Summary of "3.1 Chemical Reactions and Chemical Equations | General Chemistry"

This lesson introduces the fundamental concepts of chemical reactions and chemical equations as part of a broader chapter on Stoichiometry. The instructor, Chad from Chad’s Prep, aims to simplify learning chemistry by explaining five main types of chemical reactions, how to predict their products, and how to balance chemical equations. The lesson also touches on the significance of ionic charges in forming compounds and provides practical balancing strategies.

Main Ideas and Concepts

Introduction to Stoichiometry and Chemical Reactions
- Stoichiometry involves moles and Avogadro’s number, but this lesson focuses on introducing chemical reactions and equations.
- Five key types of reactions will be covered: combination, decomposition, combustion, double replacement, and single replacement.
- Balancing chemical equations is a critical skill taught alongside reaction types.
Combination Reactions
- Two or more reactants combine to form one product.
- Example: Sodium (metal) reacts with chlorine (non-metal) to form Sodium chloride (ionic compound).
- Important to balance charges in ionic compounds; the overall charge must be zero.
- After correct formulas are determined, coefficients balance the atoms on each side of the equation.
Decomposition Reactions
- A single reactant breaks down into two or more products.
- Often thermal decomposition (requires heat, denoted by Δ).
- Example: Calcium carbonate decomposes into Calcium oxide and carbon dioxide.
- Usually, products are given; predicting products is not expected at this stage.
- Equations must be balanced but often are straightforward.
Combustion Reactions
- Combustion is the reaction of a substance with oxygen.
- Requires oxygen; no combustion on the moon due to lack of atmosphere.
- Hydrocarbon combustion always produces carbon dioxide (CO₂) and water (H₂O).
- Balancing combustion reactions involves:
  - Start by balancing carbon atoms.
  - Then balance hydrogen atoms.
  - Save oxygen for last because it appears in multiple products.
- Example: Combustion of Propane (C₃H₈).
Double Replacement (Double Displacement) Reactions
- Occur mostly in aqueous solutions.
- Cations and anions swap partners.
- Example: Silver nitrate reacts with sodium sulfide to form silver sulfide and sodium nitrate.
- Charges must balance to form correct ionic formulas.
- Coefficients are adjusted to balance the overall equation.
- Polyatomic ions remain intact and are balanced as a unit.
- Solubility rules (to be covered later) determine if products are aqueous or solids.
Single Replacement Reactions
- One element replaces another in a compound.
- Also occur in aqueous solutions.
- These are a type of redox (oxidation-reduction) reaction.
- Example: Zinc replaces copper in copper chloride to form zinc chloride and copper metal.
- Balancing is generally straightforward.
- Further details on redox reactions will be covered in later chapters.
General Notes
- Coefficients balance atoms; subscripts define chemical formulas and cannot be changed when balancing.
- Charges must balance in ionic compounds.
- Heat is often required for decomposition reactions.
- Combustion reactions always involve oxygen and produce CO₂ and H₂O when hydrocarbons are involved.
- Double and single replacement reactions are aqueous reactions, typically occurring in water.
- More detailed discussions on solubility and redox reactions will follow in later lessons.

Methodology / Instructions for Balancing Reactions

Balancing Ionic Compounds
- Determine the charge of each ion (based on periodic table position or memorized charges).
- Write the formula so that total positive and negative charges balance to zero.
- Do not change subscripts once the formula is correct.
Balancing Chemical Equations
- Start by balancing elements that appear in only one reactant and one product.
- Save elements that appear in multiple compounds/products (like oxygen in combustion) for last.
- Use coefficients (numbers in front of formulas) to balance atoms on both sides.
- Check that the total number of atoms for each element is equal on both sides.
- For polyatomic ions that appear unchanged on both sides, balance them as a single unit.
Balancing Combustion Reactions
1. Balance carbon atoms first.
2. Balance hydrogen atoms second.
3. Balance oxygen atoms last.
4. Adjust coefficients for oxygen molecules (O₂) accordingly.
Predicting Products
- Combination: Two or more reactants combine into one product.
- Decomposition: One reactant breaks down into multiple products.
- Combustion: Hydrocarbon + O₂ → CO₂ + H₂O.
- Double Replacement: Exchange cations and