Question

Please help me

Na2SO3+...=H2SO4

CaSO3+...=H2SO4

SO2+...=MgSO3

Ca3PO4=P

H3PO4+...=Ca(H2PO4)2

P+...=Mg3P2

SiO2+...=Mg2Si

Answer 1

One adds water to the first two, MgS for the third, the 4th requires quite a decomposition (malformed substance -- probably Ca3(PO4)2 ), 5th is with hydrogen, 6 with atomic magnesium while the 7th also with atomic magnesium.