What mass of phosphoric acid can be obtained if 32 kg of calcium phosphate is calcined with coal and sand, the resulting phosphorus is burned and the combustion product is dissolved in water?
Сa₃ (PO₄) ₂ + 5C + 3SiO₂ = 3CaSiO₃ + 2P ↑ + 5CO ↑
n (Сa₃ (PO₄) ₂) = n (P) / 2
4P + 5O₂ (g) = 2P₂O₅
n (P) / 4 = n (P₂O₅) / 2 or n (P) / 2 = n (P₂O₅) = n (Ca₃ (PO₄) ₂)
P₂O₅ + 3H₂O = 2H₃PO₄
n (P₂O₅) = n (H₃PO₄) / 2
n (Сa₃ (PO₄) ₂) = m / M = 32 kg / 310 kg / kmol = 0.103 kmol
since n (P₂O₅) = n (Сa₃ (PO₄) ₂) = 0.103 kmol, then
n (H₃PO₄) = 2 * n (P₂O₅) = 2 * 0.103 kmol = 0.206 kmol
m (H₃PO₄) = n * M = 0.206 kmol * 98 kg / kmol = 20.188 kg.
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