$X$ is a salt of one of the halogens chlorine, bromine, iodine or astatine (proton number $85$). The reaction scheme illustrates a sequence of reactions that begins with a solution of $X$ as the starting reagent. $X \xrightarrow[\text{AgNO}_3(aq)]{\text{HNO}_3(aq)} \text{a precipitate} \xrightarrow[\text{excess}]{\text{dilute } \text{NH}_3(aq)} \text{a colourless solution} \xrightarrow[\text{excess}]{\text{HNO}_3(aq)} \text{a precipitate}$ What could $X$ be?
- Asodium chloride
- Bsodium bromide
- Cpotassium iodide
- Dpotassium astatide