Unit 5: Chemical Formulas and Equations

Unit 5: Chemical Formulas and Equations

Chemical Formulas:

1. Definition:

   • Chemical formulas are symbolic representations of compounds, indicating the types and numbers of atoms present.

2. Types of Formulas:

   • Molecular Formula:
     • Represents the actual number of each type of atom in a molecule.
   • Empirical Formula:
     • Represents the simplest whole-number ratio of different atoms in a compound.

3. Representation:

   • Elements are represented by symbols (e.g., $O$ for oxygen).
   • Compounds are represented by combinations of symbols (e.g., $H_{2}O$ for water).

Chemical Equations:

1. Definition:

   • Chemical equations are symbolic representations of chemical reactions, showing the reactants and products involved.

2. Basic Format:

   • $\text{Reactants}\to \text{Products}$

3. Balancing Equations:

   • Equations must be balanced to satisfy the Law of Conservation of Mass.
   • Coefficients are used to balance equations, representing the number of moles of each substance.

4. State Symbols:

   • Indicate the physical state of substances (solid, liquid, gas, aqueous solution).

5. Conservation of Mass:

   • The total mass of the reactants equals the total mass of the products.

6. Limiting Reactant:

   • The limiting reactant is the substance that is completely consumed in a reaction.

7. Yields:

   • The arrow in a chemical equation indicates the direction of the reaction.

Student Goals

• Recognize the difference between a chemical formula and a chemical equation.
• Identify a simple balanced chemical equation.
• Identify chemical equations that are examples of the law of conservation of mass.
• Cite evidence, determined from an experiment using chemical equations, to support the law of conservation of mass.

Unit Focus

• Know the difference between an element, a molecule, and a compound.
• Understand that there is conservation of mass and energy when matter is transformed.