Aqueous Solutions & Solution Stoichiometry Basically chapter 4

Basic Definitions Solution – homogeneous mixture of 2+ substances Solvent – dissolving medium, usually present in the greatest quantity Aqueous solutions – solutions in which water is the solvent Solutes – other substances in the solution Electrolyte – substance whose aqueous solution contains ions

Strong Electrolytes Substances that exist in solution completely ionized. Includes most ionic compounds, strong acids, and strong bases Acids: H2SO4, HNO3, HClO4, HClO3, HCl, HBr, HI Only the 1st proton on H2SO4 completely ionizes Bases: Group 1 hydroxides, hydroxides of calcium, strontium, and barium Only the 1st OH- of the group 2 hydroxides completely ionizes

Weak Electrolytes Non-electrolytes Substances that exist in solution only partly ionized, such as weak acids and bases. Examples include acetic acid & ammonia Non-electrolytes Substances that do not form ions in solution Examples include sugars and alcohols

Practice Classify the following as strong, weak or non-electrolytes. Be able to explain your reasoning. Calcium chloride, CaCl2 Ammonium sulfate, (NH4)2SO4 Hydrocyanic acid, HCN Glucose, C6H12O6

Precipitation Reactions Precipitate – insoluble solid formed a reaction in solution Pb(NO3)2(aq) + 2NaBr(aq)  PbBr2(s) + 2NaNO3(aq) If the aqueous compounds are written as ions, spectator ions can be crossed out and the net ionic reaction can be written Pb+2 + 2NO3- + 2Na+ + 2Br-  PbBr2(s) + 2Na+ + 2NO3- Pb+2 + 2Br-  PbBr2(s)

Spectator Ions Spectator ions are ions that do not actually participate in the chemical reaction They progress from one side of the reaction to the other without undergoing any change

Predicting Precipitates Memorize solubility rules If a compound is insoluble or slightly soluble, it will be a precipitate Any compound that is soluble is aqueous

Writing Net Ionic Equations Write all the reactants that are indicated as solids, liquids, or gases. Re-write the formulas of aqueous compounds as ions. Predict and write the products. Balance the mass and charges using coefficients. Cross out spectator ions.

Practice Write the net ionic equations for each of the lab situations described below. Assume a reaction occurs in all cases. Aqueous solutions of silver nitrate and sodium phosphate are mixed. Aqueous copper(II) sulfate is added to solid sodium carbonate Hydrogen chloride gas is bubbled through an aqueous solution of lead(II) nitrate.

Aqueous solutions of silver nitrate and sodium phosphate are mixed.

Aqueous copper(II) sulfate is added to solid sodium carbonate

Hydrogen chloride gas is bubbled through an aqueous solution of lead(II) nitrate.