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 zero net charge. For Synthesis, Decomposition and combustion reactions you may assume that the reaction proceeds as written. Use coefficients to balance the equation.

4. Sodium carbonate is decomposed by heating…
Example Problem 1
Sodium carbonate is decomposed by heating…
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

5. Aluminum strips and oxygen gas are allowed to react…
Example Problem 2
Aluminum strips and oxygen gas are allowed to react…
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
(Given more time, we could figure out which compound is actually created by doing some stoichiometry and/or looking at the color of the solution formed.)

6. Cellulose, C6H10O5, is burned in air…
Example Problem 3
Cellulose, C6H10O5, is burned in air…
“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
(Given more time, we could figure out which compound is actually created by doing some stoichiometry and/or looking at the color of the solution formed.)

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