1. Keq for GASES Kp

2. Equilibrium and Pressure
2SO2(g) + O2(g) SO3(g)
If reactants and products are gases, partial pressures of each species can be used to determine the equilibrium
The total pressure = PSO2 + PO2+ PSO3

3. Concentration of Gases
For reactions that contain gases:
PV = nRT
P = (n/V)RT
P = CRT “C” is concentration in mol/L
C = P/RT
The concentration of a gas is directly proportional to the pressure exerted by the gas.

4. Problems Involving Pressure
2 NO2 (g) N2O4 (g) KP = 7.63atm at 300K. What are the equilibrium pressures of NO2 and N2O4 if a flask initially contains atm of NO2? What is the value of the Kc at 300K.

5. Relating Kp and Kc
Kp = Kc (RT)Δn Kp = partial pressure constant using atm Kc = molar concentration constant using M R = ideal gas constant, L-atm/mol-K T = absolute temperature in K Δn= moles of product – moles of reactants

6. DIFFERENT TYPE OF K

7. Ksp - Solubility Product of a Salt
KCl (s) K+ (aq) + Cl- (aq)
CaCl2 (s) Ca+2 (aq) Cl- (aq)

8. Ksp values Acid Formula Ka value Potassium nitrate KNO3 Very large
Calcium sulfate
CaSO4
3.0 x 10 -5
Lead (II) chloride
PbCl2
1.7 x 10 -5
Lead (II) iodide
PbI2
1.0 x 10 -8
Silver iodide
AgI
1.0 x
Silver sulfide
Ag2S
1.0 x
Is any substance truly insoluble?
Why are some substances more soluble than others?

9. Problem Involving Ksp
The Ksp of lead (II) chloride at 298K is 1.7 x 10-5.
Write the dissociation of lead (II) chloride in water.
Write the expression for the solubility product, Ksp, of lead (II) chloride.
Determine the concentration of the chloride ions and the lead ions of a saturated solution at 298K.

10. Kw - Autoionization of Water
Kw is 1.00 x at room temperature.
What would be the Keq expression?
How does the [H3O+] compare to the [OH-]?
What would be the [H3O+]?
What would be the pH?
Like any other equilibrium constant, the value of Kw varies with temperature.

11. Ka – Acid Dissociation Constant
Arrhenius acids dissociate to produce hydrogen ions in solution.
What is the difference between a strong and weak acid?

12. Ka values Acid Formula Ka value Perchloric acid HClO4 Very large
Hydrochloric acid
HCl
Nitric acid
HNO3
Sulfuric acid
H2SO4
Phosphoric acid
H3PO4
7.5 x 10 -3
Citric acid
H3C6H5O7
7.1 x 10 -4
Hydrofluoric acid HF
3.5 x 10 -4

13. Problem Involving Ka
Acetic acid, HC2H3O2, has a Ka of 1.7 x 10-5 at 298K.
Write the expression for the acid dissociation of acetic acid.
Determine the concentration of the hydrogen ions and the acetate ions at 298K of a 1.0 M acetic acid.

14. Kb – Base Dissociation Constant
Arrhenius bases dissociate to produce hydroxide ions in solution.
Some bases dissociate completely; other dissociate only partially. This determines if a base is strong or weak. 14

15. Kb values Based Formula Ka value Potassium hydroxide KOH Very large
Sodium hydroxide
NaOH
Zinc hydroxide
Zn(OH)2
9.6 x 10 -4
Methylamine
CH3NH2
3.7 x 10 -4
Ammonia
NH3
1.8 x 10 -5

16. Problem Involving Kb
1.0 moles of pure ammonia gas is dissolved to make a 1 Liter solution at 298K. Ammonia partially dissociates to produce the ions shown below. Ammonia, NH3, has a Kb of 1.8 x 10-5 at 298K.
Write the expression for the Kb of ammonia.
What is the hydroxide concentration at equilibrium?
What is the pH of a 1.0 M NH3(aq) solution? 16

17. DIFFERENT TYPE OF K
MULTISTEP REACTIONS 17

18. Overall Keq
A + B  C Keq = K1 C  D + E Keq = K2 A + B  D + E Keq = K1K2 18

19. Practice Problem Mg(OH)2 (s) Mg+2(aq) + 2 OH- (aq) Ksp = 5.6 x 10-11
MgF2 (s) Mg+2(aq) + 2 F- (aq) Ksp = 5.8 x 10-10
NET REACTION: 2 F- (aq) + Mg(OH)2 (s) OH- (aq) + MgF2 (s)
Manipulate the equations for the dissolving of Mg(OH)2 and MgF2 to obtain the net ionic reaction.
Calculate the Keq of the net ionic reaction. 19