Question

Superphosphate of lime is obtained by treating:
A) calcium phosphate with ${\text{HCl}}$
B) calcium phosphide with ${\text{HCl}}$
C) calcium phosphate with ${{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}}$
D) calcium phosphate with ${\text{NaOH}}$

Answer 1

Hint :The compound superphosphate, also known as superphosphate of lime, is made by reacting rock phosphate with sulfuric acid, phosphoric acid, or a combination of the two. It is the primary carrier of phosphate, the plant-usable source of phosphorus, and one of the most effective fertilisers on the planet.

Complete Step By Step Answer:
Ordinary superphosphate has around $20\,\% $ available phosphate, while double superphosphate (also known as triple superphosphate) has $40 - 50\,\% $ available phosphate.
The first chemical fertiliser was superphosphate. Bonemeal and sulfuric acid were used to make it for the first time around 1840. Superphosphate was made from rock phosphate ore by treating it with sulfuric acid a short time later. Ordinary superphosphate, also known as single superphosphate, is the name given to this substance.
Superphosphate of lime is obtained by treating calcium phosphate with ${{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}}$
$
  C{a_3}{\left( {P{O_4}} \right)_2}\,\, + \,\,{H_2}S{O_4}\,\, \to \,\,2CaS{O_4}\,\, + \,\,Ca{\left( {{H_2}P{O_4}} \right)_2} \\
  \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,{\text{superphosphate}}\,{\text{of}}\,{\text{lime}} \\
 $
Hence, the correct option is C.

Additional Information:
Today, almost all the superphosphate is a triple superphosphate. Superphosphates have usable phosphorus in the form of monobasic calcium phosphate, which is soluble enough to nourish crops. Ordinary superphosphate contains gypsum, which dilutes the monobasic calcium phosphate concentration, while triple superphosphate contains only monobasic calcium phosphate.

Note :
The superphosphate of lime has been found to increase the exchangeable calcium in an infertile acid soil. It did not appear to be involved in the nitrogen fixation process, but it did increase plant nitrogen uptake.