Đổi: 54cm=5,4dm

Dài đáy:

22,4 x 2 : 5,4=224/27(dm)

\(PTK_{X_2O_5}=3,55.NTK_{Ca}=3,55.40=142\left(đ.v.C\right)\\ Mà:PTK_{X_2O_5}=2.NTK_X+80\left(đ.v.C\right)\\ \Rightarrow2NTK_X+80=142\\ \Leftrightarrow NTK_X=\dfrac{142-80}{2}=31\left(đ.v.C\right)\\ \Rightarrow X:Photpho\left(P=31\right)\\ \Rightarrow Hợp.chất:P_2O_5\)

Cái này mình đã hỗ trợ nha!

Câu 1:

a)

\(n_{AgNO_3}=0,5.0,1=0,05\left(mol\right)\\ Fe+2AgNO_3\rightarrow Fe\left(NO_3\right)_2+2Ag\\ 0,025......0,05......0,025.....0,05\left(mol\right)\\ m=m_{rắn}=\left(15-0,025.56\right)+0,05.108=19\left(g\right)\)

b) 

\(Fe\left(NO_3\right)_2+2NaOH\rightarrow Fe\left(OH\right)_2\downarrow+2NaNO_3\\ Fe\left(OH\right)_2\underrightarrow{^{to}}FeO+H_2O\\ n_{FeO}=n_{Fe\left(OH\right)_2}=n_{Fe\left(NO_3\right)_2}=0,025\left(mol\right)\\ m_{oxit}=m_r=m_{FeO}=72.0,025=1,8\left(g\right)\)

Câu 2:

a) Na

b) Fe, Al, Mg, Na