Steps to follow when writing your own equations

1. Word Problems: Predicting Products in Synthesis, Decomposition and Oxidation/Combustion reactions Given the beginning of a chemical reaction, how can you figure out what will be made, and if the reaction will actually happen?

2. Steps to follow when writing your own equations • Determine the type of reaction (Synthesis, Decomposition, Single Replacement, Double Replacement or combustion) • Use the reaction type information to predict the likely products • Synthesis • A + B  AB • N2 + 3H2  2NH3 • Elements combine to make a compound • Decomposition • AB  A + B • 6FeS 6Fe + S6 • A compound fall apart back into its ELEMENTS • We will always decompose compounds all the way back to the elements. • Oxidation/Combustion • AB + O2  AxOy + BxOy • 4FeS + 7O2  2Fe2O3 + 4SO2 • When the reactants involve carbon and hydrogen, CO2 and H2O will be your products

3. Steps to follow when writing your own equations – Continued Always check to make sure that you properly write each product making sure that the charges are balanced. Every compound must have zeronet charge. For Synthesis, Decomposition and combustion reactions you may assume that the reaction proceeds as written. Use coefficients to balance the equation.

4. Na2CO3 The problem tells you that it is a decomposition reaction ABC  A + B + C Use the elements as your products ____Na2CO3 ____Na + ____C + ____O2 Now, in this case oxygen is a very active product. It will attack both the sodium and carbon to produce a second reaction Na + C + O2  Na2O + CO2 So the real reaction in this case is… ____Na2CO3 ____Na2O + ____CO2 Example Problem 1 Sodium carbonate is decomposed by heating…

5. Al + O2 • Looks like a synthesis (two elements react) • A + B AB • It could also be called a combustion reaction too! • A + O2  AxOy • Al +O2 AlO • Remember that Al becomes an Al+3 ion and the oxygen ion is O-2 • Be sure that the charges in the product cancel out. • _____Al +______ O2 ______Al2O3 Example Problem 2 Aluminum strips and oxygen gas are allowed to react…

6. “Burned in air” is code for combustion or oxidation AB + O2 AO + BO C6H10O5 + O2  When C and H are reactants, CO2 and H2O are the products _____ C6H10O5 + ______ O2  ______ CO2 + _____ H2O Example Problem 3 Cellulose, C6H10O5, is burned in air…

7. Try these two problems on your own Practice Problem A • Isopropanol, C3H8O combusts in air… Practice Problem B • A chunk of lithium metal is left on a lab table exposed to the air… Pause the video and try these two problems on your own