80 CHM-153 Advance Study Assignment NAME DATE QUALITATIVE ANALYSIS OF GROUP I CA

Question

80 CHM-153 Advance Study Assignment NAME DATE QUALITATIVE ANALYSIS OF GROUP I CATIONS 1) After the precipitation of the Group I cations as chlorides by the reaction with HCI, nearly all of the precipitate dissolves in the hot water. Which ion(s) are present? Which ion(s) are absent? 2a) What type of reaction causes the formation of metallic mercury? b) What reagent is responsible for this reaction? 3a) What reagent causes the silver chloride to dissolve into solution? Give the formula of the silver complex that is formed. 3b) What reagent causes the silver chloride precipitate to reform from the aqueous silver complex? Why does this happen?

Explanation / Answer

Q1

in "cold" solution,

AgCl, PbCl2, and Hg2Cl2 are present

if dissolved in hot water...

PbCl2 dissolves --> PB+2 present

All other are present as chloride

Q2

a)

metallic mercury --> we need ammoina:

Hg2Cl2 + 2 NH3 --> Hg (s) + HgNH2Cl(s) + NH4Cl

b)

the reagent responsible is ammonia

3

a

Agcl to dissolve in solution is --> NH3, since it will add

AgCl + NH3 --> Ag(NH3)2+ (aq) + Cl-

b)

NH3 allows this, ammonia

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