2. 7.7 DECOMPOSITION REACTIONS By: Jason Kahan, Melissa Marini, and Jake Marrazzo

3. When a substance is heated it decomposes into two simpler compounds. Many compounds break apart or decompose with the addition of energy.

4.  A chemical decomposition reaction or analysis reaction is one of the most common types of chemical reactions

5. A WAY TO REMEMBER  Essentially, decomposition reactions are the opposite of combination reactions. A compound decomposes (i.e.,"splits-up") into two or more compounds and/or elements. For example mercury(II) oxide will, upon heating, decompose into mercury metal and oxygen:

6. In a decomposition reaction a single compound is broken down into two or more products. These products can be any combination of elements and compounds.

7. 3 RULES TO REMEMBER  1) All binary compounds will break down into their elements.  2) All carbonates break down to the oxide and carbon dioxide.  3. Chlorates (like KClO 3 and Ba(ClO 3 ) 2 )will break down to the binary salt and oxygen.

8. Examples of Decomposition: HgO ---> Hg + O 2 H 2 O ---> H 2 + O 2 FeS ---> Fe + S CaCO 3 ---> CaO + CO 2 Na 2 CO 3 ---> Na 2 O + CO 2

9. It is usually very difficult to predict the products of decomposition reactions. When a simple binary compound breaks down, however you know the products will be the constituent elements

10. A. Mg 2 +Cl 2 B. Mg+Cl C. Mg+Cl 2 D. M+G+C+L What would MgCl 2 break down into?

11. Most decomposition reactions require energy in the form of heat, light, or electricity. 2H 2 O( l ) electricity H 2 (g) + O 2 (g) What is the energy that causes the decomposition reaction in the problem above? A. heat B. Mr. sweeten C. fire D. Electricity

12. PRACTICE PROBLEMS Break down: 1. barium carbonate 2. magnesium carbonate 3. potassium chlorate

13. THE END