When reading Chapter 4: Skip p (Balancing Redox Equations/Redox Titrations)

Transcription

1 Announcements When reading Chapter 4: Skip p (Balancing Redox Equations/Redox Titrations) On to Chapter 5 today (Gases) Hour Exam 2 Aug 26 Goal is to cover up to and include Chapter Don t fall behind Please see me if you need help

2 There are 5-Main Types of Redox Reactions 1. Combination A + B => AB -produce fewer products than reactants. i. Element + Element => Compound ii. Element + Compound => New Compound iii. Compound + Compound => New Compound 2. Decomposition AB => A + B -produce more products than reactants. 3. Displacement AB + C => AC + B -methathesis (switching places) 4. Disproportionation--common element or element in compound is both oxidized and reduced 5. Combustion CO2 + O2 => CO2 + H2O

3 1. Combination Reactions: A + B => C Combination reactions produce fewer products than reactants. 1. Metal + Non-metal Binary Ionic Compound 2Na(s)+ Cl 2 2NaCl 2. Non-Metal + Non-metal Binary Molec Cmpd S + O 2 SO 2 3. Compound + Element New Compound +3 0 PCl3+ Cl 2 4. Compound + Compound New Compound CaO(s)+ H 2 O +5 PCl5 Ca(OH)2

4 2. Decomposition Reactions Decomposition reactions produce more products than reactants. 1. Compound Element A + Element B 2H2O 2H2 + O 2 2HgO 2Hg + O 2 2. Compound Compound A + Element B KClO 3 2KCl + 3O 2

5 3. Displacement Reactions More reactive metals will displace less reactive metals or hydrogen within their compounds to form the oxidized metal and the reduced form of the less active metal (or H2). A + BC AC + B Generalized Ca(s) + 2H 2 O(aq) Ca(OH) 2 + H 2 H2 Displacement Mg(s) + 2HCl(aq) MgCl 2 (aq) + H 2 (g) TiCl 4 + 2Mg Ti + 2MgCl 2 Zn(s) + CuSO4 => ZnSO4 + Cu (s) Metal Displacement

6 Activity Series For Metals Metals higher in the series will displace an element below it in the series from its aqueous compounds. H2 DISPLACEMENT Metals above H2 react with acids, or water to displace H2. H + reduced to H2. Al(s) + H + => Al 3+ + H2(g) Ag(s) + H + => No reaction METAL DISPLACEMENT More active metal + Salt of less active metal => Reduced Less active metal + Salt of more active metal. Al(s) + Fe 3+ => Al 3+ + Fe(s) Zn(s) + CuSO4 => ZnSO4 + Cu(s)

7 1. Fe(s) + 3Cu 2+ => 2Fe 3+ + Cu(s) 2. Sn(s) + Ca 2+ => Sn 2+ + Ca(s) 3. Au(s) + 3AgNO 3 (aq) => Au(NO 3 ) Ag(s) Predict whether the following reactions will occur as written Al(s) + Cr 2 O 3 (s) Al 2 O 3 (s) + 2 Cr(s) 5. Pt(s) + 4 HCl(aq) PtCl 4 (aq) + 2 H 2 (g)

8 A more active halogen will displace a less active (heavier) halide from their binary salts. F Cl2 + 2NaI ===> I2 + 2NaCl Br2 + 2NaI ===> I2 + 2NaBr I2(s) + 2F- ===> No reaction Strength as oxidizing agent Cl 2 Br 2 Cl2 and Br2 both are higher and will displace I - from its compounds, forming I2 and the chloride and bromide salt respectively. A less active halogen will not displace a more active halide from their salts. I 2 Halogen + Salt of Less Active Halide gives Less Active Halide + salt of more active halide.

9 Identifying the Type of Redox Reaction Classify each of the following redox reactions as a combination, decomposition, or displacement reaction, write a balanced molecular equation for each, as well as total and net ionic equations for part (c), and identify the oxidizing and reducing agents: (a) magnesium(s) + nitrogen(g) magnesium nitride (aq) (b) hydrogen peroxide(l) water(l) + oxygen gas (c) aluminum(s) + lead(ii) nitrate(aq) aluminum nitrate(aq) + lead(s) Combination reactions produce fewer products than reactants. Decomposition reactions produce more products than reactants. Displacement reactions have the same number of products and reactants.

10 Identifying the Type of Redox Reaction Mg(s) + N 2 (g) Mg 3 N 2 (aq) H 2 O 2 (l) H 2 O(l) + 1/2 O 2 (g) or (a) Combination Mg is the reducing agent; N 2 is the oxidizing agent. 2 H 2 O 2 (l) 2 H 2 O(l) + O 2 (g) H 2 O 2 is the oxidizing and reducing agent. (b)decomposition (c)displacement Al(s) + Pb(NO 3 ) 2( aq) Al(NO 3 ) 3 (aq) + Pb(s) 2Al(s) + 3Pb(NO 3 ) 2( aq) 2Al(NO 3 ) 3 (aq) + 3Pb(s) Pb(NO 3 ) 2 is the oxidizing and Al is the reducing agent.

11 4. Disproportionation Reaction A single element in a compound is both oxidized and reduced (both oxidizing and reducing agent in one) H2O2 + 2OH - 2H 2 O + O Cl 2 + 2OH - ClO - + Cl - + H 2 O

12 5. Combustion Reaction In a combustion reaction a fuel or typically a hydrocarbon reacts with oxygen forming carbon dioxide and water. The oxygen is increases in O.N. and is therefore oxidized (reducing agent) CH4 + 2O2 CO2 + 2H 2 O 2C4H O2 8CO2 + 10H 2 O

13 Burning organic compounds containing sulfur gives sulfur dioxide (SO2) and leads to acid rain production. 2C2H5SH(coal) + 9O2(g) => 4CO 2 (g) + 6H 2 O + 2SO2(g) 2SO2(g) + O2(g) => 2SO3(g) SO3(g) + H2O(g) => H2SO4(aq)

14 Quiz 3 MnO Fe H + - Mn Fe H2O The oxidizing agent in the above reaction is? The reducing agent is? Right the oxidation number for every atom in the equation shown above. The species that is oxidized is? The species that is reduced is?