a)
m H₃PO₄ = 3* 1u+ 31u + 4*16u=98u
% H = 3u/98u*100%= 3,06%
% P = 31u/98u*100%= 31,63%
% O= 64u/98u*100%= 65,31%
b)
m CuSO₃ = 64u + 32u+ 3*16u= 144u
% Cu = 64u/144u*100%= 44,44%
% S = 32u/144u*100%= 22,22%
% O = 48u/144u*100%= 33,33%
c)
m Cl₂O₅ = 2*35,5u + 5*16u= 71u+ 80u= 151u
% Cl = 71u/151u*100%= 47,02%
% O= 80u/151u*100%= 52,98%
