A sample which may contain silver, lead or mercury ions or some combination of t

Question

A sample which may contain silver, lead or mercury ions or some combination of these metals is treated with chloride ions, whereupon a white precipitate formed. The solution is heated and the hot solution is filtered. When the filtrate is treated with chromate ions (CrO4^-2), a clear yellow solution results. The remaining white solid in the filter paper has ammonia water poured through it. This dissolves all of the precipitate in the filter paper. The new filtrate is treated with HCl, giving a white precipitate. What metal ion or ions are in the solution? Explain your reasoning.

Explanation / Answer

All silver, lead and mercury give white ppt whe treated with chloride ions.

But when treated with chromate ion, silver and mercury gives yellow solution but lead forms a yellow ppt.

When treated with ammonia solution, silver chloride forms a complex and dissolves in the solution whereas mercury forms a black or grey ppt.

When treated with HCl again, AgCl is formed which is a white ppt.

From this data we can conclude that only Silver ions are present in the solution as there is no yellow ppt with chromate ion(no Pb), no black ppt with ammonia solution(no Hg).

Hence, only silver is present.

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