Reaction Types

Single Displacement Reactions

A more reactive metal displaces a less reactive metal (in some compound) or a more reactive nonmetal replaces a less reactive nonmetal in a compound.
In water solutions a more reactive metal + compound with a less reactive metal yields the less reactive metal plus a compound with the more reactive metal . These are oxidation-reduction reactions in which electrons are transferred from a metal to a nonmetal

General equation: A + BC --> B + AC

General form: element + compound --> element + compound

example: Zn (s) + Cu(N0₃)₂ (aq.) --> Cu (s) + Zn(N0₃)₂ (aq.)

example: Cu (s) + 2AgN0₃ (aq.) --> 2Ag + Cu(N0₃)₂ (aq.)

example: Mg (s) + 2HC1 (aq.) --> ? (g) + ? (aq.)

Double Displacement Reactions

The metals present in two compounds change places to form two new compounds.

Examples are precipitation reactions and acid-base reactions.

General equation: AB + CD --> AD + CB

General form: compound + compound --> compound + compound

example: AgN0₃ (aq.) + NaCl (s) --> AgCl (s) + NaN0₃ (aq.)

example: NaOH (aq.) + HCl (aq.) ‑--> NaCl (s) + H₂O(1)

example: Ba(N0₃)₂ (aq.) + Na₂SO₄ (aq.) --> ? + >

Synthesis Reactions (Direct combination)

- 2 or more substances combine to form one new substance.

- General equation: A + B --> AB

example: 2H₂ (g) + O₂ (g) --> 2H₂O (l)

example: CaO (s) + H₂O (l) --> Ca(OH)₂ (aq.)

example: Ca (s) + Cl₂ (g) --> CaCl₂ (s)

example: SO₂ (g) + H₂O (l) --> ___________ (aq.)

example: 4Al (s) + 3O₂ (g) --> ______________ (s)

Decomposition Reactions

- A compound is broken down into 2 or more elements.

- Energy must be supplied to break the complex compound into simpler substances.

- General equations: AB --> A + B or ABC --> A + BC

example: 2HgO (s) --> 2Hg (l) + O₂ (g)

example: 2H₂O (l) --> 2H₂ (g) + O₂ (g)

example: H₂O₂ (l) --> H₂ (g) + O₂ (g)

example: 2KClO₃ (s) --> __________ (s) + ___________ (g)

Other Reaction Types:

1. dehydration - removal of water (water must be a product)

- example: CuSO₄_×5H₂O (s) --> CuSO₄ (s) + H₂O (l)

2. polymerization - using a subunit molecule (called a monomer) as a

building block of a many unit chain or structure

- examples: DNA, RNA, proteins, carbohydrates, rubber

3. hydrogenation - adding hydrogen

4. combustion - some substance burning in oxygen (from the air usually)

to produce CO₂ and H₂O (if combustion is incomplete

it may produce CO)

5. neutralization - combining an acid with a base to form a salt and water

example: NaOH + HCl --> NaCl + H₂O