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General Properties of Aqueous Solution and Precipitation Reactions Jing Gu.

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Presentation on theme: "General Properties of Aqueous Solution and Precipitation Reactions Jing Gu."— Presentation transcript:

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 Solution = homogenous mixture = solvent + solute Solute = what is being dissolved( ≥ 1) Solvent= what solute is dissolved into Aqueous solution(aq) = H 2 O =Created by dissolving substances in water Universal solvent

4 Electrolyte and nonelectrolyte Electrolyte = dissociated in water to form ions -Strong electrolyte = completely dissociate (NaCl, MgSO 4, 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 Dissolve and Partially Dissociate Only Dissolve Equilibrium- nothing happens? Equilibrium – reversible process

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) HNO 3, (c) CH 3 COOH, (d) C 12 H 22 O 11 (e) H 2 O,

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

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 Examples : Determine if K 2 S, CaSO 4 and AgClO 3 are soluble or not? K 2 S K +, S 2- (anything contains K + is soluble, Li +, Na +, Rb +, Cs + ) CaSO 4 Ca 2+, SO 4 2- (any sulfate of Ag +, Ca 2+, Sr 2+, Ba 2+, Hg 2 2+, and Pb 2+ ) AgClO 3 ( Any chlorates are soluble ) soluble insoluble soluble

10 Solubility Rules Examples : Determine two solvents are mixed, will the precipitate form? (NH 4 ) 2 CO 3 (aq) + CaCl 2 ( aq) ? (NH 4 ) 2 CO 3 (aq) + CaCl 2 ( aq) 2NH 4 Cl + CaCO 3 (NH 4 ) 2 CO 3 (aq) + CaCl 2 ( aq) 2NH 4 Cl(aq) + CaCO 3 (s)

11 How to remember the solubility rules Rule 1: Alkali metal ion are soluble

12 How to remember the solubility rules

13 Rule 1. Alkali metal ion are soluble Rule 2. Bicarbonate(HCO 3 - ), Ammonium ions( NH 4 + ), Nitrates(NO 3 - ), Chlorates (ClO 3 - ), and Perchlorates(ClO 4 - ) BANCh Rule 3. Three Halides( Cl -, Br -, I - ), except when they meet Ag +, Hg 2 2+, Pb 2+

14 How to remember the solubility rules

15 Rule 1. Alkali metal ion are soluble Rule 2. Bicarbonate(HCO 3 - ), Ammonium ions( NH 4 + ), Nitrates(NO 3 - ), Chlorates (ClO 3 - ), and Perchlorates(ClO 4 - ) BANCh Rule 3. Three Halides( Cl -, Br -, I - ), except when they meet Ag +, Hg 2 2+, Pb 2+ Rule 4. All the sulfates salts are soluable except Ag +, Hg 2 2+, Pb 2+, Ca 2+, Sr 2+, Ba 2+

16 How to remember the solubility rules

17 Rule 1. Alkali metal ion are soluble Rule 2. Bicarbonate(HCO 3 - ), Ammonium ions( NH 4 + ), Nitrates(NO 3 - ), Chlorates (ClO 3 - ), and Perchlorates(ClO 4 - ) BANCh Rule 3. Three Halides( Cl -, Br -, I - ), except when they meet Ag +, Hg 2 2+, Pb 2+ All the sulfates salts are soluable except Ag +, Hg 2 2+, Pb 2+, Ca 2+, Sr 2+, Ba 2+ Insoluble compound Carbonate( CO 3 2- ), phosphates(PO 4 3- ), chromates( CrO 4 2- ), sulfides (S 2- ) and Hydroxides (OH - ) Except compounds containing alkali metal, Ammonium ions (NH 4 + ) and the Ba 2+ ion

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. Pb 2+ (aq) + 2NO 3 - (aq) + 2K + (aq) +2I - (aq) PbI 2 (s) + 2K + (aq) +2NO 3 - (aq) Ionic equation : what is really happened in the aqueous solution Pb 2+ (aq) + 2I - (aq) PbI 2 (s) Net ionic equation : shows only the species that actually react in the reaction

19 Molecular equation and ionic equation BaCl 2 (aq) + ZnSO 4 (aq) A + B - + C + D - Step 1: Write a balance molecular equation based ABCD rule and solubility rule BaCl 2 (aq) + ZnSO 4 (aq) BaSO 4 (s) + ZnCl 2 (aq) Step 2: Split apart compounds from ions (determine changes) and write down all the ions in the solution. Ba 2+, Cl -, Zn 2+, SO 4 2- Ba 2+ (aq) + 2Cl - (aq) + Zn 2+ (aq)+ SO 4 2- (aq) BaSO 4 (s) + Zn 2+ +2Cl - Step 3: Get rid of repeated ion at the reaction side and product side of equation Ba 2+ (aq) + 2Cl - (aq) + Zn 2+ (aq) + SO 4 2- (aq) BaSO 4 (s) + Zn 2+ (aq) +2Cl - (aq) Step 4: Check the charges and number of atoms blance in the net ionic equation Ba 2+ (aq) + SO 4 2- (aq) BaSO 4 (s) ?

20 Practice 1) Mg(NO 3 ) 2 (aq) + 2NaOH(aq) 2) Na 2 S (aq) + ZnCl 2 (aq)

21 Practice 1) Mg(NO 3 ) 2 (aq) + 2NaOH(aq) Mg(OH) 2 (s) + 2NaNO 3 (aq) Mg 2+ (aq) + 2NO 3 - (aq) + 2Na + (aq) + 2OH - (aq) Mg(OH) 2 (s) + 2NO 3 - (aq) + 2Na + (aq) Mg 2+ (aq) + 2OH - (aq) Mg(OH) 2 (s) 2) Na 2 S (aq) + ZnCl 2 (aq) ZnS(s) + 2NaCl(aq) 2Na + (aq) + S 2- (aq) + Zn 2+ (aq)+2Cl - (aq) ZnS(s) + 2Na + (aq)+ 2Cl - (aq) S 2- (aq) + Zn 2+ (aq) ZnS(s)

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, MgSO 4, 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


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