Осуществите цепочку превращений:
Al - AlCl3 - Al(OH)3 - Al2O3 - Al2(SO4)3
↓
AlBr3 - AgBr

2Al + 3Cl2 = 2AlCl3

AlCl3 + 3H2O = Al(OH)3 + 3HCl

2Al(OH)3 + Cr2O3 = 2Cr(OH)3 + Al2O3

Al2O3 + 3H2SO4 = Al2(SO4)3 + 3H2O

Al2(SO4)3 + 2CrBr3 = Cr2(SO4)3 + 2AlBr3

AlBr3 + 3AgNO3 = Al(NO3)3 + 3AgBr