1. General Properties of Aqueous Solution and Precipitation Reactions
Jing Gu

2. Concepts you will learn in this class
Solution
Solute
Solvent
Electrolyte:
-Strong electrolyte
-Weak electrolyte
-Non electrolyte
Precipitate
Solubility rules
Molecular equation and net ionic equations

3. Aqueous solution Universal solvent
Solution = homogenous mixture = solvent + solute
Solute = what is being dissolved( ≥ 1)
Solvent= what solute is dissolved into
Aqueous solution(aq) = H2O =Created by dissolving substances in water
Universal solvent

4. Electrolyte and nonelectrolyte
Electrolyte = dissociated in water to form ions
-Strong electrolyte = completely dissociate (NaCl, MgSO4, KI)
( Dissolve and Dissociate )
-Weak electrolyte= partially dissociate
-Non electrolyte = few ( or none) ions exists
In summary, for an electrolyte solution, the key to conduct electricity is to dissociated into its ionic form.

5. Hydration and Chemical equilibrium
Hydration, the process in which an ion is surrounded by water molecular arranged in a specific manner.
Chemical equilibrium ( Dissolve vs. Dissociate)
Dissolve and Dissociate
CH3 low case, half arrow or full arrow ?
Dissolve and Partially Dissociate
Equilibrium- nothing happens?
Equilibrium – reversible process
Only Dissolve

6. Questions
1. Which of the following diagrams best represents the hydration of NaCl when dissolved in water? The Cl- ion is larger in size than the Na+ ion.
2. Identify each of the following substances as a strong electrolyte, weak electrolyte, or nonelectrolyte: (a) KCl, (b) HNO3, (c) CH3COOH, (d) C12H22O11 (e) H2O,

7. Precipitate and solubility
Precipitate is formed when an insoluble compound is produced in a reaction.
If a compound is soluble in water (aq)
If it is insoluble, it will precipitate (s)
Or bubbles(g)
Metathesis or double-displacement reaction

8. Solubility Rules
For some compound’s solubility, it has no reason/ explanation as to why one compound is soluble in water and one compound is not. Thus, solubility “rules” were developed based on experience.
2 ways to use the rules:
To determine if a compound is soluble or insoluble
To determine when precipitation will form when two or more solvents are mixed together (determine the formula of the products, determine product phases(states)

9. Solubility Rules soluble insoluble soluble
Examples : Determine if K2S, CaSO4 and AgClO3 are soluble or not?
K2S K+, S2- (anything contains K+ is soluble, Li+, Na+, Rb+, Cs+)
CaSO4 Ca2+, SO42- (any sulfate of Ag+, Ca2+, Sr2+, Ba 2+, Hg22+, and Pb2+)
AgClO3 ( Any chlorates are soluble )
soluble
insoluble
Are a must for predicting if a precipitate might form in any given reaction
soluble

10. Solubility Rules
Examples : Determine two solvents are mixed, will the precipitate form?
(NH4)2CO3 (aq) + CaCl2( aq) ?
Are a must for predicting if a precipitate might form in any given reaction /Polyatomic ions
(NH4)2CO3 (aq) + CaCl2( aq) NH4Cl + CaCO3
(NH4)2CO3 (aq) + CaCl2( aq) NH4Cl(aq) + CaCO3 (s)

11. How to remember the solubility rules
Rule 1: Alkali metal ion are soluble
Are a must for predicting if a precipitate might form in any given reaction

12. How to remember the solubility rules
Are a must for predicting if a precipitate might form in any given reaction

13. How to remember the solubility rules
Rule 1. Alkali metal ion are soluble
Rule 2. Bicarbonate(HCO3-) , Ammonium ions( NH4+), Nitrates(NO3-), Chlorates (ClO3-), and Perchlorates(ClO4-) BANCh
Rule 3. Three Halides( Cl-, Br -, I-), except when they meet Ag+, Hg22+, Pb2+
Are a must for predicting if a precipitate might form in any given reaction

14. How to remember the solubility rules
Are a must for predicting if a precipitate might form in any given reaction

15. How to remember the solubility rules
Rule 1. Alkali metal ion are soluble
Rule 2. Bicarbonate(HCO3-) , Ammonium ions( NH4+), Nitrates(NO3-), Chlorates (ClO3-), and Perchlorates(ClO4-) BANCh
Rule 3. Three Halides( Cl-, Br -, I-), except when they meet Ag+, Hg22+, Pb2+
Rule 4. All the sulfates salts are soluable except Ag+, Hg22+, Pb2+, Ca2+, Sr2+, Ba2+
Are a must for predicting if a precipitate might form in any given reaction

16. How to remember the solubility rules
Are a must for predicting if a precipitate might form in any given reaction

17. How to remember the solubility rules
Rule 1. Alkali metal ion are soluble
Rule 2. Bicarbonate(HCO3-) , Ammonium ions( NH4+), Nitrates(NO3-), Chlorates (ClO3-), and Perchlorates(ClO4-) BANCh
Rule 3. Three Halides( Cl-, Br -, I-), except when they meet Ag+, Hg22+, Pb2+
All the sulfates salts are soluable except Ag+, Hg22+, Pb2+, Ca2+, Sr2+, Ba2+
Insoluble compound
Carbonate( CO32-), phosphates(PO43-), chromates( CrO42-), sulfides (S2-) and Hydroxides (OH-)
Except compounds containing alkali metal, Ammonium ions (NH4+) and the Ba2+ ion
Are a must for predicting if a precipitate might form in any given reaction

18. Molecular equation and ionic equation
Molecular equation: Formulas of the compounds are written as though all species existed as molecules or whole units. It is useful for reagents identification.
Pb2+(aq) + 2NO3-(aq) + 2K+(aq) +2I-(aq) PbI2(s) + 2K+(aq) +2NO3-(aq)
Ionic equation : what is really happened in the aqueous solution
Are a must for predicting if a precipitate might form in any given reaction
Pb2+(aq) + 2I-(aq) PbI2(s)
Net ionic equation : shows only the species that actually react in the reaction

19. Molecular equation and ionic equation
BaCl2(aq) + ZnSO4(aq)
A+B C+ D- ?
Step 1: Write a balance molecular equation based ABCD rule and solubility rule
BaCl2(aq) + ZnSO4(aq) BaSO4(s) + ZnCl2(aq)
Step 2: Split apart compounds from ions (determine changes) and write down all the ions in the solution.
Ba 2+, Cl-, Zn 2+, SO42-
Ba2+(aq) + 2Cl-(aq) + Zn2+ (aq)+ SO42-(aq) BaSO4(s) + Zn2+ +2Cl-
Step 3: Get rid of repeated ion at the reaction side and product side of equation
Ba2+(aq) + 2Cl-(aq) + Zn2+(aq) + SO42-(aq) BaSO4(s) + Zn2+(aq) +2Cl-(aq)
Step 4: Check the charges and number of atoms blance in the net ionic equation
Ba2+(aq) + SO42-(aq) BaSO4(s)
If chemistry is a language then molecular and ionic equations are the sentences of this lanuage.

20. Practice 1) Mg(NO3)2(aq) + 2NaOH(aq) 2) Na2S (aq) + ZnCl2 (aq)
Are a must for predicting if a precipitate might form in any given reaction

21. Practice 1) Mg(NO3)2(aq) + 2NaOH(aq) Mg(OH)2 (s) + 2NaNO3(aq)
Mg2+ (aq) + 2NO3- (aq) + 2Na+ (aq) + 2OH- (aq) Mg(OH)2(s) + 2NO3- (aq) + 2Na+ (aq)
Mg2+ (aq) + 2OH- (aq) Mg(OH)2(s)
2) Na2S (aq) + ZnCl2 (aq) ZnS(s) + 2NaCl(aq)
2Na+(aq) + S2-(aq) + Zn2+(aq)+2Cl-(aq) ZnS(s) + 2Na+(aq)+ 2Cl-(aq)
S2-(aq) + Zn2+(aq) ZnS(s)
Are a must for predicting if a precipitate might form in any given reaction

22. Overview Solution = homogenous mixture = solvent + solute
Solute = what is being dissolved( ≥ 1)
Solvent= what solute is dissolved into
Electrolyte:
-Strong electrolyte = completely dissociate (NaCl, MgSO4, KI)( Dissolve and Dissociate )
-Weak electrolyte= partially dissociate
-Non electrolyte = few ( or None) ions exists
Precipitate: is formed when an insoluble compound is produced in a reaction.
Solubility rules
Molecular equation and net ionic equations
Are a must for predicting if a precipitate might form in any given reaction