Concept 8 - Classifying Reactions

Why do we classify chemical reactions?

To make it easier to predict the products of a reaction.

What are the 5 types of chemical reactions?

• Synthesis

• Decomposition

• Combustion

• Single Replacement

• Double Replacement

What happens during a synthesis reaction?

Two or more reactants combine to form one new compound (A + B → AB).

Example of a synthesis reaction

2Na (s) + Cl₂ (g) → 2NaCl (s)

What is an oxide in a synthesis reaction?

A binary compound with at least one atom of oxygen.

What happens during a decomposition reaction?

One reactant breaks down into two or more simpler compounds (AB → A + B).

What usually causes decomposition reactions?

Addition of energy (heat or electricity).

What is electrolysis?

Decomposition of a substance using electric current.

What happens during a combustion reaction?

A substance reacts with oxygen, often releasing heat and light.

Typical products of hydrocarbon combustion?

Carbon dioxide (CO₂) and water (H₂O).

What happens during a single replacement reaction?

One element replaces another in a compound (A + BC → B + AC).

Example of a single replacement reaction?

2Al (s) + 3Pb(NO₃)₂ (aq) → 3Pb (s) + 2Al(NO₃)₃ (aq)

What happens when a metal reacts with water?

It forms a metal hydroxide and hydrogen gas.

What happens during a double replacement reaction?

Ions of two compounds exchange places to form two new compounds (AB + CD → AD + CB).

What are typical products of double replacement reactions?

• A precipitate (solid)

• An insoluble gas

• A molecular compound like water

Example of a double replacement reaction

NaCl (aq) + AgNO₃ (aq) → AgCl (s) + NaNO₃ (aq)

What is an activity series?

A list showing elements in order of how easily they undergo chemical reactions.

How do metals behave according to the activity series?

Metals with greater activity lose electrons more easily.

How do nonmetals behave according to the activity series?

Nonmetals with greater activity gain electrons more easily.

In single replacement reactions, which elements can replace others?

An element can replace any element below it on the activity series, but not one above it.