What result might you get if some or silver or lead ions remained soluble when y

Question

What result might you get if some or silver or lead ions remained soluble when you separated group two supernatant solution - in laler Steps? (Where would It go, what might happen?) What are the letters or numbers of the steps in the procedure for the general unknown that seem to repeat themselves in the group II section? these are a check that a acid insoluble sulfides have been precipitated? (Group II) In group II, what is the purpose of matching the solution's methyl violet color to the green color the indicator takes when spotted with 0.3M HCI?

Explanation / Answer

1) if not precipitated properly as chlorides,on addition of 6M HCl,group 1 cations -Ag+ ,Pb2+ and Hg2+ may remain in group 2 supernatant solution and later on get precipitated with group 2 cations as Ag2S,PbS and HgS on addition of H2S gas.Though Pb2+ may be separated again from the mixture of precipitate in the form of PbNO3 in solution on acidification with conc HNO3 followed by addition of sulfuric acid to precipitate it as PbSO4.Further addition of lead acetate dissolves insoluble PbSO4 as Pb(CH3COO)2.When Potassium chromate KCrO4 is added PbCrO4 (yellow ppt) confirms the presence of Pb2+ in group 2.However AgS and HgS may remain in solution when NH3 is added to separate group 2 cations in the form of soluble[ Ag(NH3)2]+ ,[Hg(NH3)2]2+ and interfere in group 3 analysis.

2) step 1The supernatant solution obtained from group 1 analysis is made basic by adding 6M NH3 solution.

step2 add 2M Hcl until the pH is between 2 and 3.(compare the color of the solution by adding an indicator like methyl orange)

add thioacetamide solution and dilute with water.Recheck pH with pH strips until it is 0.5.Heat for 5 minutes.Any group 2 sulfide present will precipitate out.group 2 sulphides precipitates at pH 0.5-1.0 while group 3 sulfides precipitates in basic conditions.(more soluble sulfides)

3)To check if the pH is in the range of 0.5-1.0 for precipitation of group 2 sulfides

2) th

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