Transcript Lecture 8
Acids and Bases continued Which of the following is a strong acid? Hydrofluoric acid Chloric acid Sulfurous acid Hydrobromic acid Acetic acid 0 0% A ce t ic ac ac id id 0% id ro u s ac ac i ric hl o C yd ro b H yd ro f lu or ic ac 0 0% d id 10 0% ro m ic 0% H 130 Su lfu 1. 2. 3. 4. 5. GasForming Exchange Reaction Reaction of Metal Carbonates with Acids CaCO3(s) + 2CH3COOH(aq) Ca(CH3COO)2(aq) + H2CO3(aq) H2CO3(aq) H2O(l) + CO2(g) Carbonic acid is unstable and releases carbon dioxide gas Total Ionic Equation: CaCO3(s) + 2CH3COOH Ca2+ + 2CH3COO- + H2O + CO2(g) Net Ionic Equation is the same Reaction of Metal Sulfites and Sulfides with Acids CaSO3(s) + 2HCl(aq) CaCl2(aq) + H2SO3(aq) H2SO3(aq) H2O + SO2(g) Net Ionic Equation: CaSO3(s) + 2H+(aq) Ca2+(aq) + H2O(l) + SO2(g) Na2S(aq) + 2HCl(aq) 2NaCl(aq) + H2S(g) Net Ionic Equation: S2-(aq) + 2H+(aq) H2S(g) Which of the following is a gas forming reaction? Na2CO3+Ba(OH)2 AgNO3+Na2S ZnCO3+HNO3 HCl+CuSO4 1. 2. 3. 4. 130 10 0 0 Oxidation-Reduction Reactions Oxidation-Reduction Reactions Oxidation –loss of electrons Reduction – gain of electrons Oxidation and Reduction always occur together oxidizing agent – substance that causes oxidation reducing agent – substance that cause reduction Oxidation Is Loss Reduction Is Gain 4 e- Mn4+(O2-)2 Mn (s) + O2 (g) MnO2 (s) Manganese is oxidized Common Oxidizing and Reducing Agents Copper and Nitric Acid Nitric acid is a powerful oxidizing agent • The nitrogen in the nitric acid is reduced to NO2 (or sometimes NO) • 4HNO3(aq)+Cu(s) Cu(NO3)2(aq)+2NO2(g)+2H2O(l) -2 e- +2 e- Which species is the reducing agent in the Cu + HNO3 reaction? 1. 2. 3. 4. 5. 130 Cu NO2 Cu(NO3)2 HNO3 H2O 10 2O 0% H NO 3 0% H 3) 2 0% u( NO C N u C 0 0% O 2 0% 0 Copper Oxide and Hydrogen Gas 2Cu+O2 2CuO 2CuO+2H2 2Cu+2H2O Oxidation Numbers • To keep track of the movement of electrons in reactions we assign oxidation numbers to each element. Treat all interactions as ionic and assign electrons to the most electronegative element to give it its usual charge. • Sometimes real but usually not. Oxidation Number Rules • • • • • All pure elements have Ox# = 0 Monatomic ions have Ox# = charge Hydrogen is +1 unless with a metal then -1 Fluorine is -1 in all compounds Oxygen is -2 unless attached to fluorine or itself H-O-O-H both O’s are -1 • Other halogens are -1 unless attached to F or O Binary compounds • • • • CuCl2 Cu is +2, Cl is -1, the actual charges SCl2 Cl is assigned -1 Neutral compound so sum of ox# = 0 S + 2 × (-1) = 0, S is +2, assigned charge Finding Oxidation Numbers What is the oxidation number of S in H2SO4? • H +1 • O -2 • neutral compound, thus sum equals zero • 4O 4 -2 = -8 • 2H 2 +1 = +2 • 0 = +2 + S + (-8) S = +6 What is the oxidation number of N in HNO3? 1. 2. 3. 4. 5. 130 +7 +6 +5 +4 +3 10 0% 0% 3 0% 5 0% 6 0 7 0% 4 0 Oxidation State What is the oxidation state of Cr in Cr2O72-? • O -2 • ion, thus sum equals charge = -2 • 7O 7 -2 = -14 • -2 = 2 × Cr + (-14) • 2 × Cr = +12 • Cr = +6 What is the oxidation number of Br in BrF4+? 1. 2. 3. 4. 5. 130 +7 +6 +5 +4 +3 10 0% 0% 3 0% 5 0% 6 0 7 0% 4 0 Recognizing Redox Reactions Which of the following is a redox reaction? 1. 2. 3. 4. 5. CaCO3CaO+CO2(g) HNO3+KOHKNO3+H2O BaCl2+H2SO4BaSO4(s)+2HCl Ca+2H2OCa(OH)2+H2(g) Na2S+2HCl2NaCl+H2S(g) 130 10 0 0 Metal + Acid Displacement Activity Series of Metals Activity Series of Metals • metals higher in series react with compounds of those below • metals become less reactive to water top to bottom • metals become less able to displace H2 from acids top to bottom Potassium + Water Activity Series of Metals Zn(s) + CuSO4(aq) ZnSO4(aq) + Cu(s) Cu(s) + 2AgNO3(aq) Cu(NO3)2(aq) + 2Ag(s) Fe(s) + 2HCl(aq) FeCl2(aq) + H2(g) Zn(s) + 2HBr(aq) ZnBr2(aq) + H2(g) Metal + Metal Salt Displacement Which of the following reactions does NOT happen? Cu(s)+H2SO4(aq)CuSO4(aq)+H2(g) 2HNO3(aq)+2K(s)2KNO3(aq)+H2(g) FeCl2(aq)+Zn(s)ZnCl2(s)+Fe(s) Ca(s)+2H2O(l)Ca(OH)2(aq)+H2(g) Cu(s)+2AgNO3(aq)2Ag(s)+Cu(NO3)2(aq) 1. 2. 3. 4. 5. 130 10 0 0