Question

(i) Calculate the percentage of phosphorus in the fertilizer superphosphate Ca(H₂PO₄)₂.
(H = 1; O = 16; P = 31; Ca = 40)
(ii) Write out and balance the following equation correctly:
Ca₃(PO₄)₂ + H₂SO₄ $\stackrel{}{\to }$ Ca(H₂PO₄)₂ + CaSO₄
(iii) Copy and complete the following sentence:
Superphosphate is an example of a compound called___________(acid salt / basic salt / normal salt).

Answer 1

(i) Molar mass of Ca(H₂PO₄)₂ = (40 + (2 + 31 + 64)$\times$2) g = 234 g mol^-1

Amount of phosphorous in 234 g of superphosphate = (31$\times$2) g = 62 g

Percentage of phosphorus in superphosphate = $\left(\frac{62}{234}\right)\times 100=26.5\%$

(ii) Balanced equation of the above reaction is:

Ca₃(PO₄)₂ + 2H₂SO₄ → Ca(H₂PO₄)₂ + 2CaSO₄

(iii) Superphosphate is an example of a compound called acid salt.