Ca sa calculezi compozitia procentuala a unei substante, afli mai intai masa molara, si dupa calculezi cat la suta reprezinta fiecare element din aceasta.
[tex] M_{HCl}= A_{H}+ A_{Cl}=1+35,5=36,5. \\ \\ 36,5g~HCl.............1g~H .............35,5g~Cl \\ 100g~HCl...............xg~H.............yg~Cl \\ -------------------- \\ x= \frac{100*1}{36,5} =2,73(\%~H) \\ y=100\%-2,73\%=97,27(\%~Cl)[/tex]
[tex] M_{ H_{2}S O_{4} }=2 A_{H}+ A_{S} +4 A_{O}= \\ ~~~~~~~~~~~~= 2*1+32+4*16= \\ ~~~~~~~~~~~~= 2+32+64\\ ~~~~~~~~~~~~=98 \\ \\ 98g~ H_{2}S O_{4} .............2g~H .............32g~S.............64g~O \\ 100g~ H_{2}S O_{4}...........xg~H.............yg~S...............zg~O \\ ------------------------ \\ x= \frac{100*2}{98}= 2,04(\%~H) \\ y= \frac{100*32}{98}= 32,65(\%~S) \\ z=100\%-2,04\%-32,65\%=65,31(\%~O)[/tex]
