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Types of Reactions precipitate: a solid product that forms in an aqueous solution reaction Na2CO3 (aq) + Ca(NO3)2 (aq) CaCO3(s) + ppt clear Na2CO3 solution clear Ca(NO3)2 solution 2 NaNO3 (aq) “chunks” “sinkies” “floaties” cloudy solution containing CaCO3(s) and NaNO3(aq) Key Terms Term Definition soluble able to be dissolved insoluble does not dissolve in solution (or water) an insoluble solid formed precipitate when two solutions are mixed In an Equation (aq) (ins) (s) Using Solubility Rules – Most solubility rules are written based on the negative ion or anion • Soluble compounds contain… Insoluble compounds contain… For these compounds, common exceptions are INSOLUBLE. For these compounds, common exceptions are SOLUBLE. How to Determine if a Compound is Soluble or Insoluble? • Find the anion in the compound. • Find the rule in the solubility tables that matches the ion. • Double check to make sure the cation isn’t listed as an exception. Predict if the following compounds are soluble or insoluble. – CaCl2 Soluble – CuSO4 Soluble – Al2(CrO4)3 Insoluble – Mg(OH)2 Insoluble Insoluble – AgCl – SrS Soluble Predicting if a Precipitate will Form –Precipitate reactions are precipitation reactions. –In order for a reaction to be a precipitation reaction, there must be • one solid product, which is the precipitate, and • both reactants should be aqueous solutions Determine which reactions are precipitation reactions or reactions that will form a precipitate. • Pb(NO3)2 + KI (aq) (aq) PbI2 (s) + KNO3 (aq) • (NH4)2CO3 + K2S K2CO3 + (NH4)2S (aq) (aq) (aq) (aq) • Ag + Cu(NO3)2 (s) (aq) • Ba(OH)2 (aq) AgNO3 + Fe(ClO4)3 (aq) NO + Cu (aq) NO (s) Ba(ClO4)2 + Fe(OH)3 (aq) YES YES (s) Neutralization Reaction • A reaction between and acid and a base which results in the production of a salt and water. ACID + BASE = SALT + WATER HCl(aq) + NaOH(aq) = H2O(l) + NaCl(aq) Mg(OH)2(s) + 2HCl(aq) = MgCl2(aq) + 2H2O(l) 9 Reduction-Oxidation Reaction REDOX • A reaction in which electrons are transferred from one species to another. • Oxidation means the loss of electrons. • Reduction means the gain of electrons. LEO says GER Loss Electrons = Oxidation Gain Electrons = Reduction Many oxidation-reduction reactions are single replacement reactions Oxidation Reduction Reactions (Redox) 0 1 0 1 2 Na Cl 2 2 Na Cl Each sodium atom loses one electron: 1 0 Na Na e Each chlorine atom gains one electron: 0 1 Cl e Cl LEO says GER : Lose Electrons = Oxidation 1 0 Na Na e Sodium is oxidized Gain Electrons = Reduction 0 1 Cl e Cl Chlorine is reduced Rules for Assigning Oxidation Numbers Rules 1 & 2 1. The oxidation number of any uncombined element is zero 2. The oxidation number of a monatomic ion equals its charge 0 0 1 1 2 Na Cl 2 2 Na Cl Rules for Assigning Oxidation Numbers Rules 3 & 4 3. The oxidation number of oxygen in compounds is -2 4. The oxidation number of hydrogen in compounds is +1 1 2 H2O Rules for Assigning Oxidation Number Rule 5 5. The sum of the oxidation numbers in the formula of a compound is 0 1 2 H2O 2(+1) + (-2) = 0 H O 2 2 1 Ca(O H ) 2 (+2) + 2(-2) + 2(+1) = 0 Ca O H Rules for Assigning Oxidation Numbers Rule 6 6. The sum of the oxidation numbers in the formula of a polyatomic ion is equal to its charge ? 2 N O3 X + 3(-2) = -1 N O X = +5 ? 2 S O4 X + 4(-2) = -2 S O X = +6 2 Assigning Oxidation States Example: Assign oxidation states to all atoms in the following. a. CO2 O = -2 (for each oxygen); C = +4 b. SF6 F = -1 (for each fluorine); S = +6 c. NO3- O = -2 (each oxygen); N = +5 d. MnO4- O = -2 (each oxygen); Mn = +7 e. HSO3- O = -2 (each oxygen); H = +1, S = +4 f. H2O H = +1 (each); O = -2 g. Li3N Li = +1 (each); N = -3