The sodium fusion extract (NaX) when acidified with nitric acid (HNO3) and then treated with silver nitrate (AgNO3) gives a white curdy precipitate. Then choose the correct statement(s) :
A
X is chlorine
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B
X is bromine.
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C
Precipitate formed is soluble in NH4OH
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D
Precipitate formed is insoluble in NH4OH
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Solution
The correct option is C Precipitate formed is soluble in NH4OH Test for halogens :
The sodium fusion extract having NaX is acidified with nitric acid (HNO3) and then treated with silver nitrate (AgNO3)
Case 1 :
White curdy precipitate soluble in NH4OH indicates presence of Cl NaCl+AgNO3→AgClWhite ppt.↓+NaNO3 AgCl dissolves in ammonium hydroxide (NH4OH)
Case 2:
Pale yellow precipitate sparingly soluble in NH4OH indicates presence of Br NaBr+AgNO3→AgBrPale yellow ppt.↓+NaNO3 AgBr is sparingly soluble in ammonium hydroxide (NH4OH).
Case 3 :
Yellow precipitate insoluble in NH4OH solution indicates presence of I NaI+AgNO3→AgIYellow ppt.↓+NaNO3 AgI is insoluble in ammonium hydroxide (NH4OH)
The presence of nitrogen or sulphur interferes in the detection of halogens.These atoms should be removed by boiling the sodium fusion extract with concentrated nitric acid to decompose the cyanide or sulphide.