What are the chemical formulas for these

auric sulfate or gold (III) sulfate

and ferrous arsenate or iron (II) arsenate

Au2(SO4)3
Fe3(AsO4)2

You probably know that the sulphate ion is (SO4)^2-, you know that Au is Au^3+ . the pluses and minus' charges must be equal so 2xAu^3+ has 6+ 3 x (SO4)^2- gives 6- balanced!
Now you apply the same logic to iron(II) arsenate

Gold (III) sulfate- [Au(S04)2]1-
Iron (II) arsenate- [Fe(AsO3)]