Question

вычислите массовые доли элементов P2O5

Answer 1

$w(P)=frac{2cdot{Ar(P)}}{Mr(P_2O_5)}=frac{2cdot31}{2cdot3+5cdot16}=frac{62}{112}=55,36%\w(O)=100%-w(P)=100-55,36=44,64%$

Answer 2

                         P2 O5

                     31*2: 16*5

                         31:40

W(P)=(100%:71)*31=43,66%;

W(O)=(100%:71)*40=56,34%.