Testing for chlorides (Cl^-), bromides (Br^-) and iodides (I^-)
3 marks · NormalA student tests three unknown solutions by first adding dilute nitric acid and then silver nitrate solution. The results are:
| Solution | Observation |
|---|---|
| A | white precipitate |
| B | cream precipitate |
| C | no visible change |
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
A: chloride ions (Cl^-), B: bromide ions (Br^-), C: no halide ions present
Must show: A: chloride/Cl^-, B: bromide/Br^-, C: absence of halide ions
Also accept: Use of chemical names (chloride, bromide) or correct formulae (Cl^-, Br^-)
Common mistakes: Swapping which colour matches which ion; Stating 'iodide' instead of 'bromide' for cream; Assuming C contains an ion not tested for
Show mark scheme and worked solution
Marking points
M1 · 1 mark · Identifies chloride ions as responsible for the white precipitate (A).
M1 · 1 mark · Identifies bromide ions as responsible for the cream precipitate (B).
A1 · 1 mark · Correctly states that solution C contains no halide ions (no visible change).
Worked solution
Solution A: White precipitate indicates chloride ions (Cl^-).
Solution B: Cream precipitate indicates bromide ions (Br^-).
Solution C: No visible change means no chloride, bromide or iodide ions present.