1)Mr(HCl)= 1+ 35.5= 36.5
w(H)= 1/36.5=0,027 = 2.7%
w(Cl)=35.5/36.5=0,973=97.3%
2) Mr(Na2CO3)=46+12+48=106
W(Na)=46/106=0.434=43.4%
w(C)= 12/106=0.113=11.3%
w(O)= 48/106=0.453=45.3%
3) Mr(KMnO4)=39+55+64=158
w(K)=39/158=0.247=24.7%
w(Mn)=55/158=0.348=34.8%
w(O)=64/158=0.405=40.5%
4)Mr(NaOH)=23+16+1=40
w(Na)=23/40=0.575=57.5%
w(O)=16/40=0.4=40%
w(H)=0.025=2.5%