Synthesis (Combination) Reactions

Synthesis reactions, also known as combination reactions, involve two or more reactants combining to form a single product.

Definition: A synthesis reaction is a chemical process where two or more simple substances combine to form a more complex compound.

Recognition Clues:

• A single product is formed

Generic Equation: A + B → AB

Examples:

1. H₂ + O₂ → H₂O
2. Mg + O₂ → MgO
3. Fe + O₂ → Fe₂O₃
4. S + O₂ → SO₃

Highlight: In synthesis reactions, elements or simple compounds combine to form more complex substances.

Generic Equations:

1. M + O₂ → MO (where M is a metal)
2. X + O₂ → XO (where X is a non-metal)

Decomposition Reactions

Decomposition reactions are the opposite of synthesis reactions, where a single compound breaks down into simpler substances.

Definition: A decomposition reaction is a chemical process in which a single compound breaks down into two or more simpler substances.

Recognition Clues:

• A single reactant breaks down

Generic Equation: AB → A + B

Examples:

1. H₂O → H₂ + O₂
2. MgCO₃ → CO₂ + MgO

Example: The decomposition of water (H₂O) into hydrogen (H₂) and oxygen (O₂) through electrolysis is a classic example of a decomposition reaction.

Single Displacement Reactions

Single displacement reactions, also known as replacement reactions, involve an element replacing another element in a compound.

Definition: A single displacement reaction occurs when an element reacts with a compound, replacing one of its elements to form a new compound and a free element.

Recognition Clues:

• An element reacts with an ionic compound

Conditions:

1. For metals: The replacing metal must be higher on the activity series of metals.
2. For halogens: The replacing halogen must be higher on the periodic table.

Generic Equations:

1. A + BC → AC + B (where A is more reactive than B)
2. X + YZ → XZ + Y (where X is a more reactive halogen than Y)

Examples:

1. Li + Fe₂O₃ → Fe + Li₂O
2. Al + Na₂O → Al₂O₃ + Na
3. F₂ + HBr → HF + Br₂

Highlight: The reactivity of elements plays a crucial role in determining whether a single displacement reaction will occur.