Chapter 5- 2: Writing Chemical Equations

I. Understanding Chemical Equations

A. Chemical equations are a short way to writechemical reactions1. uses symbols instead of words.

Examples: 6CO2 + 6H2O C6H12O6 + 6O2

or 2H2 + O2 2H2O

B. Structure of an Equation

1. 2.

3. 4.

II. Conservation of Mass

A. mass of the reactants must equal mass of products.

1. beginning mass = ending mass

III. Classifying Chemical Reactions

A. Three (3) types of chemical reactions:

1. synthesis reactions2. decomposition reactions3. replacement reactions

1. Synthesis Reaction:a. reaction in which two or more substances

combine to form a single compound.

For example: Na +Cl NaCl

2. Decomposition reactiona. reaction in which a single compound breaks

down to form two ore more simpler substances.

For example: H2O2 H2O + O2

Water can be decomposed into the elements hydrogen and oxygen through electrolysis.

3. Single replacement reactiona. when one element replaces another in a

compound.Example: Zn +2HCl ZnCl2+ H2

Single replacement reaction:

4. Double replacement reaction a. reaction in which ions in two compounds switch places.Example: NaCl +AgF NaF +AgCl