Superphosphate of lime — a phosphate fertilizer — is obtained by which reaction?
A.Calcium phosphate with sodium hydroxide
B.Calcium phosphate with sulphuric acid✓ Correct
C.Calcium phosphate with hydrogen chloride
D.Calcium phosphate with nitric acid
Explanation
Superphosphate of lime (calcium superphosphate) is manufactured by treating finely powdered calcium phosphate (or rock phosphate, Ca₃(PO₄)₂) with concentrated sulphuric acid. The reaction is: Ca₃(PO₄)₂ + 2H₂SO₄ → Ca(H₂PO₄)₂ + 2CaSO₄. The product is a mixture of calcium dihydrogen phosphate (water-soluble, providing available phosphorus) and calcium sulphate. This was historically one of the earliest commercial phosphate fertilizers.
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