Дано:
Ba S O4
W(Ba)-?
W(S)-?
W(O)-?​

W=n*Ar
—— *100%
Mr
Mr(BaSO4)=Ba+S+O*4=137+32+16*4=233
W(Ba)=1*137
——- *100%. =58,8%
233
W(S)=1*32
——. *100%. =13,7%
233
W(O)= 4*16
——. *100%. = 27,5%
233