In the reaction, 2 H3PO4(aq) + 3 Ca(OH)2(aq) 6 H2O(l) + Ca3(PO4)2(aq), how many grams of H3PO4 will be produced from 326.4 grams of Ca3(PO4)2?

Answer 1

2H₃PO₄(aq) + 3Ca(OH)₂(aq) <==> Ca₃(PO₄)₂(aq) + 6H₂O(l)

Assuming that you are indeed speaking of the reverse reaction to form H₃PO₄, then...

326.4 g Ca₃(PO₄)₂ x 1 mol / 310.4 g x 2 mol H₃PO₄ / mol Ca₃(PO₄)₂ x 97.99 g/mol = 206.1 g H₃PO₄