Em tham khảo nha :
\(\begin{array}{l}
a)\\
{n_{A{l_2}{{(S{O_4})}_3}}} = \frac{{85,5}}{{342}} = 0,25mol\\
b)\\
{n_{{N_2}}} = \dfrac{{{N_{{N_2}}}}}{{{N_A}}} = \dfrac{{4,8 \times {{10}^{26}}}}{{6 \times {{10}^{23}}}} = 800mol\\
c)\\
{n_{F{e_3}{O_4}}} = \dfrac{{{N_{F{e_3}{O_4}}}}}{{{N_A}}} = \dfrac{{1,5 \times {{10}^{22}}}}{{6 \times {{10}^{23}}}} = 0,025mol\\
d)\\
{n_{{H_2}}} = \dfrac{V}{{22,4}} = \frac{{3,56}}{{22,4}} = 0,1589mol\\
e)\\
{n_{{N_2}}} = \dfrac{{0,168}}{{22,4}} = 0,0075mol\\
f)\\
{D_{{H_2}O}} = 1g/ml\\
{m_{{H_2}O}} = 720g\\
{n_{{H_2}O}} = \dfrac{{720}}{{18}} = 40mol\\
g)\\
{V_{{C_2}{H_5}OH}} = 0,115{m^3} = 115d{m^3} = 115ml\\
{m_{{C_2}{H_5}OH}} = 115 \times 0,8 = 92g\\
{n_{{C_2}{H_5}OH}} = \dfrac{{92}}{{46}} = 2mol
\end{array}\)