Question

Sodium fusion extract of halogen compound is acidified with nitric acid and reacted with silver nitrate $\left(AgN{O}_3\right)$ to give precipitate.
Which of the following is true regarding the above statement?

• A. White precipitate indicates $Cl$
• B. Black precipitate indicates $Br$
• C. Orange precipitate insoluble in $N{H}_{4}OH$ indicates $I$
• D. Yellow precipitate insoluble in $N{H}_{4}OH$ indicates $Cl$

Answer 1

The correct option is A White precipitate indicates $Cl$

Test for halogens :
The sodium fusion extract having $NaX$ is acidified with nitric acid $\left(HN{O}_3\right)$ and then treated with silver nitrate $\left(AgN{O}_3\right)$
Case 1 :
White curdy precipitate soluble in $N{H}_{4}OH$ indicates presence of $Cl$
$NaCl+AgN{O}_3\to \underset{\text{White ppt.}}{AgCl}\downarrow +NaN{O}_3$
$AgCl$ dissolves in ammonium hydroxide $\left(N{H}_{4}OH\right)$

Case 2:
Pale yellow precipitate sparingly soluble in $N{H}_{4}OH$ indicates presence of $Br$
$NaBr+AgN{O}_3\to \underset{\text{Pale yellow ppt.}}{AgBr}\downarrow +NaN{O}_3$
$AgBr$ is sparingly soluble in ammonium hydroxide $\left(N{H}_{4}OH\right)$.

Case 3 :
Yellow precipitate insoluble in $N{H}_{4}OH$ solution indicates presence of $I$
$NaI+AgN{O}_3\to \underset{\text{Yellow ppt.}}{AgI}\downarrow +NaN{O}_3$
$AgI$ is insoluble in ammonium hydroxide $\left(N{H}_{4}OH\right)$
Thus, statement (a) is true.