This section contains multiple choice questions. Each question has 4 choices (a), (b), (c) and (d), out of which ONLY ONE is correct. When Lassaigne's solution is treated with dil.HNO, and \(\mathrm{AgNO}_{3}\), a white precipitate soluble in ammonium hydroxide shows the presence of (a) chlorine (b) bromine (c) sulphur (d) nitrogen

We are given that Lassaigne's solution is treated with dilute HNO and \(\mathrm{AgNO}_{3}\), and this results in a white precipitate that is soluble in ammonium hydroxide.

We need to find out which element forms a white precipitate with these reagents that is soluble in ammonium hydroxide. Let's analyze the reactions for each of the given elements: (a) Chlorine: When treated with \(\mathrm{AgNO}_{3}\), chlorine forms \(\mathrm{AgCl}\), which is a white precipitate. Moreover, \(\mathrm{AgCl}\) is soluble in ammonium hydroxide. So, chlorine is a possible answer. (b) Bromine: In the presence of \(\mathrm{AgNO}_{3}\), bromine forms \(\mathrm{AgBr}\), which is a pale yellow precipitate. Since the precipitate should be white, bromine can be ruled out. (c) Sulphur: Though sulphur reacts with \(\mathrm{AgNO}_{3}\) to give a white precipitate of \(\mathrm{Ag}_{2}\mathrm{S}\), it is insoluble in ammonium hydroxide. So, sulphur can be ruled out. (d) Nitrogen: Nitrogen doesn't form a white precipitate with \(\mathrm{AgNO}_{3}\). So, nitrogen can be ruled out.

From the above analysis, we can conclude that chlorine is the only element that forms a white precipitate that is soluble in ammonium hydroxide when treated with dilute HNO and \(\mathrm{AgNO}_{3}\). Therefore, the correct answer is (a) chlorine.