Judith added HC1 solution to her Group A unknown solution and the solution immed
ID: 480064 • Letter: J
Question
Judith added HC1 solution to her Group A unknown solution and the solution immediately clouded up with white ppt. She centrifuged and discarded the supernatant liquid. She then added some hot water to the ppt. in the tt., stirred well and quickly poured the hot mixture onto a pre heated filter. She collected the filtrate in a clean tt. and set it aside. White ppt. remained on the filter. She added several drops of ammonia solution to the ppt. that remained on the filter. It did not change noticeably. She collected the ammoniacal filtrate. At first, it was cloudy. But when she made it acidic with a few drops of nitric acid solution it cleared up and remained clear. She added a few drops of potassium chromate solution to the filtrate she had set aside and it immediately clouded up with yellow ppt. a) What Group A ions were present______, absent_______, in doubt_______? b) Give your reasons for each of your responses to a). c) What was the solid material remaining on the filter after she added ammonia?_________ d) What could have caused the ammoniacal filtrate to be cloudy?Explanation / Answer
A) Based on the given information we conclude that the cation is Pb2+ .
B) Lead ion can form PbCl2 with dil. HCl as a white cloudy precipitate.
c) PbCl2 + NH3 • H2O = PbOHCl + NH4Cl
The precipitate must be Pb(OH)Cl.
d) Because of the formation of the above mixture, it forms a turbidity in ammonical filtrate.
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