Final answer:
The resulting color of an aqueous solution of NiCl2 is green. The introduction of silver nitrate solution to a colorless salt solution that forms a pale yellow precipitate likely indicates the presence of iodide ions, which react with AgNO3 to form yellow silver iodide.
Step-by-step explanation:
The resulting color of an aqueous solution of NiCl2 is typically green due to the presence of Ni2+ ions in water. When a test tube contains a clear, colourless salt solution, the introduction of silver nitrate solution leading to the formation of a pale yellow precipitate indicates the presence of halide ions. The original salt in the solution reacted with silver nitrate according to the equation: AgNO3(aq) + X−(aq) → AgX(s) + NO3−(aq), where X could be a halogen such as Cl−, Br−, or I−. The pale yellow precipitate suggests that the halide ion was likely I− (iodide), forming silver iodide (AgI), which is known for its yellow color.