Phosphoric acid, or H3PO4, plus calcium hydroxide, or Ca(OH)2, react to form water and calcium phosphate. Water is H2O, and calcium phosphate is Ca3(PO4)2. Lab technicians need two moles, or parts, of phosphoric acid and three moles of calcium hydroxide to form six moles of water and one mole of calcium phosphate. The entire chemical equation is represented as: 2 H3PO4 + 3 Ca(OH)2 = 6 H2O + Ca3(PO4)2.
Using the coefficients to the left of each chemical, there is a total of six hydrogen atoms, six hydroxide molecules, three calcium atoms and two phosphate molecules on each side of the equation. An acid and a base combine to form water and a salt.
In order to balance this chemical equation, the calcium and hydrogen ions are switched on the product side, and then the correct amounts of each substance are added. Ions are equal on the reactant and product sides. The coefficients indicate how much of each molecule, or molar mass, is needed to carry out the reaction.
Phosphoric acid is used to make agricultural fertilizers and to flavor soft drinks. Calcium hydroxide is a strong base made by mixing lime powder, or calcium oxide, with water. Calcium phosphate is commonly used in supplements for patients who do not have enough calcium in their diet.