Em tham khảo nha:
\(\begin{array}{l}
a)\\
*Zn{(OH)_2}\\
\% {m_{Zn}} = \dfrac{{65}}{{99}} \times 100\% = 65,66\% \\
\% {m_O} = \dfrac{{16 \times 2}}{{99}} \times 100\% = 32,32\% \\
\% {m_H} = 100 - 65,66 - 32,32 = 2,02\% \\
*N{a_2}O\\
\% {m_{Na}} = \dfrac{{23 \times 2}}{{62}} \times 100\% = 74,19\% \\
\% {m_O} = 100 - 74,19 = 25,81\% \\
*CaC{O_3}\\
\% {m_{Ca}} = \dfrac{{40}}{{100}} \times 100\% = 40\% \\
\% {m_C} = \dfrac{{12}}{{100}} \times 100\% = 12\% \\
\% {m_O} = 100 - 40 - 12 = 48\% \\
b)\\
{M_A} = 8 \times 2 = 16\,dvC\\
{m_C} = 75\% \times 16 = 12g\\
{m_H} = 16 - 12 = 4g\\
{n_C} = \dfrac{{12}}{{12}} = 1\,mol\\
{n_H} = \dfrac{4}{1} = 4\,mol\\
{n_C}:{n_H} = 1:4 \Rightarrow CTHH:C{H_4}\\
c)\\
CTHH:F{e_x}{S_y}{O_z}\\
x:y:z = \dfrac{{28}}{{56}}:\dfrac{{24}}{{32}}:\dfrac{{48}}{{16}} = 0,5:0,75:3 = 2:3:12\\
\Rightarrow CTHH:F{e_2}{(S{O_4})_3}
\end{array}\)