Structure of Calcium Hydroxide

Chalk - Source of Calcium Oxide and Calcium Hydroxide

Calcium, symbol Ca, is a soft metal whose atomic number is 20 on the periodic table. It is an "alkaline earth" metal with a valence of +2. This means it loses two electrons when forming compounds. Calcium reacts with water to form calcium hydroxide.

Water

Water has a pH of 7.0. A pH of 0 represents a very strong acid while a pH of 14.0 represents a very strong base. Although water is neutral, it can be looked at as a very weak acid or a very weak base.

Reaction

When reacting with calcium, water acts as an acid:

Ca + 2H₂O ' Ca(OH)₂ + H₂'

Structure

Drawing it out in full, the structure for calcium hydroxide is:

H-O-Ca-O-H

The dashes between the symbols are chemical bonds joining the atoms.

Another Preparation

Calcium hydroxide is called "slaked lime." This means it can be formed from lime by slaking. Lime is calcium oxide, or CaO. To slake it means to "satisfy its thirst." The reaction is,

CaO + H₂O ' Ca(OH)₂

Use to Make Other Compounds

Calcium hydroxide can be used to prepare other calcium compounds by reacting with acids. For example, calcium chloride is prepared by using hydrochloric acid.

Ca(OH)₂ + 2HCl ' CaCl₂ + 2H₂O

References

• ChemicalLand21.com: Calcium Hydroxide
• Organic Materials Review Institute: Calcium Hydroxide