Question

What is the chemical formula of calcium phosphate?
A.\[{\text{Ca}}{\left( {{\text{P}}{{\text{O}}_4}} \right)_2}\]
B.\[{\text{C}}{{\text{a}}_3}{\left( {{\text{P}}{{\text{O}}_4}} \right)_2}\]
C.\[{\text{C}}{{\text{a}}_3}\left( {{\text{P}}{{\text{O}}_4}} \right)\]
D.\[{\text{Ca}}\left( {{\text{P}}{{\text{O}}_4}} \right)\]

Answer 1

Hint:In a compound, to maintain its neutrality the net cationic or positive charge must be equal to net negative or anionic charge in the species. However compounds failing to balance its charge have either a positive or negative charge depending upon the net charge on reacting species.

Complete step by step answer:
The chemical formula of calcium phosphate is \[{\text{C}}{{\text{a}}_3}{\left( {{\text{P}}{{\text{O}}_4}} \right)_2}\] , as it is a salt with calcium ion as cation and phosphate ion as anion. The calcium carries \[ + 2\] charge in its ionic form and on the other hand, the phosphate ion carries \[ - 3\] charge. In order to maintain neutrality of a compound; positive charge must be equal to negative charge. Otherwise, a salt cannot be neutral. Now in case of calcium carbonate, cation is calcium ion which carries \[ + 2\] charge and anion is phosphate ion which carries \[ - 3\] charge, so to have a neutral salt of calcium phosphate three calcium ions must combine with two phosphate ions which corresponds to net charge zero. The total cationic or positive charge in calcium phosphate is \[ + 6\] but it is neutralized by the total anionic or negative charge of phosphate ion \[ - 6\] .
We can also take an example of lime or calcium oxide which has the chemical formula of \[{\text{CaO}}\] . As in this case, one calcium ion which tends to carry \[ + 2\] charge combines with one oxygen ion which carries \[ - 2\] charge. The overall net charge on calcium oxide will be zero.

Thus, the correct option is B.

Note:
Oxidation state shows the total number of electrons which have been removed from an element with positive oxidation state or added to an element with a negative oxidation state to get its present state.