Classroom Central

A Chemical Equation is a concise way of representing a chemical reaction using chemical symbols and formulas. It shows the original substances (reactants) transforming into new substances (products). The most important rule is the Law of Conservation of Mass, which states that the total number of atoms of each element must be the same before and after the reaction (the equation must be balanced).

Key Points and Definitions

a. Reactants: The starting substances in a reaction. They are always written on the left side of the arrow.
b. Products: The new substances formed in the reaction. They are always written on the right side of the arrow.
c. The Arrow ( $⟶$ ): Means "yields," "produces," or "forms." It separates the reactants from the products.
d. Coefficient: The large whole number written in front of a chemical formula (e.g., the '2' in $2 H_{2}$ ). This number is used to balance the equation.
e. Balancing: The process of ensuring the number of atoms of every element is equal on both sides of the equation.

Important Examples

Here are three simple and fundamental chemical equations:

1. Formation of Water (Synthesis)

This shows two elements, Hydrogen ( $H_{2}$ ) and Oxygen ( $O_{2}$ ), combining to form the compound Water ( $H_{2} O$ ).

Equation: 2 H_{2} + O_{2} ⟶ 2 H_{2} O

Explanation: Two molecules of hydrogen react with one molecule of oxygen to produce two molecules of water.

2. Rusting of Iron (Oxidation)

This slow reaction involves Iron ( $Fe$ ) reacting with Oxygen ( $O_{2}$ ) to form Iron(III) oxide ( $Fe_{2} O_{3}$ ), which is commonly known as rust.

Equation: 4 Fe + 3 O_{2} ⟶ 2 Fe_{2} O_{3}

Explanation: Four atoms of iron react with three molecules of oxygen to produce two units of rust.

3. Neutralization Reaction

This is a reaction between an acid (like Hydrochloric Acid, $HCl$ ) and a base (like Sodium Hydroxide, $NaOH$ ) to produce a salt (Sodium Chloride, $NaCl$ ) and water.

Equation: HCl + NaOH ⟶ NaCl + H_{2} O

Explanation: One molecule of acid reacts with one molecule of base to produce one molecule of salt and one molecule of water. This equation is already balanced.

Common Mistake in Balancing Equations
1. Ignoring the law of conservation of matter.
2. Changing subscripts instead of coefficients.
3. Forgetting to simplify coefficients to smallest whole numbers.
4. Confusing reactants with products.

Simple Chemical Equation

Key Points and Definitions

Important Examples

1. Formation of Water (Synthesis)

2. Rusting of Iron (Oxidation)

3. Neutralization Reaction