A student analyses an unknown anhydrous salt and records the observations in the table below:
| Test | Observation |
|---|---|
| Addition of excess aqueous sodium hydroxide, NaOH(aq)\text{NaOH(aq)}NaOH(aq), dropwise then in excess | A green precipitate forms initially, which dissolves in excess reagent to yield a green solution |
| Addition of acidified aqueous silver nitrate, AgNO3(aq)\text{AgNO}_3\text{(aq)}AgNO3(aq) | A cream precipitate forms |
What is the formula of the salt?
FeBr3\text{FeBr}_3FeBr3
CrCl3\text{CrCl}_3CrCl3
CrBr3\text{CrBr}_3CrBr3
FeBr2\text{FeBr}_2FeBr2