28 POST-LAB QUESTIONS: 1. Write balanced net ionic equations for the following r

Question

28 POST-LAB QUESTIONS: 1. Write balanced net ionic equations for the following reactions: a. The addition of HCl to a solution of Pb" (Step #3) The formation ofa yellowerecipitate in Step #4. (The addition of b. K,CrO, to a solution of Pb) c. The formation of AgCl in Step #5. (Step 1: AgCl dissolves after NH110 added in; step 2: dissolved silver precipitates again after HCI added in) Step 1: Step 2: 2. A solution may contain Pb, Ag', and Hg2. Upon analysis a white precipitate forms on addition of 6M HCI. The precipitate is insoluble in hot water and turns black on addition of 6 M NH,. Which of the ions are present, are absent, or remain undetermined? Justify your answer. Present Absent In Doubt Reason Reason Reason 3. Give the confirmation color for a. AgCI b. Hg Cl e. PbCrO, e. PbCl

Explanation / Answer

Ans no-1

(a) Pb2+(aq) + 2Cl-------> PbCl2 (S)

(b) Pb2+ + K2CrO4 ------>2K++PbCrO4

(c) Step-1 , Ag+ + NH3 +H2O ------> Ag(OH) (s) +  +NH4

Step-2 ,Ag(OH) (s) +HCl ------>AgCl + H2O

Ans no-2

Ans no-3

cation present/absent/doubtful reason Hg2+2 Present due to white color which is converted into black Pb2+ Absent ppt is soluble in hot water Ag+ Absent ppt upon treatment with NH3 turns into colorless solution

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