1)氢氧化钙加到磷酸里,起初无现象,滴加一段时间后,出现沉淀(Ca(H2PO4)2->CaHPO4->Ca3(PO4)2)
(2)磷酸加到氢氧化钙里,起初产生沉淀,最终沉淀消失(Ca3(PO4)2->CaHPO4->Ca(H2PO4)2)
CaHPO4和Ca3(PO4)2都是沉淀
Ca(H2PO4)2可溶于水
$代表沉淀
(1)Ca(OH)2+2H3PO4=Ca(H2PO4)2+2H2O
Ca(H2PO4)2+Ca(OH)2=2CaHPO4$+2H20
2CaHPO4+Ca(OH)2=Ca3(PO4)2+2H2O
(2)3Ca(OH)2+2H3PO4=Ca3(PO4)2$+3H2O
Ca3(PO4)2+H3PO4=3CaHPO4
CaHPO4+H3PO4=Ca(H2PO4)2