Consider the two different unknowns, one labeled (a) and one labeled (b), each c
ID: 1020094 • Letter: C
Question
Consider the two different unknowns, one labeled (a) and one labeled (b), each contains ONLY ONE of the two cations/precipitates listed.
Give a single CHEMICAL reagent that would allow you distinguish which cation/precipitate is in the unknown.
1) Contains either Mg+ (aq) or Zn +2 (aq)....
a) Add the following reagent:
b) Expected observation for Mg+?
c) Expected observation for Zn +2?
2) Contains either AgCl(s) or PbCl(s)
a) Add the following reagent:
b) Expected observation for AgCl?
c) Expected observation for PbCl2?
Explanation / Answer
1) Reagent NaOH that will precipitate out both Zn2+ and Mg2+
Mg2+(aq) + 2OH–(aq) ==> Mg(OH)2(s)gives a white precipitate
Zn2+(aq) + 2OH–(aq) ==> Zn(OH)2(s)a white precipitate formed
2) Reagent HCl that will precipitate out both Ag+ and Pb2+
Ag+(aq) + Cl–(aq) ==> AgCl(s)gives a white precipitate
Pb2+(aq) + 2Cl–(aq) ==> PbCl2(s)a white precipitate formed