General Properties of Aqueous Solution and Precipitation Reactions Jing Gu

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

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

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.

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

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,

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

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)

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

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) 2NH4Cl + CaCO3 (NH4)2CO3 (aq) + CaCl2( aq) 2NH4Cl(aq) + CaCO3 (s)

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

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

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

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

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 soluble except Ag+, Hg22+, Pb2+, Ca2+, Sr2+, Ba2+ Are a must for predicting if a precipitate might form in any given reaction

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

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

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

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.

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

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

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