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Chemistry Question on Solutions

During the detection of acidic radical present in a salt, a student gets a pale yellow precipitate soluble with difficulty in NH4OH\text{NH}_4\text{OH} solution when sodium carbonate extract was first acidified with dil. HNO3\text{HNO}_3 and then AgNO3\text{AgNO}_3 solution was added. This indicates the presence of:

A

Br−\text{Br}^-

B

CO32−\text{CO}_3^{2-}

C

I−\text{I}^-

D

Cl−\text{Cl}^-

Answer

Br−\text{Br}^-

Explanation

Solution

The reactions with Ag+\text{Ag}^+ ions produce different colored precipitates depending on the halide present:

Ag++I−→AgI(Yellow ppt.)\text{Ag}^+ + \text{I}^- \rightarrow \text{AgI} \quad (\text{Yellow ppt.})

Ag++Cl−→AgCl(White ppt.)\text{Ag}^+ + \text{Cl}^- \rightarrow \text{AgCl} \quad (\text{White ppt.})

Ag++Br−→AgBr(Pale yellow ppt.)\text{Ag}^+ + \text{Br}^- \rightarrow \text{AgBr} \quad (\text{Pale yellow ppt.})

Since a pale yellow precipitate was obtained, it indicates the presence of Br−\text{Br}^- ions.