Example Answers (on handout)

Soluble or Insoluble?

7. K3PO4 Soluble

8. Fe3(PO4)2 Insoluble

9. PbCl2 Insoluble (exception)

10. FeSO4 Soluble

11. (NH4)2S Soluble (exception)12. PbS Insoluble

•LAB THIS WEEK- ANALYSIS OF SILVER GROUP IONS

•OWL HOMEWORK- NEW ASSIGNMENTS POSTED

•ACID-BASE, SOLUBILITY, NET IONIC EQUATIONS

Announcements

Which of the following is soluble?

10%

29%

14%

47%

1 2 3 4

1. AlPO4

2. PbBr2

3. Al(OH)3

4. FeSO4

Which of the following is insoluble?

10%

61%

24%

5%

1 2 3 4

1. Al(NO3)3

2. PbC2O4

3. NaOH4. FeF3

pH Review

What is the pH of a 0.25M solution of NaOH? pH + pOH = 14 pOH=-log[OH-]

NaOH is a strong base [NaOH]=[OH-]

pOH= -log[0.25]=0.602

pH= 14 - pOH = 14 = 0.602 = 13.4

What is the [H3O+] of this solution?

[H3O+] = 10-pH = log-1(-pH)

[H3O+] = 10(-13.4) = 3.98 x 10-14M

Conjugate Acid-Base Pairs

Anions of weak acids are weak bases Conjugate acids and conjugate bases Example:

CH3COOH = weak acid

CH3COO- = weak base

What would this look like in a reaction?

CH3COONa + HCl ?

Anions of strong acids are neutral

Weak Acid Weak Base

CH3COOH CH3COO-

NH4+ NH3

H2CO3 CO32-

H2C2O4 C2O42-

H2SO3 SO32-

H2S S2-

H3PO4 PO43-

HCN CN-

HF F-

NHO2 NO2-

HClO ClO-

Conjugate Acids and Bases- More Examples

HCl + NaCN ?

HNO3 + AlPO4 ?

Net Ionic Equations

1. Write all reactants as they exist in solution2. Identify acids and bases

Need both acid and base present Look for “hidden bases” (anions of weak acids)

3. Ions that form insoluble compounds will form precipitates

4. Look for known gas-forming reactions5. Write out the products as they exist in

solution6. Cancel spectator ions

Precipitation ReactionsNet Ionic Equations

Pb(NO3)2 + K2CrO4 ?

Pb(NO3)2 + KI ?

Ba(NO3)2 + Na2C2O4 ?

Gas Forming Reactions

Special class of acid-base reactions

Combination of double displacement (swap) and decomposition reactions 2HCl + Na2CO3 ?

Gas Forming Reactions

2H+ + CO32- H2O(l) + CO2(g)

2H+ + S2- H2S(g)

2H+ + SO32- H2O(l) + SO2(g)

2H+ + M M2+ + H2(g)