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Chloride, bromide and iodide salts are generally soluble. Which cations are the listed exceptions?
ACalcium, barium and strontium
BSilver, mercury(I) and lead(II)
CSodium, potassium and ammonium
DIron(III), aluminium and zinc
Answer & Solution
Correct answer: B. Silver, mercury(I) and lead(II)
1. The guidelines call compounds containing Cl-, Br- and I- soluble.
2. The exception row for that entry names halides of Ag+, Hg2 2+ and Pb2+.
3. This is why PbI2 comes down as a solid when KI meets Pb(NO3)2.
4. It is also why AgCl precipitates when chloride meets silver ions.
5. Calcium, barium and strontium are exceptions for sulfates, not for chlorides or iodides.
6. Sodium, potassium and ammonium salts carry no exceptions at all.
7. So the halide exceptions are silver, mercury(I) and lead(II).
_Source: OpenStax Chemistry (CC BY 4.0), Ch 4 "Stoichiometry of Chemical Reactions", section 4.2 Classifying Chemical Reactions_
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