Aqueous Reactions and Solution Stoichiometry Mr. Kinton Honors Chemistry

Ionic Equations Complete Net Ionic Show all of the ions present in a chemical reaction Anything that is aqueous can be written as an ion Allows us to identify the driving force within a reaction Shows only the ions responsible for the reaction Will have 2 ions and either a (s), (l), or (g) product Spectator ions: Ions that do not participate in the reaction

Example

Example Write the complete ionic and net ionic equations for each of the following reactions: 3 (NH4)2CO3 (aq) + 2 Al(NO3)3 (aq) --> 6 NH4NO3 (aq) + Al2(CO3)3 (s)

Answer Complete Ionic Equation: 6 NH4+ (aq) + 3 CO32- (aq) + 2 Al3+ (aq) + 6 NO3- (aq)  6 NH4+ (aq) + 6 NO3- (aq) + Al2(CO3)3 (s) Net Ionic Equation: 2 Al3+ (aq) + 3 CO32- (aq)  Al2(CO3)3 (s)

Driving Forces Formation of a gas or precipitate Formation of a weak or nonelectrolyte Transfer of electrons during the reaction

Metathesis Reactions Reaction where positive and negative ions appear to change partners Precipitation reactions generally follow this pattern as well Examples- Pb(NO3)2(aq) + KI(aq)

Oxidation-Reduction Reactions Reaction where electrons are transferred between reactants Mainly in the form of single replacement reactions where a metal replaces another. Example- Aluminum with hydrobromic acid

Acid Base Reactions Neutralization reactions lead to the formation of a salt and water (weak or nonelectrolyte formed) With bases that do not contain hydroxide, gases are formed

Acids Substances that ionize to produce hydrogen ions (Arrhenius) Called proton donors (Bronsted-Lowry) Can also be an electron-pair acceptor (Lewis) Can donate many hydrogens depending on the acid Sour taste Turn litmus paper red Forms hydronium ion

Strength of Acids Strong Weak Only 7: HCl, HBr, HI, HClO3, HClO4, HNO3, and H2SO4 Strong electrolytes Every other acid is a weak acid Weak electrolytes Strong Weak

Bases Form hydroxide ions in solution (Arrhenius) Proton acceptor (Bronsted-Lowry) Electron pair donor (Lewis) Bitter taste Slippery feel Turn litmus paper blue Accept hydrogen ions

Strength of Bases Strong Weak Every other base is weak Weak electrolytes Only 8 Strong Bases: alkali and the bottom of the alkaline earth metal hydroxides Strong electrolytes Strong Weak

Autoionization of Water Water has the ability to act as an acid or base Occurs at chemical equilibrium Kw= [H+][OH-] = 1.0 x 10-14 at 25o C

pH Scale Molar concentration of H+ -log[H+] Acids: pH< 7.00 Bases: pH> 7.00 Neutral: pH =7.00

Calculate the pH of lemon juice, which has a concentration of [H+] of 3.8 x 10-4 Sig figs: based on the number of places after the decimal Calculating pH

Solution Stoichiometry We typically want to determine the number of moles of a substance Also useful in determining acid-base neutralizations

Examples How many grams of chloride ion are in a sample of water if 20.2 mL of .100 M Ag+ is needed to react with all the chloride? 45.7 mL of .500 M H2SO4 is required to neutralize a 20.0 mL sample of NaOH solution. What is the NaOH concentration?

Titrations Practical application for how to determine the concentration of a particular solute Combining a sample of known concentration (standard solution) Equivalence point: where the values are equivalent Indicator: used to determine the equivalence point Methyl Red- pH range of 4.2-6.3 Phenonlpthlaein- pH range of 8.3 to 10.0

Examples How many grams of Ca(OH)2 are needed to neutralize 25.0 mL of .100 M HNO3? How many liters of .500 M HCl are needed to completely react with .100 mol of Pb(NO3)2?