\(PTK_A=5\left(64+16\right)=5\left(80\right)=400\) đvC
Ta có: R hóa trị III, nhóm \(SO_4\) hóa trị II
CTTQ: \(R_x\left(SO_4\right)_y\)
Theo quy tắc hóa trị, ta có:
\(\dfrac{x}{y}=\dfrac{II}{III}\Rightarrow x=2;y=3\)
\(\Rightarrow\)CTHH: \(R_2\left(SO_4\right)_3\)
Ta có:
\(PTK_A=2NTK_R+3PTK_{SO_4}=2NTK_R+3\left(32+4\cdot16\right)=2NTK_R+3\left(32+64\right)=2NTK_R+288\)
\(NTK_R=\dfrac{400-288}{2}=56\) đvC (Fe)
Vậy CTHH là \(Fe_2\left(SO_4\right)_3\)