Question

Calcium phosphate can be obtained by reacting calcium hydroxide with:
A. phosphoric acid
B. sulfuric acid
C. nitric acid
D. both (B) and (C)

Answer 1

Calcium phosphate has the chemical formula $C{a_3}{\left( {P{O_4}} \right)_2}$. It is an inorganic salt of calcium and phosphate. Calcium hydroxide is an inorganic salt of calcium and hydroxide ions. The hydroxide needs to be substituted with a phosphorous oxide to obtain the phosphate salt.

Complete step by step answer:
Calcium phosphate is an inorganic compound consisting of calcium ions ($C{a^{2 + }}$) and phosphate ions. Calcium phosphate is usually found in several living organisms. It is one the important component of bone mineral and tooth enamel.
Calcium phosphate exists in a colloidal form in micelles which is bound to casein protein with magnesium and zinc. This is known as colloidal calcium phosphate (CCP). The calcium phosphates also remain in the form of oxide and hydroxide in the proteins. They appear as white solids and are of nutritious value.
Calcium hydroxide is an inorganic compound of calcium ions ($C{a^{2 + }}$) and hydroxide ion ($O{H^ - }$). Let us determine the reaction of calcium hydroxide with given compounds.
A. phosphoric acid
The chemical reaction of calcium hydroxide with phosphoric acid (${H_3}P{O_4}$) produces calcium phosphate and water. The reaction is
$3Ca{\left( {OH} \right)_2}\; + \;2{H_3}P{O_4}\; \to \;C{a_3}{\left( {P{O_4}} \right)_2}\; + \;6{H_2}O$
B. sulfuric acid
The chemical reaction of calcium hydroxide with sulfuric acid (${H_2}S{O_4}$ ) produces calcium sulfate and water. The reaction is
$Ca{\left( {OH} \right)_2} + {H_2}S{O_4} \to CaS{O_4} + 2{H_2}O$
C. nitric acid
The chemical reaction of calcium hydroxide with nitric acid ($HN{O_3}$ ) produces calcium nitrate and water. The reaction is
$Ca{\left( {OH} \right)_2} + 2HN{O_3} \to Ca{\left( {N{O_3}} \right)_2} + 2{H_2}O$
Hence, option A is the correct answer, i.e. calcium phosphate can be obtained by reacting calcium hydroxide with phosphoric acid.

Note:
Calcium phosphate minerals are primarily used for generating phosphoric acid and fertilizers. Excess use of calcium phosphate results in adverse effects on the nutrient-containing surface of agricultural fields.