Em tham khảo nha :
\(\begin{array}{l}
3)\\
{n_{S{O_2}}} = \dfrac{{4,49}}{{22,4}} = 0,2mol\\
Ca{(OH)_2} + S{O_2} \to CaS{O_3} + {H_2}O\\
{n_{Ca{{(OH)}_2}}} = {n_{S{O_2}}} = 0,2mol\\
{m_{Ca{{(OH)}_2}}} = 0,2 \times 74 = 14,8g\\
C{\% _{Ca{{(OH)}_2}}} = \dfrac{{14,8}}{{200}} \times 100\% = 7,4\% \\
b)\\
{n_{CaS{O_3}}} = {n_{S{O_2}}} = 0,2mol\\
{m_{CaS{O_3}}} = 0,2 \times 120 = 24g
\end{array}\)