Question

The formula of calcium dihydrogen phosphate is:
A. \[Ca{\left( {{H_2}P{O_4}} \right)_2}\]
B. $Ca{\left( {HP{O_4}} \right)_2}$
C. $C{a_3}HP{O_4}$
D. $C{a_3}{\left( {{H_2}P{O_4}} \right)_2}$

Answer 1

Hint: To answer this question you should recall the names of the various ions formed by phosphorus and their charges. Phosphate, dihydrogen phosphate and hydrogen phosphates are formed by the loss of protons from orthophosphoric acid.

Complete step by step answer:
-Phosphorus forms many different anions with oxygen. Most of the ions are derived from phosphate ions ${\left[ {P{O_4}} \right]^{3 - }}$. The phosphate ion is formed by loss of three protons from phosphoric acid.
-Loss of one proton from phosphoric acid gives dihydrogen phosphate ion ${\left[ {{H_2}P{O_4}} \right]^ - }$.
-Loss of another proton gives hydrogen phosphate ion ${\left[ {HP{O_4}} \right]^{2 - }}$.
In the question, you need to find the formula for calcium dihydrogen phosphate.
-It is known that dihydrogen phosphate is an anion carrying the charge $ - 1$.
-It should be known that calcium forms a cation with $ + 2$ charge in the majority of compounds.So, to balance the $ + 2$ charge on calcium, 2 molecules of dihydrogen phosphate need to form an ionic bond with it.
Thus, you get the formula for calcium dihydrogen phosphate as
\[Ca{\left( {{H_2}P{O_4}} \right)_2}\].

Hence option A is correct.

Additional information:
Calcium dihydrogen phosphate is mainly used in fertilizers and is known as superphosphate fertilizer. It has a very high phosphorus content and thus is ideal for encouraging strong root development in plants. It also improves the ripening of fruits and vegetables.
It is also used in the food industry in baked products. As it is acidic in nature, it reacts with baking soda to produce carbon dioxide gas causing the baked goods to rise.

Note:
Commonly, Calcium dihydrogen phosphate is found as a monohydrate, that is, \[Ca{\left( {{H_2}P{O_4}} \right)_2}.{H_2}O\].
Apart from the IUPAC name calcium dihydrogen phosphate, this compound has various other names like
1.Acid calcium phosphate
2.Calcium biphosphate
3.Monobasic calcium phosphate
4.Phosphoric acid calcium salt (2:1)