There are three major types of reactions with water.

1. A PURE METAL or a METAL HYDRIDE react with water to produce a BASE and HYDROGEN GAS (H₂).

Metal hydride - A positive metal ion bonded to H with an oxidation state of -1
NOTE:  The bases produced may be soluble and should be written as their respective ions.  See Solubility Rules.

• Sodium metal is added to distilled water.

• Calcium metal is added to distilled water.

• Solid calcium hydride is added to distilled water.

• Solid lithium hydride is added to distilled water

2. A METAL OXIDE reacts with water to produce a BASE.

Metal oxide - A positive metal ion bonded to O with an oxidation state of -2.  Metal oxides are called basic anhydrides because they produce bases when they are added to water.
NOTE:  There is no H present in a metal oxide, so no hydrogen gas is produced.
NOTE:  The bases produced may be soluble and should be written as their respective ions.  See Solubility Rules.

• Solid potassium oxide is added to water.

• Solid barium oxide is added to water.

• Solid lithium oxide is added to water.

• Solid calcium oxide is added to water.

3. A NONMETAL OXIDE reacts with water to produce an ACID.

Nonmetal oxide - A nonmetal with a positive oxidation state bonded to O with an oxidation state of -2.  Nonmetal oxides are called acid anhydrides because they produce acids when they are added to water.
NOTE:  Strong acids dissociate nearly completely in water and should be written as their respective ions.  Weak acids dissociate only slightly in water and should be written as a solid compound.
NOTE:  When determining which acid will form where there is more than one possibility (e.g. HNO₂ or HNO₃), the formula of the acid formed can generally be found by adding up all the reactant atoms and simplifying to the simplest whole-number ratio of atoms.

• Solid dinitrogen pentoxide is added to water.

• Carbon dioxide gas is bubbled through water.

• Solid phosphorus (V) oxide is added to distilled water.

• Sulfur dioxide gas is bubbled through water.

• Sulfur trioxide gas is bubbled through water.

Next:  "Overview of Acid-Base Reactions"