Types of Chemical Reactions

⚗️ Synthesis & Decomposition Reactions

Part 1 of 7 — Building Up and Breaking Down

Chemistry is fundamentally about rearranging atoms. The simplest patterns involve either combining simple substances into a complex product or breaking a complex substance into simpler pieces. These two reaction types — synthesis and decomposition — are mirror images of each other.

🎯 Synthesis (Combination) Reactions

A synthesis reaction occurs when two or more reactants combine to form a single product.

General Form

$A + B \rightarrow AB$

Classic Examples

Key Pattern

Look for multiple reactants forming one product. The number of reactants is always greater than the number of products (which is 1).

Real-World Example

Rust formation is a synthesis reaction: $4\text{Fe} + 3\text{O}_2 \rightarrow 2\text{Fe}_2\text{O}_3$

⚗️ Decomposition Reactions

A decomposition reaction occurs when a single reactant breaks down into two or more simpler products.

General Form

$AB \rightarrow A + B$

Classic Examples

🎯 Synthesis vs. Decomposition — A Comparison

Synthesis & Decomposition Concept Quiz 🎯

Identify the Reaction Type 🧮

For each reaction, type synthesis or decomposition.

1) $2\text{Al} + 3\text{Br}_2 \rightarrow 2\text{AlBr}_3$

Fill in the Blanks — Synthesis & Decomposition 🔽

Exit Quiz — Synthesis & Decomposition ✅

🔄 Single & Double Replacement Reactions

Part 2 of 7 — Trading Partners

In replacement reactions, atoms or ions switch places. Understanding these reactions requires knowing which elements can displace others — that's where the activity series comes in.

📌 Single Replacement (Single Displacement)

A more reactive element displaces a less reactive element from a compound.

General Form

$A + BC \rightarrow AC + B$

Element A replaces element B in compound BC, but only if A is more reactive than B.

Examples

🔥 Combustion Reactions

Part 3 of 7 — Burning It Down

Combustion is one of the most important reaction types in chemistry and everyday life. From powering car engines to heating homes, combustion reactions release energy by reacting substances with oxygen gas.

📌 Complete Combustion of Hydrocarbons

When a hydrocarbon (a compound containing only C and H) burns in excess oxygen, the products are always carbon dioxide and water.

General Form

$\text{C}_x\text{H}_y + \left(x + \frac{y}{4}\right)\text{O}_2 \rightarrow x\text{CO}_2 + \frac{y}{2}\text{H}_2\text{O}$

⚖️ Balancing Chemical Equations

Part 4 of 7 — The Coefficient Method

A balanced equation has equal numbers of each type of atom on both sides. This is required by the Law of Conservation of Mass — atoms are neither created nor destroyed in a chemical reaction.

⚖️ Rules for Balancing Equations

What You CAN Do

• Change coefficients (the big numbers in front of formulas)

What You CANNOT Do

• Change subscripts (that changes the compound itself!)
• Add or remove substances

Step-by-Step Method

1. Write the unbalanced equation
2. Count atoms of each element on both sides
3. Balance one element at a time using coefficients
4. Start with the most complex substance or elements that appear in only one reactant and one product
5. Balance hydrogen and oxygen last (they often appear in multiple compounds)
6. Check that all atoms are balanced
7. Simplify coefficients to smallest whole numbers

Example: Balancing $\text{Al} + \text{O}_2 \rightarrow \text{Al}_2\text{O}_3$

🔮 Predicting Products

Part 5 of 7 — Using Reaction Types to Predict What Forms

One of the most important skills in chemistry is being able to look at reactants and predict what the products will be. The key is to first identify the reaction type, then apply the pattern for that type.

🎯 Product Prediction Strategy

Step 1: Classify the Reactants

Step 2: Apply the Pattern

🛠️ Problem-Solving Workshop

Part 6 of 7 — Identifying, Balancing, and Predicting

It's time to put together everything you've learned about reaction types. In this workshop, you'll practice the complete workflow: identify the reaction type, predict the products, and balance the equation.

📌 The Complete Workflow

Step 1: Identify the Reaction Type

Step 2: Predict Products

Apply the rules for that reaction type:

• Synthesis: combine to form one compound
• Decomposition: break into simpler substances
• Single replacement: check activity series, swap element
• Double replacement: swap cations, check for driving force
• Combustion: products are CO₂ + H₂O

Step 3: Write Correct Formulas

Use ion charges for ionic compounds. Don't forget subscripts!

Step 4: Balance the Equation

Use coefficients. Check every atom. Simplify to smallest whole numbers.

🎓 Synthesis & AP Review

Part 7 of 7 — AP-Style Questions on Reaction Classification

This final part brings together everything from the entire topic. You'll face AP-level questions that require you to classify reactions, predict products, balance equations, and apply your knowledge of the activity series, driving forces, and combustion patterns.

📋 Complete Reaction Type Summary