Question

What is the chemical formula of triple superphosphate
(a) \[\text{C}{{\text{a}}_{2}}({{\text{H}}_{2}}\text{P}{{\text{O}}_{4}}).2{{\text{H}}_{2}}\text{O}\]
(b) \[\text{C}{{\text{a}}_{2}}{{({{\text{H}}_{2}}\text{P}{{\text{O}}_{4}})}_{2}}.{{\text{H}}_{2}}\text{O}\]
(c) \[\text{C}{{\text{a}}_{2}}({{\text{H}}_{2}}\text{P}{{\text{O}}_{4}}).3{{\text{H}}_{2}}\text{O}\]
(d) \[\text{CaS}{{\text{O}}_{4}}.3{{\text{H}}_{2}}\text{O}\]

Answer 1

Hint: We know that Triple Super Phosphate (TSP) is used as fertilizer composed of nutrients that are used to restore soil components essential for farming. It is manufactured by reacting insoluble phosphate rock with sulfuric acid to form a mixture of soluble mono-calcium phosphate and calcium sulphate which is able to be used by plants.
Complete step by step solution:
>The formula of triple superphosphate fertilizer, shortly called as TSP, is $\text{Ca(}{{\text{H}}_{2}}\text{P}{{\text{O}}_{4}}{{)}_{2.}}{{\text{H}}_{2}}\text{O}$(43-44% ${{\text{P}}_{2}}{{\text{O}}_{5}}$) . When it dissolves in water, its phosphorus is negatively charged (-1). While a part of phosphorus content in TSP can dissolve in water, the rest is in ammonium citrate. However, both of them are in plant absorbable forms.
> We should know one more kind of superphosphate and is called a normal superphosphate.
The formula of normal superphosphate fertilizer, briefly referred to as NSP, is $3\text{Ca(}{{\text{H}}_{2}}\text{P}{{\text{O}}_{4}}{{)}_{2}}.{{\text{H}}_{2}}\text{O+7CaS}{{\text{O}}_{4}}$. The letter (N) in NSP abbreviation refers to the word “normal” rather than nitrogen (N) as in other nitrogenous fertilizers. So there is no nitrogen in NSP.
> NSP and TSP fertilizers are preferred as starter fertilizer for low pH soils in which tea and hazelnut are cultivated and for areas where high-quality tobacco is grown. It can be used for all plants that are grown in the soils with low or moderate phosphorus availability. When phosphorus is applied less than required or applied phosphorus has low efficiency due to soil conditions, fine root development and plant growth are reduced and as a result of this, yield is good.
Therefore, the correct option is (b)$\text{Ca(}{{\text{H}}_{2}}\text{P}{{\text{O}}_{4}}{{)}_{2.}}{{\text{H}}_{2}}\text{O}$.

Note: We should know that if TSP is used in strongly acidic soils, its phosphorus incorporated with Fe and Al might convert into unavailable forms. In such cases, lime application must be done 2-3months prior to the fertilizer use and soil pH must be increased up to around 6.5. When used in calcareous soils, the effectiveness of TSP fertilizer decreases.