1. Chemical Equilibrium

4. Reversible Reactions
Both reactants and products exist together as a mixture
The ratio in which reactants and products are present in the mixture depends on the relative speeds of the forward and reverse reactions
Changing the rate of either the forward or the reverse reaction changes the ratio of products and reactants in the reaction mixture

5. Equilibrium Tank What is Equilibrium?
A chemical equilibrium exists when two opposing reactions occur simultaneously at the same rate, balancing each other

6. Equilibrium Concentrations
Product-favored Reaction

7. Equilibrium Concentrations
Reactant-favored Reaction

8. Reactants  Products
If a reaction is product-favored, the concentration of the products is higher than that of the reactants – the equilibrium is said to lie to the right
If a reaction is reactant-favored, the concentration of the reactants is higher than that of the products – the equilibrium is said to lie to the left
Arrows can be used to indicate the favorable direction

9. Equilibrium Constants
Equilibrium Constant: Keq
A + B C + D
𝐾 𝑒𝑞 = 𝐶 [𝐷] 𝐴 [𝐵]
aA + bB cC + dD
𝐾 𝑒𝑞 = [𝐶] 𝑐 [𝐷] 𝑑 [𝐴] 𝑎 [𝐵] 𝑏

10. Equilibrium Constant Rules
The concentrations of pure solids and liquids are not included in equilibrium constants
ALL gases and aqueous substances are included

11. ICE CHARTS Initial Concentration (M) Change in Concentration
Concentration at Equilibrium

12. ICE CHARTS
Example:  A mixture consisting initially of 3.00 moles NH3, 2.00 moles of N2, and 5.00 moles of H2, in a 5.00 L container was heated to 900 K, and allowed to reach equilibrium.  Determine the equilibrium concentration for each species present in the equilibrium mixture.
2 NH3(g)   N2(g) + 3 H2(g)    Kc = 900 K

13. ICE CHARTS NH3 N2 H2 Initial Concentration (M) Change in Conc. (M)
Example:  A mixture consisting initially of 3.00 moles NH3, 2.00 moles of N2, and 5.00 moles of H2, in a 5.00 L container was heated to 900 K, and allowed to reach equilibrium.  Determine the equilibrium concentration for each species present in the equilibrium mixture.
2 NH3(g)   N2(g) + 3 H2(g)    Kc = 900 K
NH3 N2 H2
Initial Concentration (M)
Change in Conc. (M)
Equilibrium Conc. (M)

14. ICE CHARTS NH3 N2 H2 Initial Concentration (M) 0.600 0.400 1.00
Example:  A mixture consisting initially of 3.00 moles NH3, 2.00 moles of N2, and 5.00 moles of H2, in a 5.00 L container was heated to 900 K, and allowed to reach equilibrium.  Determine the equilibrium concentration for each species present in the equilibrium mixture.
2 NH3(g)   N2(g) + 3 H2(g)    Kc = 900 K
NH3 N2 H2
Initial Concentration (M)
0.600
0.400
1.00
Change in Conc. (M)
Equilibrium Conc. (M)

15. ICE CHARTS NH3 N2 H2 Initial Concentration (M) 0.600 0.400 1.00
Example:  A mixture consisting initially of 3.00 moles NH3, 2.00 moles of N2, and 5.00 moles of H2, in a 5.00 L container was heated to 900 K, and allowed to reach equilibrium.  Determine the equilibrium concentration for each species present in the equilibrium mixture.
2 NH3(g)   N2(g) + 3 H2(g)    Kc = 900 K
NH3 N2 H2
Initial Concentration (M)
0.600
0.400
1.00
Change in Conc. (M)
+ 2 x
- x
- 3 x
Equilibrium Conc. (M)

16. ICE CHARTS NH3 N2 H2 Initial Concentration (M) 0.600 0.400 1.00
Example:  A mixture consisting initially of 3.00 moles NH3, 2.00 moles of N2, and 5.00 moles of H2, in a 5.00 L container was heated to 900 K, and allowed to reach equilibrium.  Determine the equilibrium concentration for each species present in the equilibrium mixture.
2 NH3(g)   N2(g) + 3 H2(g)    Kc = 900 K
NH3 N2 H2
Initial Concentration (M)
0.600
0.400
1.00
Change in Conc. (M)
+ 2 x
- x
- 3 x
Equilibrium Conc. (M) x x x

17. ICE CHARTS
Example: 4.00 moles of HI are placed in an evacuated 5.00 L flask and then heated to 800 K.  The system is allowed to reach equilibrium.  What will be the equilibrium concentration of each species
2 HI(g)    H2(g) + I2(g)     

18. ICE CHARTS HI(g) H2(g) I2(g) Initial Concentration (M)
Example: 4.00 moles of HI are placed in an evacuated 5.00 L flask and then heated to 800 K.  The system is allowed to reach equilibrium.  What will be the equilibrium concentration of each species
2 HI(g)    H2(g) + I2(g)     
HI(g)
H2(g)
I2(g)
Initial Concentration (M)
Change in Concentration (M)
Equilibrium Concentration (M)

19. ICE CHARTS HI(g) H2(g) I2(g) Initial Concentration (M) 0.800
Example: 4.00 moles of HI are placed in an evacuated 5.00 L flask and then heated to 800 K.  The system is allowed to reach equilibrium.  What will be the equilibrium concentration of each species
2 HI(g)    H2(g) + I2(g)     
HI(g)
H2(g)
I2(g)
Initial Concentration (M)
0.800
Change in Concentration (M)
Equilibrium Concentration (M)

20. ICE CHARTS HI(g) H2(g) I2(g) Initial Concentration (M) 0.800
Example: 4.00 moles of HI are placed in an evacuated 5.00 L flask and then heated to 800 K.  The system is allowed to reach equilibrium.  What will be the equilibrium concentration of each species
2 HI(g)    H2(g) + I2(g)     
HI(g)
H2(g)
I2(g)
Initial Concentration (M)
0.800
Change in Concentration (M)
- 2 x
+ x
Equilibrium Concentration (M)

21. ICE CHARTS HI(g) H2(g) I2(g) Initial Concentration (M) 0.800
Example: 4.00 moles of HI are placed in an evacuated 5.00 L flask and then heated to 800 K.  The system is allowed to reach equilibrium.  What will be the equilibrium concentration of each species
2 HI(g)    H2(g) + I2(g)     
HI(g)
H2(g)
I2(g)
Initial Concentration (M)
0.800
Change in Concentration (M)
- 2 x
+ x
Equilibrium Concentration (M) x
0 + x

22. ICE CHARTS
Example:  0.600 moles of NO and moles of O2 are placed in an empty 2.00 L flask.  The system is allowed to establish equilibrium.  What will be the equilibrium concentration of each species in the flask?
2 NO2(g)    2 NO(g) + O2(g)     Kc = 0.50

23. ICE CHARTS NO2(g) NO(g) O2(g) Initial Concentration (M)
Example:  0.600 moles of NO and moles of O2 are placed in an empty 2.00 L flask.  The system is allowed to establish equilibrium.  What will be the equilibrium concentration of each species in the flask?
2 NO2(g)    2 NO(g) + O2(g)     Kc = 0.50
NO2(g)
NO(g)
O2(g)
Initial Concentration (M)
Change in Concentration (M)
Equilibirum Concentration (M)

24. ICE CHARTS NO2(g) NO(g) O2(g) Initial Concentration (M) 0.300 0.375
Example:  0.600 moles of NO and moles of O2 are placed in an empty 2.00 L flask.  The system is allowed to establish equilibrium.  What will be the equilibrium concentration of each species in the flask?
2 NO2(g)    2 NO(g) + O2(g)     Kc = 0.50
NO2(g)
NO(g)
O2(g)
Initial Concentration (M)
0.300
0.375
Change in Concentration (M)
Equilibirum Concentration (M)

25. ICE CHARTS NO2(g) NO(g) O2(g) Initial Concentration (M) 0.300 0.375
Example:  0.600 moles of NO and moles of O2 are placed in an empty 2.00 L flask.  The system is allowed to establish equilibrium.  What will be the equilibrium concentration of each species in the flask?
2 NO2(g)    2 NO(g) + O2(g)     Kc = 0.50
NO2(g)
NO(g)
O2(g)
Initial Concentration (M)
0.300
0.375
Change in Concentration (M)
+ 2 x
- 2 x
- x
Equilibirum Concentration (M)

26. ICE CHARTS NO2(g) NO(g) O2(g) Initial Concentration (M) 0.300 0.375
Example:  0.600 moles of NO and moles of O2 are placed in an empty 2.00 L flask.  The system is allowed to establish equilibrium.  What will be the equilibrium concentration of each species in the flask?
2 NO2(g)    2 NO(g) + O2(g)     Kc = 0.50
NO2(g)
NO(g)
O2(g)
Initial Concentration (M)
0.300
0.375
Change in Concentration (M)
+ 2 x
- 2 x
- x
Equilibirum Concentration (M)
2 x x x