Chemical Equations and Reaction -

Chemical Equations

A chemical equation is a symbolic representation of a chemical reaction. It shows the reactants (starting materials) and products (substances formed) involved in a chemical reaction.

• Reactants: Substances that undergo the chemical change.

• Products: Substances formed as a result of the chemical change.

The general form of a chemical equation is:
\text{Reactants} \rightarrow \text{Products}

Types of Chemical Reactions

1. Combination Reaction: Two or more reactants combine to form a single product.

   • Example: A + B \rightarrow AB

2. Decomposition Reaction: A single compound breaks down into two or more simpler substances.

   • Example: AB \rightarrow A + B

3. Displacement Reaction: An element in a compound is replaced by another element.

   • Example: A + BC \rightarrow AC + B

4. Double Displacement Reaction: The ions of two compounds exchange places in an aqueous solution to form two new compounds.

   • Example: AB + CD \rightarrow AD + CB

5. Redox Reaction: A reaction involving the transfer of electrons between two species. Oxidation and reduction occur simultaneously.

   • Example: \text{Zn} + \text{Cu}^{2+} \rightarrow \text{Zn}^{2+} + \text{Cu}

Balancing Chemical Equations

To follow the law of conservation of mass, chemical equations must be balanced. This means that the number of atoms of each element must be the same on both sides of the equation.

Steps for Balancing Equations:

1. Write the unbalanced equation.

2. Count the number of atoms of each element in the reactants and products.

3. Use coefficients to balance the equation, updating the number of atoms as needed.

4. Check that the number of atoms is the same on both sides.

Importance of Chemical Reactions

• Chemical reactions are fundamental processes that enable changes in matter—from cooking food to industrial applications.

• Understanding these reactions helps in predicting outcomes of experiments and reactions in biological systems, pharmaceuticals, and manufacturing.