1 of 25

Determination of the Equilibrium Constant

Alexander Calder

Maripose

1960

Contoso�Suites

2 of 25

Determination of the Equilibrium Constant

Equilibrium constants must be determined experimentally. The following practice problems show how this can be done.

Contoso�Suites

3 of 25

Determination of the Equilibrium Constant

RICE tables are about to become a big part of your life in equilibrium.

​

Reaction

Initial Concentrations

Change in Concentration

Equilibrium Concentrations

Contoso�Suites

4 of 25

Determination of the Equilibrium Constant

Example: Br2(g) + Cl2(g) ⇌ 2 BrCl(g)

0.60 mol of Br2 and 0.60 mol of Cl2 are placed in a 1.00 L flask and allowed to reach equilibrium. (There is no BrCl at first.) After reaching equilibrium, the flask is found to contain 0.28 mol of BrCl. What is the value of K for this reaction?

​

​

​

Set up RICE table. Be sure to use concentrations, not just moles.

 

Contoso�Suites

5 of 25

Determination of the Equilibrium Constant

Example: Br2(g) + Cl2(g) ⇌ 2 BrCl(g)

0.60 mol of Br2 and 0.60 mol of Cl2 are placed in a 1.00 L flask and allowed to reach equilibrium. (There is no BrCl at first.) After reaching equilibrium, the flask is found to contain 0.28 mol of BrCl. What is the value of K for this reaction?

​

R

​

​

​

​

​

I

​

​

​

​

​

C

​

​

​

​

​

E

​

​

​

​

​

Contoso�Suites

6 of 25

Determination of the Equilibrium Constant

Example: Br2(g) + Cl2(g) ⇌ 2 BrCl(g)

0.60 mol of Br2 and 0.60 mol of Cl2 are placed in a 1.00 L flask and allowed to reach equilibrium. (There is no BrCl at first.) After reaching equilibrium, the flask is found to contain 0.28 mol of BrCl. What is the value of K for this reaction?

​

R

Br2(g)

+

Cl2(g)

⇌

2 BrCl(g)

I

​

​

​

​

​

C

​

​

​

​

​

E

​

​

​

​

​

Contoso�Suites

7 of 25

Determination of the Equilibrium Constant

Example: Br2(g) + Cl2(g) ⇌ 2 BrCl(g)

0.60 mol of Br2 and 0.60 mol of Cl2 are placed in a 1.00 L flask and allowed to reach equilibrium. (There is no BrCl at first.) After reaching equilibrium, the flask is found to contain 0.28 mol of BrCl. What is the value of K for this reaction?

​

R

Br2(g)

+

Cl2(g)

⇌

2 BrCl(g)

I

0.60 M

​

0.60 M

​

0 M

C

​

​

​

​

​

E

​

​

​

​

​

Contoso�Suites

8 of 25

Determination of the Equilibrium Constant

Example: Br2(g) + Cl2(g) ⇌ 2 BrCl(g)

0.60 mol of Br2 and 0.60 mol of Cl2 are placed in a 1.00 L flask and allowed to reach equilibrium. (There is no BrCl at first.) After reaching equilibrium, the flask is found to contain 0.28 mol of BrCl. What is the value of K for this reaction?

​

R

Br2(g)

+

Cl2(g)

⇌

2 BrCl(g)

I

0.60 M

​

0.60 M

​

0 M

C

​

​

​

​

​

E

​

​

​

​

0.28 M

Contoso�Suites

9 of 25

Determination of the Equilibrium Constant

Example: Br2(g) + Cl2(g) ⇌ 2 BrCl(g)

0.60 mol of Br2 and 0.60 mol of Cl2 are placed in a 1.00 L flask and allowed to reach equilibrium. (There is no BrCl at first.) After reaching equilibrium, the flask is found to contain 0.28 mol of BrCl. What is the value of K for this reaction?

​

R

Br2(g)

+

Cl2(g)

⇌

2 BrCl(g)

I

0.60 M

​

0.60 M

​

0 M

C

- x

​

- x

​

​

E

​

​

​

​

0.28 M

Contoso�Suites

10 of 25

Determination of the Equilibrium Constant

Example: Br2(g) + Cl2(g) ⇌ 2 BrCl(g)

0.60 mol of Br2 and 0.60 mol of Cl2 are placed in a 1.00 L flask and allowed to reach equilibrium. (There is no BrCl at first.) After reaching equilibrium, the flask is found to contain 0.28 mol of BrCl. What is the value of K for this reaction?

​

2x = 0.28

x = 0.14

R

Br2(g)

+

Cl2(g)

⇌

2 BrCl(g)

I

0.60 M

​

0.60 M

​

0 M

C

- x

​

- x

​

+ 2x

E

​

​

​

​

0.28 M

Contoso�Suites

11 of 25

Determination of the Equilibrium Constant

Example: Br2(g) + Cl2(g) ⇌ 2 BrCl(g)

0.60 mol of Br2 and 0.60 mol of Cl2 are placed in a 1.00 L flask and allowed to reach equilibrium. (There is no BrCl at first.) After reaching equilibrium, the flask is found to contain 0.28 mol of BrCl. What is the value of K for this reaction?

​

R

Br2(g)

+

Cl2(g)

⇌

2 BrCl(g)

I

0.60 M

​

0.60 M

​

0 M

C

- 0.14 M

​

- 0.14 M

​

+ 0.28 M

E

​

​

​

​

0.28 M

2x = 0.28

x = 0.14

Contoso�Suites

12 of 25

Determination of the Equilibrium Constant

Example: Br2(g) + Cl2(g) ⇌ 2 BrCl(g)

0.60 mol of Br2 and 0.60 mol of Cl2 are placed in a 1.00 L flask and allowed to reach equilibrium. (There is no BrCl at first.) After reaching equilibrium, the flask is found to contain 0.28 mol of BrCl. What is the value of K for this reaction?

​

R

Br2(g)

+

Cl2(g)

⇌

2 BrCl(g)

I

0.60 M

​

0.60 M

​

0 M

C

- 0.14 M

​

- 0.14 M

​

+ 0.28 M

E

0.46 M

​

0.46 M

​

0.28 M

Contoso�Suites

13 of 25

Determination of the Equilibrium Constant

Example: Br2(g) + Cl2(g) ⇌ 2 BrCl(g)

0.60 mol of Br2 and 0.60 mol of Cl2 are placed in a 1.00 L flask and allowed to reach equilibrium. (There is no BrCl at first.) After reaching equilibrium, the flask is found to contain 0.28 mol of BrCl. What is the value of K for this reaction?

​

 

R

Br2(g)

+

Cl2(g)

⇌

2 BrCl(g)

I

0.60 M

​

0.60 M

​

0 M

C

- 0.14 M

​

- 0.14 M

​

+ 0.28 M

E

0.46 M

​

0.46 M

​

0.28 M

Contoso�Suites

14 of 25

Determination of the Equilibrium Constant

Example: Br2(g) + Cl2(g) ⇌ 2 BrCl(g)

0.60 mol of Br2 and 0.60 mol of Cl2 are placed in a 1.00 L flask and allowed to reach equilibrium. (There is no BrCl at first.) After reaching equilibrium, the flask is found to contain 0.28 mol of BrCl. What is the value of K for this reaction?

​

 

 

R

Br2(g)

+

Cl2(g)

⇌

2 BrCl(g)

I

0.60 M

​

0.60 M

​

0 M

C

- 0.14 M

​

- 0.14 M

​

+ 0.28 M

E

0.46 M

​

0.46 M

​

0.28 M

Contoso�Suites

15 of 25

Determination of the Equilibrium Constant

Example: Br2(g) + Cl2(g) ⇌ 2 BrCl(g)

0.60 mol of Br2 and 0.60 mol of Cl2 are placed in a 1.00 L flask and allowed to reach equilibrium. (There is no BrCl at first.) After reaching equilibrium, the flask is found to contain 0.28 mol of BrCl. What is the value of K for this reaction?

​

 

R

Br2(g)

+

Cl2(g)

⇌

2 BrCl(g)

I

0.60 M

​

0.60 M

​

0 M

C

- 0.14 M

​

- 0.14 M

​

+ 0.28 M

E

0.46 M

​

0.46 M

​

0.28 M

Contoso�Suites

16 of 25

Determination of the Equilibrium Constant

Example: 2 SO2(g) + O2(g) ⇌ 2 SO3(g)

1.00 mol of SO2 and 1.00 mol of O2 are placed in a 2.00-L flask at 1000 K. When equilibrium has been achieved, 0.925 mol of SO3 has formed. Calculate Kc, at 1000 K, for the reaction.

​

​

​

​

Set up RICE table. Be sure to use concentrations, not just moles.

 

Contoso�Suites

17 of 25

Determination of the Equilibrium Constant

Example: 2 SO2(g) + O2(g) ⇌ 2 SO3(g)

1.00 mol of SO2 and 1.00 mol of O2 are placed in a 2.00-L flask at 1000 K. When equilibrium has been achieved, 0.925 mol of SO3 has formed. Calculate Kc, at 1000 K, for the reaction.

​

R

2 SO2(g)

+

O2(g)

⇌

2 SO3(g)

I

​

​

​

​

​

C

​

​

​

​

​

E

​

​

​

​

​

Contoso�Suites

18 of 25

Determination of the Equilibrium Constant

Example: 2 SO2(g) + O2(g) ⇌ 2 SO3(g)

1.00 mol of SO2 and 1.00 mol of O2 are placed in a 2.00-L flask at 1000 K. When equilibrium has been achieved, 0.925 mol of SO3 has formed. Calculate Kc, at 1000 K, for the reaction.

​

R

2 SO2(g)

+

O2(g)

⇌

2 SO3(g)

I

0.500 M

​

0.500 M

​

0 M

C

​

​

​

​

​

E

​

​

​

​

​

Contoso�Suites

19 of 25

Determination of the Equilibrium Constant

Example: 2 SO2(g) + O2(g) ⇌ 2 SO3(g)

1.00 mol of SO2 and 1.00 mol of O2 are placed in a 2.00-L flask at 1000 K. When equilibrium has been achieved, 0.925 mol of SO3 has formed. Calculate Kc, at 1000 K, for the reaction.

​

R

2 SO2(g)

+

O2(g)

⇌

2 SO3(g)

I

0.500 M

​

0.500 M

​

0 M

C

​

​

​

​

​

E

​

​

​

​

0.4625 M

Contoso�Suites

20 of 25

Determination of the Equilibrium Constant

Example: 2 SO2(g) + O2(g) ⇌ 2 SO3(g)

1.00 mol of SO2 and 1.00 mol of O2 are placed in a 2.00-L flask at 1000 K. When equilibrium has been achieved, 0.925 mol of SO3 has formed. Calculate Kc, at 1000 K, for the reaction.

​

R

2 SO2(g)

+

O2(g)

⇌

2 SO3(g)

I

0.500 M

​

0.500 M

​

0 M

C

- 2x

​

- x

​

+ 2x

E

​

​

​

​

0.4625 M

Contoso�Suites

21 of 25

Determination of the Equilibrium Constant

Example: 2 SO2(g) + O2(g) ⇌ 2 SO3(g)

1.00 mol of SO2 and 1.00 mol of O2 are placed in a 2.00-L flask at 1000 K. When equilibrium has been achieved, 0.925 mol of SO3 has formed. Calculate Kc, at 1000 K, for the reaction.

​

R

2 SO2(g)

+

O2(g)

⇌

2 SO3(g)

I

0.500 M

​

0.500 M

​

0 M

C

- 0.4625 M

​

- 0.23125 M

​

+ 0.4625 M

E

​

​

​

​

0.4625 M

Contoso�Suites

22 of 25

Determination of the Equilibrium Constant

Example: 2 SO2(g) + O2(g) ⇌ 2 SO3(g)

1.00 mol of SO2 and 1.00 mol of O2 are placed in a 2.00-L flask at 1000 K. When equilibrium has been achieved, 0.925 mol of SO3 has formed. Calculate Kc, at 1000 K, for the reaction.

​

R

2 SO2(g)

+

O2(g)

⇌

2 SO3(g)

I

0.500 M

​

0.500 M

​

0 M

C

- 0.4625 M

​

- 0.23125 M

​

+ 0.4625 M

E

0.0375 M

​

0.26875 M

​

0.4625 M

Contoso�Suites

23 of 25

Determination of the Equilibrium Constant

Example: 2 SO2(g) + O2(g) ⇌ 2 SO3(g)

1.00 mol of SO2 and 1.00 mol of O2 are placed in a 2.00-L flask at 1000 K. When equilibrium has been achieved, 0.925 mol of SO3 has formed. Calculate Kc, at 1000 K, for the reaction.

​

 

R

2 SO2(g)

+

O2(g)

⇌

2 SO3(g)

I

0.500 M

​

0.500 M

​

0 M

C

- 0.4625 M

​

- 0.23125 M

​

+ 0.4625 M

E

0.0375 M

​

0.26875 M

​

0.4625 M

Contoso�Suites

24 of 25

Determination of the Equilibrium Constant

Example: 2 SO2(g) + O2(g) ⇌ 2 SO3(g)

1.00 mol of SO2 and 1.00 mol of O2 are placed in a 2.00-L flask at 1000 K. When equilibrium has been achieved, 0.925 mol of SO3 has formed. Calculate Kc, at 1000 K, for the reaction.

​

 

 

R

2 SO2(g)

+

O2(g)

⇌

2 SO3(g)

I

0.500 M

​

0.500 M

​

0 M

C

- 0.4625 M

​

- 0.23125 M

​

+ 0.4625 M

E

0.0375 M

​

0.26875 M

​

0.4625 M

Contoso�Suites

25 of 25

Determination of the Equilibrium Constant

Example: 2 SO2(g) + O2(g) ⇌ 2 SO3(g)

1.00 mol of SO2 and 1.00 mol of O2 are placed in a 2.00-L flask at 1000 K. When equilibrium has been achieved, 0.925 mol of SO3 has formed. Calculate Kc, at 1000 K, for the reaction.

​

 

Is this reaction product or reactant favored?

R

2 SO2(g)

+

O2(g)

⇌

2 SO3(g)

I

0.500 M

​

0.500 M

​

0 M

C

- 0.4625 M

​

- 0.23125 M

​

+ 0.4625 M

E

0.0375 M

​

0.26875 M

​

0.4625 M

Contoso�Suites