Chapter 7: Chemical reactions [Practice Classifying and Predicting Reactions]

1. Writing chemical equations
2. Balancing equations [Practice ]
3. Types of reactions: Combination
4. Types of reactions: Decomposition
5. Types of reactions: Single-replacement
6. Types of reactions: Double-replacement
7. Types of reactions: Combustion

7-1 Writing Chemical Equations [Practice Classifying and Predicting Reactions]

- Reactants (starting stuff)               > Products (ending stuff).

- Some symbols are used in writing reactions. See Chempire's Online Equation Symbol Guide.

7-2 Balancing Chemical Equations [Practice]

- Let's take this equation: H2 + O2         > H2O. This looks OK, but what happened to the second oxygen atom that was present on the left side? According to the Law of Conservation of Mass, everything that was there at the beginning must be there at the end. So we have to somehow show where it went. Like this: 2H2 + O2              > 2H2O. We say that we must start with 2 hydrogen diatoms and 1 oxygen diatom. Only then will both of the oxygen atoms get used up (to form 2 water molecules).

7-3 Combination Reactions [ Practice Classifying and Predicting Reactions]

- In a combination reaction, 2 or more substances combine to form 1 substance.

7-4 Decomposition Reactions [ Practice Classifying and Predicting Reactions]

- In a decomposition reaction, 1 substance breaks up into 2 or more substances.

7-5 Single Replacement Reactions [ Practice Classifying and Predicting Reactions]

- In a single replacement reaction, you must have a compound and a pure element. The atoms of the pure element replace one of the elements in the compound.

- The reaction will only happen if the pure element is more active than the one it is replacing. See Chempire's Online Activity Series of Metals to determine if this is true.

7-6 Double Replacement Reactions [ Practice Classifying and Predicting Reactions]

- Double replacement reactions are "criss-cross" reactions. The compounds switch cations. In other words: AB + CD          > AD + CB.

7-7 Combustion Reactions [ Practice Classifying and Predicting Reactions]

- In a combustion reaction oxygen reacts with a hydrocarbon (a compound made up of C and H) to form carbon dioxide and water.

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