Writing and Balancing Chemical Equations

Study Notes

CHEMICAL EQUATION

A chemical equation represents the substances involved in a chemical reaction.
Reactants are on the left side, products on the right.
Example format: Reactants → Products.

Writing a Chemical Equation

Identify reactants and products of the reaction.
Use correct chemical symbols and formulas.
Follow the law of conservation of mass, ensuring the same number of each type of atom on both sides.

Balanced Chemical Equations

A balanced equation has equal numbers of each type of atom on both sides.
To balance:
- Adjust coefficients (numbers in front of formulas), not subscripts.
- Start with the most complex molecule or the one with the most different elements.
- Balance elements one at a time, checking after each adjustment.
Example:
- Unbalanced: H₂ + O₂ → H₂O
- Balanced: 2 H₂ + O₂ → 2 H₂O

TYPES OF CHEMICAL REACTION

Synthesis Reaction
- Two or more reactants combine to form a single product.
- General form: A + B → AB
Decomposition Reaction
- A single compound breaks down into two or more simpler substances.
- General form: AB → A + B
Single Replacement Reaction
- One element replaces another in a compound.
- General form: A + BC → AC + B
Double Replacement Reaction
- Exchange of ions between two compounds to form two new compounds.
- General form: AB + CD → AD + CB
Combustion Reaction
- A substance combines with oxygen, releasing energy (heat/light).
- Typically involves hydrocarbons reacting with oxygen producing CO₂ and H₂O.
- General form: CₓHᵧ + O₂ → CO₂ + H₂O
Redox Reaction
- Involves the transfer of electrons, changing the oxidation states of elements.
- Composed of oxidation (loss of electrons) and reduction (gain of electrons) processes.

Chemical Equation

Represents substances involved in a chemical reaction.
Reactants are situated on the left side, while products are on the right.
Standard notation: Reactants → Products.

Writing a Chemical Equation

Begin by identifying the reactants and products.
Employ correct chemical symbols and formulas.
Adhere to the law of conservation of mass, ensuring equal atom counts for each type on both sides.

Balanced Chemical Equations

A balanced equation features equal quantities of each atom on both sides.
Balance by adjusting coefficients (whole numbers in front of formulas), Keeping subscripts unchanged.
Start with the most complex molecule or the molecule with the greatest number of different elements.
Balance elements individually and check the equation after each modification.
Example of balancing:
- Unbalanced: H₂ + O₂ → H₂O
- Balanced: 2 H₂ + O₂ → 2 H₂O.

Types of Chemical Reactions

Synthesis Reaction
- Two or more reactants combine to produce a single product.
- General form: A + B → AB.
Decomposition Reaction
- A singular compound disassembles into two or more simpler substances.
- General form: AB → A + B.
Single Replacement Reaction
- An element substitutes for another within a compound.
- General form: A + BC → AC + B.
Double Replacement Reaction
- Involves an exchange of ions between two compounds, forming two new compounds.
- General form: AB + CD → AD + CB.
Combustion Reaction
- Involves a substance reacting with oxygen, releasing energy in the form of heat or light.
- Typically includes hydrocarbons reacting with oxygen, yielding carbon dioxide (CO₂) and water (H₂O).
- General form: CₓHᵧ + O₂ → CO₂ + H₂O.
Redox Reaction
- Entails electron transfer, resulting in changes in the oxidation states of elements.
- Composed of oxidation (loss of electrons) and reduction (gain of electrons) processes.

Description

This quiz explores the fundamentals of writing and balancing chemical equations. Learn to identify reactants and products, and understand how to apply the law of conservation of mass in reactions. You will also discover various types of chemical reactions, including synthesis reactions.