Decomposition and Redox

Decomposition and Redox: At the conclusion of our time together, you should be able to: 1.Identify decomposition chemical reactions 2.Show the change in oxidation numbers for this type of reaction

Decomposition Simple Reactions Synthesis (Combination) Single Replacement Double Replacement

Decomposition Synthesis Single Replacement Double Replacement ABAB + AB AB + ABAB + C + C ABAB + C + CDD

Decomposition Synthesis Single Replacement Double Replacement ABAB + AB AB + ABAB + C + C ABAB + C + CDD

2. Decomposition Reactions Decomposition reactions occur when a compound breaks up into the elements or in a few to simpler compounds Decomposition reactions occur when a compound breaks up into the elements or in a few to simpler compounds 1 Reactant  Product + Product 1 Reactant  Product + Product In general: AB  A + B In general: AB  A + B Example: 2 H 2 O  2H 2 + O 2 Example: 2 H 2 O  2H 2 + O 2 Example: 2 HgO  Example: 2 HgO  2Hg + O 2

2. Decomposition Reactions For Decomposition reactions to occur we need energy in the form of: For Decomposition reactions to occur we need energy in the form of: Heat Heat Light Light Electricity Electricity Mechanical Shock Mechanical Shock Or a Catalyst Or a Catalyst

Decomposition Reactions Another view of a decomposition reaction: Another view of a decomposition reaction:

Decomposition Exceptions Carbonates and chlorates are special case decomposition reactions that do not go to the elements. You should be able to recognize these as decomposition only. Carbonates and chlorates are special case decomposition reactions that do not go to the elements. You should be able to recognize these as decomposition only. Carbonates (CO 3 2- ) decompose to carbon dioxide and a metal oxide Carbonates (CO 3 2- ) decompose to carbon dioxide and a metal oxide Example: CaCO 3  CO 2 + CaO Example: CaCO 3  CO 2 + CaO Chlorates (ClO 3 - ) decompose to oxygen gas and a metal chloride Chlorates (ClO 3 - ) decompose to oxygen gas and a metal chloride Example: 2 Al(ClO 3 ) 3  2 AlCl O 2 Example: 2 Al(ClO 3 ) 3  2 AlCl O 2 There are other special cases, but we will not explore those in this class There are other special cases, but we will not explore those in this class

Practice Predict the products. Then, write and balance the following decomposition reaction equations: Predict the products. Then, write and balance the following decomposition reaction equations: Solid Lead (IV) oxide decomposes PbO 2(s)  Solid Lead (IV) oxide decomposes PbO 2(s)  Aluminum nitride decomposes Aluminum nitride decomposes AlN (s)  AlN (s)  Pb + O 2 Al + N 2

Practice of Decomposition and Redox Predict the products, balance the following reactions and show the change in oxidation numbers : Predict the products, balance the following reactions and show the change in oxidation numbers : H2OH2OH2OH2O H 2 + O 2 2 H 2 O  2 H 2 + O 2 Each H gains 1e - reduction, oxidizing agent Each O loses 2e - oxidation, reducing agent

Decomposition and Redox: Let’s see if you can: 1.Identify decomposition chemical reactions 2.Show the change in oxidation numbers for this type of reaction

Practice Identify the type of reaction for each of the following decomposition reactions, and write the balanced equation: BaCO 3(s)  NI 3(s)  BaO + CO 2 N 2 + I 2 2, 1, 3

Practice of Decomposition and Redox Predict the products, balance the following reactions and show the change in oxidation numbers : Predict the products, balance the following reactions and show the change in oxidation numbers : FeO  Fe + O 2 2 FeO  2 Fe + O 2 Each Fe(II) gains 2e - reduction, oxidizing agent Each O loses 2e - oxidation, reducing agent