Presentation on theme: "Compounds in Aqueous Solutions. Total Ionic Equations Once you write the molecular equation (synthesis, decomposition, etc.), you should check for reactants."— Presentation transcript:
Total Ionic Equations Once you write the molecular equation (synthesis, decomposition, etc.), you should check for reactants and products that are soluble or insoluble. We usually assume the reaction is in water We can use a solubility table to tell us what compounds dissolve in water. If the compound is soluble (does dissolve in water), then splits the compound into its component ions If the compound is insoluble (does NOT dissolve in water), then it remains as a compound
Total Ionic Equations Molecular Equation: K 2 CrO 4 + Pb(NO 3 ) 2 PbCrO 4 + 2 KNO 3 SolubleSolubleInsoluble Soluble Total Ionic Equation: 2 K + + CrO 4 -2 + Pb +2 + 2 NO 3 - PbCrO 4 (s) + 2 K + + 2 NO 3 -
Net Ionic Equations These are the same as total ionic equations, but you should cancel out ions that appear on BOTH sides of the equation Total Ionic Equation: 2 K + + CrO 4 -2 + Pb +2 + 2 NO 3 - PbCrO 4 (s) + 2 K + + 2 NO 3 - Net Ionic Equation: CrO 4 -2 + Pb +2 PbCrO 4 (s)
Net Ionic Equations Try this one! Write the molecular, total ionic, and net ionic equations for this reaction: Silver nitrate reacts with Lead (II) Chloride in hot water. AgNO 3 + PbCl 2 Molecular: 2 AgNO 3 + PbCl 2 2 AgCl + Pb(NO 3 ) 2 Total Ionic: 2 Ag + + 2 NO 3 - + Pb +2 + 2 Cl - 2 AgCl (s) + Pb +2 + 2 NO 3 - Net Ionic: Ag + + Cl - AgCl (s)
Ions are formed from solute molecules by the action of the solvent in a process called ionization. When a molecular compound dissolves and ionizes in a polar solvent, ions are formed where none existed in the undissolved compound. Hydrogen chloride, HCl, is a molecular compound that ionizes in aqueous solution. HCl contains a highly polar bond. Chapter 13 Ionization
The Hydronium Ion Some molecular compounds ionize in an aqueous solution to release H +. The H + ion attracts other molecules or ions so strongly that it does not normally exist alone. Chapter 13 The H 3 O + ion is known as the hydronium ion.
Strong and Weak Electrolytes Electrolytes are substances that yield ions and conduct an electric current in solution. The strength with which substances conduct an electric current is related to their ability to form ions in solution. Strong and weak electrolytes differ in the degree of ionization or dissociation. Chapter 13
Models for Strong and Weak Electrolytes and Nonelectrolytes
Strong Electrolytes A strong electrolyte is any compound whose dilute aqueous solutions conduct electricity well; this is due to the presence of all or almost all of the dissolved compound in the form of ions. To whatever extent they dissolve in water, they yield only ions. HCl, HBr, HI All soluble ionic compounds Chapter 13
[HF] >> [H + ] and [F – ] Weak Electrolytes A weak electrolyte is any compound whose dilute aqueous solutions conduct electricity poorly; this is due to the presence of a small amount of the dissolved compound in the form of ions. Some molecular compounds form aqueous solutions that contain not only dissolved ions but also some dissolved molecules that are not ionized. Chapter 13
Vapor Pressure Reduction Vapor Pressure of concentrated solution is lower because solute particles interfere with vaporization ΔT b = K b m Also results in boiling point elevation: Pure Solvent Solution
Solvent Particles travel from Right to Left Less concentrated to more concentrated
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