a) [tex]Na^{I}PO_{4}^{III}=>Na_{3}PO_{4}[/tex]
b) 3:1:4
c)
69g Na.......31g P..... 64g O........164g Na3PO4
x....................y.................z................100g Na3PO4
x = 69*100/164 = 42,07% Na
y = 31*100/164 = 18,9% P
z = 100 - 42,07 - 18,9 = 39,03% O
d)
[tex]M_{Na_{3}PO_{4}}=3M_{Na}+M_{P}+4M_{O}=69+31+64=164g/mol[/tex]
