = [Ba2+][H2] / [H+]
Equilibrium: Equilibrium constant
For the process: PCl5 (g) ⇌ PCl3 (g) + Cl2 (g)
Kc = 0.040 at 450oC. If a reaction is initiated with 0.40 mol of Cl2 and 0.40 mol of PCl3 in a 1.0 liter container, what is the equilibrium concentration of Cl2 in the system?
Equilibrium: Equilibrium constant
For the process: N2 (g) + 3 H2 (g) ⇌ 2 NH3 (g)
Determine the value of Kc when an equilibrium mixture contains 0.0420 mol N2, 0.516 mol H2, and 0.0357 mol NH3 in a 1.00 liter container at 400oC.
Equilibrium: Equilibrium constant
For the process 2 SO3 (g) ⇌ 2 SO2 (g) + O2 (g), the equilibrium constant expression (Kc) is:
Equilibrium: Equilibrium constant
When 1.00 mol of H2 and 1.00 mol of Br2 are combined in a 1.00 liter flask and heated to 448oC, 0.780 mol of HBr are formed according to the equilibrium process H2 (g) + Br2 (g) ⇌ 2 HBr (g). What is Kc for this process at 448oC?
Equilibrium: Equilibrium Constant
Given the equilibrium information for water below, what is the concentration of hydroxide ions in a solution of 1.5 M HCl?
2 H2O (l) ⇌ H3O+ (aq) + OH- (aq), Kc = 1x10-14 at 20oC
Equilibrium: Equilibrium constant
Given the equilibrium information for water below, what is the concentration of hydroxide ions in water?
2 H2O (l) ⇌ H3O+ (aq) + OH- (aq), Kc = 1x10-14 at 20oC
Equilibrium: Equilibrium constant
For the equilibrium process NH4SH (s) ⇌ NH3 (g) + H2S (g), Kc = 1.2x10-4 at 218oC. What is the equilibrium concentration of NH3 if a sample of NH4SH is allowed to achieve equilibrium at 218oC in a sealed rigid vessel?
Equilibrium: Equilibrium constant
For the equilibrium process 2 NO (g) + Br2 (g) ⇌ 2 NOBr (g), the equilibrium constant expression (Kc) is:
Which equilibrium K expression for the reactions shown below is CORRECT?
For the equilibrium process 2 NO (g) + Br2 (g) ⇌ 2 NOBr (g), the equilibrium constant expression (Kc) is:
Equilibrium constant
The equilibrium constant for the process: AgCl (s) ⇌ Ag+ (aq) + Cl- (aq) is 1.0x10-10. What would be the equilibrium concentration of Ag+ in solution when 10 g of the AgCl salt is added to pure water?
Equilibrium constant
Equal quantities of hydrogen and gaseous iodine at 700 K (427oC) are placed in a reaction vessel and allowed to reach equilibrium according to the following equation:
H2 (g) + I2 (g) ⇌ 2 HI (g)
If the following equilibrium concentrations are measured: [H2] = [I2] = 0.021 mol/L and [HI] = 0.158 mol/L, what is the equilibrium constant for this reaction at 700 K?
Equilibrium: Equilibrium constant
If the equilibrium constant for reaction 1 below is K, what is the equilibrium constant for reaction 2?
(1) SO2 (g) + ½ O2 (g) ⇌ SO3 (g)
(2) 2SO3 (g) ⇌ 2 SO2 (g) + O2 (g)
Equilibrium: Equilibrium constant
If Kc = 0.212 at 100oC for N2O4 (g) ⇌ 2 NO2 (g)
Determine the value of Kc at 100oC for 2 NO2 (g) ⇌ N2O4 (g)
Equilibrium Constant
A 400 L reactor is charged with 10.0 moles of ammonia (NH3) at 450 K. Over time the ammonia decomposes into it's elements according to the reaction below and at equilibrium the pressure of H2 is 0.0140 atm. Calculate the equilibrium constant for this reaction.
2 NH3(g)→3 H2(g)+N2(g)2\ NH_{3(g)}\rightarrow 3\ H_{2(g)}+N_{2(g)}
Equilibrium constant
A reaction is shown below between chlorine gas and iodine gas at 600 K. After the reaction comes to equilibrium the partial pressures are
p(Cl2)=0.438 atm   p(I2)=0.146 atm    p(ICl3(g))=1.767 atmp(Cl_2)=0.438 \ atm\ \ \ p(I_2)=0.146\ atm \ \ \ \ p(ICl_{3(g)})=1.767\ atm
3 Cl2(g)+I2(g)→2 ICl3(g)3\ Cl_{2(g)}+I_{2(g)}\rightarrow 2\ ICl_{3(g)}
For an experiment involving the Haber’ process,
N2(g)+3H2(g)⇋2NH3(g)N_{2(g)}+3H_{2(g)} \leftrightharpoons 2NH_{3(g)}
The initial concentrations were: [N2] = 3.00 M, [H2] = 4.00 M and [NH3] = 1.00 M. After some time, the concentration of H2 was found to be 2.80 M. What was the concentration of NH3 at this time?
If an endothermic equilibrium reaction has a K value of 3.4 at room temperature, which of the following statements is correct?
Consider the following equilibrium:
Br2 (g) + Cl2 (g) ⇌ 2 BrCl (g) at 400 K, Kc = 7.0
If 0.20 M of Br2 (g) and 0.20 M of Cl2 (g) are placed in a vessel and heated to 400 K, what is the equilibrium concentrations of BrCl (g)?
At 450 K, the equilibrium constant in terms of pressure,
CO(g)+H2O(g)→H2(g)+CO2(g)Kp=34.7CH4(g)+O2→CO2(g)+2 H2(g)Kp=119.2\begin{array}{cc} CO_{(g)}+H_2O_{(g)}\rightarrow H_{2(g)}+CO_{2(g)} & K_p=34.7 \\ CH_{4(g)}+O_{2}\rightarrow CO_{2(g)}+2\ H_2{(g)} & K_p=119.2 \end{array}
What is Kp for the following reactio at 450 K?
The equilibrium constant, Kc, for the following reaction below was measured at 7.7.
SO3(g)+NO(g)⇌NO2(g)+SO2(g)SO_{3}(g)+NO(g)\rightleftharpoons NO_{2}(g)+SO_{2}(g)
At the same temperature the measurement was taken, a mixture of 0.4 M SO3 and 0.4 M NO was generated. After allowing the system to reach equilibrium what is the concentration of SO2?
Equilibrium constant
At a certain temperature, the value of the equilibrium constant for the following reaction is
Kc = 100. N2 (g) + 2 O2 (g) ⇌ 2 NO2 (g)
What is the equilibrium constant for the following reaction?
Equilibrium constant
Which of the following substances present in a chemical reaction would NOT normally be included in the equilibrium constant expression?
Equilibrium: ICE Table
Cyclohexane (C6H12) undergoes an isomerization in the presence of the appropriate catalyst to form a compound called MCP.
C6H12 (g) ⇌ MCP (g) Kc = 0.143 at 25oC
The initial concentrations are [C6H12] = 0.800 M and [MCP] = 0.100 M. What are the equilibrium concentrations of these two compounds?
Equilibrium: ICE Table
A mixture of 0.682 mol of H2 and 0.440 mol of Br2 combined in a reaction vessel with a volume of 2.00 L achieves equilibrium at 700 K according to the equation below. At equilibrium, there are 0.556 mol of H2 present. How many moles of Br2 are present at equilibrium?
H2 (g) + Br2 (g) ⇌ 2 HBr (g)
For a specific reaction, which of the following statements about the equilibrium constant is true?
Equilibrium: Equilibrium Constant
For the equilibrium process 2 SO3 (g) ⇌ 2 SO2 (g) + O2 (g), determine the value of Kc when an equilibrium mixture contains 0.025 mol O2, 0.27 mol SO2, and 0.018 mol SO3 in a 5.00 liter container at 220oC.
For the process: N2 (g) + 3 H2 (g) ⇌ 2 NH3 (g)
Determine the value of Kc when an equilibrium mixture contains 0.0420 mol N2, 0.516 mol H2, and 0.0357 mol NH3 in a 1.00 liter container at 400oC.
Which of the following expression is the correct equilibrium-constant expression for the reaction below?
HF(aq) + H2O(l) ⇌ H3O+(aq) + F-(aq)
1.
For the equilibrium process 2 NO (g) + Br2 (g) ⇌ 2 NOBr (g), the equilibrium constant expression (Kc) is:
Equilibrium Constant
A one liter vessel was filled with 0.398 mol of NOCl(g). Then the temperature of the system was increased to 245 °C to undergo the following reaction:
2NOCl(g)⇌2NO(g)+Cl2(g)2NOCl(g) \rightleftharpoons 2NO(g) +Cl_2(g)
When equilibrium was attained, the concentration of Cl2 was 0.0225 mol/liter. Calculate the value of Kc at 245 °C for the reaction.
Equilibrium
Consider the following equilibria:
2HCl(g)⇌H2(g)+Cl2(g)Kc,12HCl_{(g)} \rightleftharpoons H_{2(g)} +Cl_2{(g)} \hspace{20pt} K_c,1
2H2S2(g)⇌2H2(g)+S2(g)Kc,22H_2S_2{(g)} \rightleftharpoons 2H_{2(g)} +S_2{(g)} \hspace{20pt} K_c,2
Equilibrium: Equilibrium constant
For the equilibrium process NH4SH (s) ⇌ NH3 (g) + H2S (g), Kc = 1.2x10-4 at 218oC. What is the equilibrium concentration of NH3 if a sample of NH4SH is allowed to achieve equilibrium at 218oC in a sealed rigid vessel?
Equilibrium: Equilibrium Constant
For the equilibrium process 2 SO3 (g) ⇌ 2 SO2 (g) + O2 (g), determine the value of Kc when an equilibrium mixture contains 0.025 mol O2, 0.27 mol SO2, and 0.018 mol SO3 in a 5.00 liter container at 220oC.
Equilibrium constant
A 1.0 L flask was loaded and the system was allowed to reach equilibrium at 25 °C. The equilibrium mixture was found to contain: 1.5 mol Cr (S), 1.5 mol CCI4 (g), 2.3 mol CrCl3, (g), and 2.5 mol C (S). Determine the Kc value for this reaction at 25 °C.
Equilibrium: Magnitude of Equilibrium Constants
The value of KC for the reaction below is 1.2×10‐42 at 500 K.
H2(g)⇌2H(g)H_2 (g)⇌2H(g)
Which of the following statements is true when the reaction is at equilibrium?
Which answer below correctly describes the calculation to find the equilibrium expression K4?
CH4(g)+H2O(g)⇌CO(g)+3H2(g)K1CH4(g)+2S2(g)⇌CS2(g)+2H2S(g)K2CO2(g)+H2(g)⇌CO(g)+H2O(g)K3CS2(g)+2H2S(g)+3CO2(g)⇌4CO(g)+2S2(g)+2H2O(g)K4\def\arraystretch{1.5} \begin{array}{c:c} CH_4 (g)+H_2 O(g)⇌CO(g)+3H_2 (g) & K_1 \\ CH_4 (g)+2S_2 (g)⇌CS_2 (g)+2H_2 S(g) & K_2\\ CO_2 (g)+H_2 (g)⇌CO(g)+H_2 O(g) & K_3\\ CS_2 (g)+2H_2 S(g)+3CO_2 (g)⇌4CO(g)+2S_2 (g)+2H_2 O(g) & K_4 \end{array}
Equilibrium Constant
If 1.00 mole of HCl (g) is placed in an 8.00 L container, what will be the concentration of H2 in that container at equilibrium?
2HCl(g)⇌H2(g)+Cl2(g)KC=1.3×10−92HCl(g)⇌H_2 (g)+Cl_2 (g) \qquad K_C=1.3×10^{-9}
Equilibrium Constant
Carbon disulfide, CS2, and chlorine gas react according to the following equation:
CS2(g)+3Cl2(g)⇌S2Cl2(g)+CCl4(g)CS_2 (g)+3Cl_2 (g)⇌ S_2 Cl_2 (g)+CCl_4 (g)
When 1.00 mol of CS2 and 3.00 mol of Cl2 are placed in a 2.00 L container and allowed to come to equilibrium, the mixture is found to contain 0.250 mol of CCl4. What is the amount of Cl2 at equilibrium?
Equilibrium: Calculating Equilibrium Concentrations
Iodine chloride (ICl) can decompose, forming iodine and chlorine gases. If a reaction vessel is prepared by filling a 5.00 L container with 0.500 mol each of ICl, I2, and Cl2.
2ICl(g)⇌I2(g)+Cl2(g)KC=0.110 (at 25°C)2ICl(g)⇌I_2 (g)+Cl_2 (g)\qquad K_C = 0.110\ (at \ 25°C)
a) In which direction will the reaction proceed (towards products or reactants)? Show how you determined your answer.
Equilibrium Constant
Given the following information:
Ni(OH)2(s)⇌Ni2+(aq)+2OH−(aq)Ksp=6.0×10−16H2O(l)⇌H+(aq)+OH−(aq)Kw=1.0×10−14\def\arraystretch{1.5}\begin {array}{cc}Ni(OH)_2 (s) ⇌Ni^{2+} (aq)+2OH^- (aq)&&K_{sp}= 6.0 ×10^{-16}\\ H_2 O(l) ⇌H^+ (aq)+OH^- (aq) &&K_w= 1.0×10^{-14}\end{array}
What is the equilibrium constant for the reaction,
Equilibrium: Equilibrium constant
At 25 ˚C, KP = 5.2 × 10–2 for the following decomposition reaction:
NH4HS(s)⇌NH3(g)+H2S(g)NH_4HS(s)⇌NH_3(g)+H_2S(g)
Given the following information at 298 K:
SnO2(s)+2H2(g)⇌Sn(s)+2H2O(g)K1=8.12H2(g)+CO2(g)⇌H2O(g)+CO(g)K2=0.771\def\arraystretch{1.5} \begin{array}{cc} SnO_2 (s) + 2 H_2 (g) ⇌ Sn (s) + 2 H_2 O (g) & K_1 = 8.12 \\ H_2 (g) + CO_2 (g) ⇌ H_2 O (g) + CO (g) &K_2 = 0.771 \end{array}
Determine the K for the overall reaction: SnO2(s)+2CO(g)⇌Sn(s)+2CO2(g).SnO_2 (s) + 2 CO (g) ⇌ Sn (s) + 2 CO_2 (g).
Use the following information for both of the next two questions
We can easily observe shifts in the equilibrium of the following reaction because the reactants and products have different colours.
2NO2(g)⇌N2O4(g)Dark redColourless\def\arraystretch{1.5} \begin{array}{ccc} &2NO_2(g)&⇌&N_2O_4(g) \\ &\rm Dark \ red && \rm Colourless \end{array}
Chemical Equilibria
Consider this balanced chemical reaction and the molecular representation for both of the next two questions: 2AB(g)⇌A2(g)+B2(g)2AB(g)⇌A_2(g)+B_2(g)
The following equilibrium concentrations were observed in the synthesis of NH3 at
127oC:[NH3]=3.1×10−2M;[N2]=8.5×10−1M;[H2]=3.1×10−3M127^oC:[NH_3]=3.1\times 10^{-2} M; [N_2]=8.5\times 10^{-1} M; [H_2]=3.1\times 10^{-3}M
The balanced reaction is: N2 + 3H2 -eqm> NH3
Which of the graphs below could correctly illustrate the outcome of the reaction?
2BrCl⇌Cl2+Br22BrCl \rightleftharpoons Cl_2+Br_2 Kc=5.0K_c=5.0
Equilibrium: ICE Table
A sample of 0.0015 moles of F2 was sealed into a 1.0 L reaction vessel and heated to 1000. K to study the dissociation into F atoms:
F2⇌2F        Kc=1.2×10−4F_2 \rightleftharpoons 2F\ \ \ \ \ \ \ \ K_c=1.2\times 10^{-4}
What are [F2] and [F] at equilibrium?
Equilibrium: Reaction Quotient
Silver chloride will react with acetic acid to form the complex ion silver acetate. A reaction mixture is prepared by adding 0.25 g of AgCl to a 1.25 L solution that already contains 4.6×10‐6M Ag(CH3COO)(aq), 2.3×10‐3M Cl-, 1.1×10‐8M H+, and 0.010M CH3COOH. Based on this information, which of the statements below is true?
AgCl(s)+CH3COOH(aq)⇌Ag(CH3COO)(aq)+Cl−(aq)+H+(aq)K=5.87×10−16AgCl(s)+CH_3 COOH(aq)⇌Ag(CH_3 COO)(aq)+Cl^- (aq)+H^+ (aq)\qquad K = 5.87×10^{-16}
After allowing this solution to rest for some time:
The reaction for the reforming of methane from steam is given by:
CH4(g)+H2O(g)⇌CO(g)+3H2(g)CH_4(g)+H_2O(g)⇌CO(g)+3H_2(g)
A closed reaction vessel starts with initial concentrations of 1.00 M for every gas. After reaching equilibrium at a particular temperature, the final CO concentration was measured to be 0.80 M. Determine KC for this reaction at this temperature.