Question

P→P2O5→H3PO4→Na3PO4→Ca(PO4)2

Answer 1

$P-P2O5-H3PO4-Na3PO4-Ca(PO4)2$
$4P + 5O2 = 2 P2O5$
$P2O5 + 3H20 = 2H3PO4$
$H3PO4+3NaOH = Na3PO4+3H20$
$Na3PO4+3Ca (OH) 2 = Ca3(PO4)2 +3NaOH$