A mixture of solid chlorides was known to contain some or all of the following cations: Ag+, Al3+, Cr3+, ca2+, and/or Zn2+. A student performed the following steps: 1. Water was added to the solid and the mixture was stirred well. After several minutes, some of the solid did not dissolve. The mixture was centrifuged and the supernatant was decanted from the solid (solution A).
2. NH4Cl(aq) was added to solution A followed by NH3(aq) until the solution was basic to litmus. A gray-green precipitate was formed. The mixture was centrifuged and the supernatant (solution B) was decanted. The solid dissolved in NaOH(aq) and H2O2(aq) to form a colorless solution. The solution was heated to dryness to remove the H2O2 and the solid was redissolved in acid. When the solution was made basic with ammonia, a transparent precipitate was formed. The addition of Bacly to the supernatant of the solution containing the transparent precipitate produced no reaction.
3. (NH4)2C204(aq) was added to solution B, and no precipitate formed (solution C).
4. NaOH(aq) was added slowly to solution with constant stirring. A precipitate formed but then dissolved. When a few drops of K4Fe(CN)6(aq) were added to this solution, a grey-blue precipitate formed.
For each of the five cations listed on the first line of this question, identify whether it was definitely present, definitely absent or its presence or absence was unable to be determined in the original solid, after the procedures given above. A confirmatory test for each cation is not required for a determination of definitely present to be made.
A. Present
B. Unable to determine if this ion is present
C. Not Present
Ag*
Al3+
Ca2+
Zn2+