H2O: M(H2O)=2+16=18 г/моль
w(O)=16/18*100%=88,89%
HNO3: M(HNO3)=1+14+48=63 г/моль
w(O)=48/63*100%=76,19%
Al(OH)3: M(Al(OH)3)=27+17*3=78 г/моль
w(O)=48/78*100%=61,54%
Сa3(PO4)2: M(Сa3(PO4)2)=40*3+31*2+16*8=270 г/моль
w(O)=128/270*100%=47,41%
H2SO4: M(H2SO4)=2+32+48=82 г/моль
w(O)=64/82*100%=78,05