Chapter 11

Balancing
Reaction

Each side of the equation has the same amount of atoms of each element and mass is conserved

Example
Unblanced: H2O2 —> H20 + O2
Balanced: 2H202 —> 2H2O + O2

Word Equations

Reactants are on the left and products are on the right. An arrow separates them, arrows mean yields, gives, reacts, to produce

Examples
Iron + oxygen —> Iron(iii) oxide

Examples:
Sodium phosphate and calcium chloride react to form calcium phosphate and sodium chloride.

Reaction Types

Combination

2 or more substances react to form a single substance

Examples
2Mg + O2 —> 2MgO
2K + 2Cl —> 2KCl

Decomposition

A single compound is broke down into simpler substances.

Examples
2HgO —> 2Hg + 2O
2NaN3 —> 2Na + 3N2

Single Replacement

The atoms of one elements replace the atoms of a second element in a compound

Examples
2K + H2O —> 2KOH + 2H
Zn + Cu(NO3)2 —> Cu + Zn(NO3)2

Double Replacement

Exchange of positive ions between 2 compounds

Examples
Na2S + Cd(NO3)2 —> CdS + 2NaNO3
2NaCN + H2SO4 —> 2HCN + Na2SO4

Combustion

When the supply of oxygen is low, the combustion will not be completed, allowing the possibility that carbon(soot) and/or carbon monoxide gas will be among the products

A complete combustion of a hydrocarbon produces carbon dioxide and water.

Examples
C2H6 + 3O2 —> 2CO2 + 3H2O
2C8H18 + 25O2 —> 16CO2 + 18H2O

Net Ionic Reactions

Shows only spectator ions, ions that are the same on both sides of the equation, involved in a chemical reaction and is balanced with respect to both mass and charge

Predicting Products

By using the general rules for solubility of ionic compounds, you can predict the formation of a precipitate.

If a substance is soluble, then it is aqueous and will not form a precipitate.

If it is insoluble, than a precipitate will form in the new solution.