CHM1045 Lecture 11 Outline of Last Lecture I Amount of Reactants and Products i Example 1 ii Example 2 II Limiting Reagent i Example 3 ii Example 4 III Reaction Yield i Example 5 Outline of Current Lecture IV Conduct electricity in solution V Ionization of acetic acid VI Precipitation Reactions VII Precipitation of Lead Iodide ii Example 1 I Writing net ionic equations iii Example 2 Current Lecture Chapter 4 Reactions in Aqueous Solutions A solution is a homogenous mixture of 2 or more substances The solute is are the substance s present in the smaller amount s The solvent is the substance present in the larger amount Solution Soft drink Air G Soft solder s Solvent H2O N2 Pb Solute Sugar CO2 O2 Ar CH4 Sn An electrolyte is a substance that when dissolved in water results in a solution that can conduct electricity A nonelectrolyte is a substance that when dissolved results in a solution that does not conduct electricity Conduct electricity in solution Cations and Anions Strong Electrolyte 100 dissociation NaCl s Na aq Cl aq Weak Electrolyte not completely dissociated CH3COOH CH3COO aq H aq Ionization of acetic acid CH3COOH CH3COO aq H aq A reversible reaction The reaction can occur in both directions Acetic acid is a weak electrolyte because its ionization in water is incomplete Hydration is the process in which an ion is surrounded by water molecules arranged in a specific manner Nonelectrolyte does not conduct electricity No cations and anions in solution C6H12O6 s H2O C6H12O6 aq Precipitation Reactions Precipitate insoluble solid that separates from solution Pb NO3 2 aq 2NaI aq PbI2 s 2NaNO3 aq molecular equation Pb2 2NO3 2Na 2I PbI2 s 2Na 2NO3 ionic equation 2 Pb 2I PbI2 s net ionic equation Na and NO3 are spectator ions Precipitation of Lead Iodide Pb2 2I PbI2 s Solubility is the maximum amount of solute that will dissolve in a given quantity of solvent at a specific temperature Example 1 Classify the following ionic compounds as soluble or insoluble a silver sulfate Ag2SO4 b calcium carbonate CaCO3 c sodium phosphate Na3PO4 a insoluble b insoluble c Na3PO4 Writing Net Ionic Equations 1 Write the balanced molecular equation 2 Write the ionic equation showing the strong electrolytes completely dissociated into cations and anions 3 Cancel the spectator ions on both sides of the ionic equation 4 Check that charges and number of atoms are balanced in the net ionic equation Example 2 Predict what happens when a potassium phosphate K3PO4 solution is mixed with a calcium nitrate Ca NO3 2 solution Write a net ionic equation for the reaction The balanced equation 2K3PO4 aq 3Ca NO3 2 aq Ca3 PO4 2 s 6KNO3 aq 6K aq 2PO3 4 aq 3Ca2 aq 6NO 3 aq 6K aq 6NO 3 aq Ca3 PO4 2 s Canceling the spectator ions K and NO 3 on each side of the equation we obtain the net ionic compound 3Ca2 aq 2PO3 4 aq Ca3 PO4 2 s
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