\(13,\\ PTHH:2Fe\left(OH\right)_3\rightarrow^{t^o}Fe_2O_3+3H_2O\\ \text{Bảo toàn KL: }m_{Fe\left(OH\right)_3}=m_{Fe_2O_3}+m_{H_2}\\ \Rightarrow m_{Fe\left(OH\right)_3\left(\text{p/ứ}\right)}=13,5+40=53,5\left(g\right)\\ \Rightarrow\%_{Fe\left(OH\right)_3\left(\text{phân hủy}\right)}=\dfrac{53,5}{100}\cdot100\%=53,5\%\)