B. Multi-ion mixtures 1. Suppose that Lebowski student had a solution that may c
ID: 482894 • Letter: B
Question
B. Multi-ion mixtures 1. Suppose that Lebowski student had a solution that may contain any or all of the following cations: Ag Pb Ban' Ni2* in his UNKNOWN mixture. Lebowski adds HCI to the solution and a 2+ precipitate forms. He then removes the precipitate and adds NH 3 al to the supernatant until the solution is basic, no solid forms. After making the supernatant basic, K2Croa is then added and a precipitate forms. From what you know about how these ions react, which ions are present in Lebowski's unknown? Indicate with a "yes no", or "possibly" then explain. (8 marks) a. was Ag+ present in the unknown sample How do you know? b. Was Pb2+ present in the unknown sample? How do you know? c. Was Ba2+ present in the unknown sample? How do you know?Explanation / Answer
Qualitative analysis of cations
a. Ag+ present : Possibly
Formation of precipitate with HCl could be due to presence of either Ag+ or Pb2+ in solution. Both are group I cations.
b. Pb2+ present : possibly
Formation of precipitate with HCl could be due to presence of either Ag+ or Pb2+ in solution. Both are group I cations.
c. Ba2+ Present : Yes
Formation of precipitate with K2CrO4 as Ba(CrO4)2 confirms the presence of Ba2+ cation in the unknown.
d. Ni2+ present : No
Absence of any precipitate with NH3 confirms Ni2+ is absent in the unknown
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