Em tham khảo nha:
\(\begin{array}{l}
3)\\
2KMn{O_4} \xrightarrow{t^0} {K_2}Mn{O_4} + Mn{O_2} + {O_2}\\
2Ca + {O_2} \xrightarrow{t^0} 2CaO\\
CaO + {H_2}O \to Ca{(OH)_2}\\
4)\\
CTHH:N{a_x}{O_y}{H_z}\\
x:y:z = \dfrac{{11,5}}{{23}}:\dfrac{8}{{16}}:\dfrac{{0,5}}{1} = 1:1:1\\
\Rightarrow CTHH:NaOH\\
5)\\
A{l_2}{O_3} + 3{H_2}S{O_4} \to A{l_2}{(S{O_4})_3} + 3{H_2}O\\
n{H_2}S{O_4} = \dfrac{{58,8}}{{98}} = 0,6\,mol\\
nA{l_2}{O_3} = \dfrac{{61,2}}{{102}} = 0,6\,mol\\
\dfrac{{0,6}}{1} > \dfrac{{0,6}}{3} \Rightarrow \\
nA{l_2}{O_3} = 0,6 - 0,2 = 0,4\,mol\\
mA{l_2}{O_3} = 0,4 \times 102 = 40,8g
\end{array}\)
