A student was testing an unknown cation solution. Based on the three cations use
ID: 515610 • Letter: A
Question
A student was testing an unknown cation solution. Based on the three cations used in this experiment, answer the following: a. The student added HCl and a precipitate formed. Which cation(s), discussed in this experiment, could be in this sample? List all cations. b. Continuing with the same the student next heated the solution with the precipitate and all of the precipitate dissolved. Based on your answer(s) in part "a", indicate which of these cations must be present, which of these cations must be absent, which cation may be present (inconclusive). cation(s) present _____ cation(s) absent _____ cation (s) that might (may or may not) be present (inconclusive) _____ While performing the ammonium ion test on the known solution (that contains all three of the cations), the student noticed that a lot of precipitate formed. Write the formula(s) for the precipitate(s). Ammonium hydroxide is often referred to as "ammonia water". Write the chemical equation showing that ammonium hydroxide, and ammonia dissolved in water, are two sides of an equilibrium. Write two different balanced chemical equations showing how the silver chloride precipitate can be dissolved.Explanation / Answer
Identification of cations in solution
1. Addition of HCl formed precipitate
a. the ions present could be Ag+, Pb2+, Tl+ or Hg+ all belonging to Group I cations
b. heating dissolved precipitate
Pb2+ is present. PbCl2 dissolves on heating in water
Cation present : Pb2+
cation absent : Ag+, Hg+, Tl+
2. when testing for NH4+, the three cations which form precipitate are,
Cu2+ forms Cu(OH)2 (blue ppt)
Fe2+ forms Fe(OH)2 (green ppt)
Fe3+ forms Fe(OH)3 (brown ppt)
3. NH4OH as NH3 source
NH4OH <==> NH3 + H2O
4. AgCl precipiate dissolution,
AgCl(s) + Cl-(aq) --> AgCl2-(soluble)
AgCl(s) + 2NH3(aq) ---> [Ag(NH3)2]+(soluble) + Cl-(aq)
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.