A mass of 21.5 grams of calcium hydroxide reacts with an excess of phosphoric acid. what mass of calcium phosphate could be recovered from solution?

The balanced equation for the above reaction is as follows;

3Ca (OH) ₂ + 2H₃PO₄ - - - > Ca₃ (PO₄) ₂ + 6H₂O

stoichiometry of Ca (OH) ₂ to Ca₃ (PO₄) ₂ is 3:1

Since Ca (OH) ₂ is the limiting reactant, amount of Ca₃ (PO₄) ₂ formed depends on the amount of Ca (OH) ₂ present

Number of Ca (OH) ₂ reacted - 21.5 g/74 g/mol = 0.29 mol

Therefore number of Ca₃ (PO₄) ₂ moles formed - 0.29 mol/3 = 0.0967 mol

Mass of Ca₃ (PO₄) ₂ formed - 0.0967 mol x 310 g/mol = 30.0 g