An analytical chemist at an environmental monitoring station is testing a water sample from a local river near an industrial site. They suspect contamination with iron(II) ions (Fe2+\text{Fe}^{2+}Fe2+). A colleague suggests using a test reagent that forms a distinctive green precipitate when added to iron(II) ions. However, it is known that this same reagent also forms an identical green precipitate when added to nickel(II) ions (Ni2+\text{Ni}^{2+}Ni2+).
Explain why this test reagent is unsuitable for confirming the presence of iron(II) ions in the river sample.
Practise Edexcel GCSE Chemistry Qualitative analysis: tests for ions with exam-style questions for Foundation and Higher tier. 127 questions, matched to the Edexcel GCSE Chemistry (1CH0) specification and written in Paper 1 and Paper 2 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.
