Name: __________________________
Raw Data for Experiment 36 (Make Up)
Below the line below is a description of what a hypothetical student did and observed during the course
of testing her unknown solution during Experiment 36. In addition to creating a flow chart on the
report form for this experiment (the flow chart should correspond only to the observations written
about below), and stating on the report form which cations you believe are present in this unknown
solution, print out this page and do the following:
a) Underline each observation which specifically indicates the presence of a Group-I cation, and state
which cation it identifies. Note that there may (or may not) be more than one such observation, and
if that is the case for a given cation, you should underline (and state the cation for) each. (Note that
there should not be more than two specific observations for any one cation).
b) For each cation that you conclude is not in the unknown, underline the part of the prose below that
makes you believe the cation is not present and state the cation. Also write in the margin what
should have been observed had the ion been present. (In other words, state the observation(s) that
should have been expected in the “known solution” that were not seen during the experiments with
the unknown solution.)
NOTE: You do NOT need to put down any observations in the space on the report form that asks for
observations.
-----------------------------------1 mL of unknown solution, which was colorless, was put into a medium sized test tube. 2 drops of 6 M
HCl(aq) was added and a white precipitate was observed. The contents of the tube were mixed with a
glass stirring rod, and the mixture was centrifuged. One more drop of 6 M HCl(aq) was added to the
tube, and no additional precipitate was observed to form where the drop made contact with the
colorless solution. The supernatant liquid was decanted into a separate tube. 2 mL of deionized water
was added to the precipitate. The precipitate was broken up into tiny pieces with a glass stirring rod,
the mixture was stirred well, and then the mixture was centrifuged. The colorless supernatant was
discarded. 2 mL of deionized water was added to the precipitate, the precipitate was broken up into
tiny pieces with a stirring rod, the mixture was stirred well, and then the tube was placed into a 250-mL
beaker half filled with boiling water sitting on a hot plate. The tube was left in the boiling water bath for
about two minutes, during which time it was stirred occasionally. The tube, whose contents still
appeared cloudy and white, was carefully removed with a test tube clamp, and immediately transferred
into a centrifuge for centrifuging. Immediately after the centrifuge stopped spinning, the tube—which
contained a white pellet / precipitate at the bottom—was removed with the test tube clamp and the
colorless solution decanted into a clean test tube. The tube with the white precipitate was saved for
later.
One drop of 6 M acetic acid and three drops of 0.1 M K2CrO4(aq) were added to the solution from the
prior paragraph. A yellow solution (tube contents were clear but yellow) resulted.
1 mL of 6 M NH3(aq) was added to the tube with the white precipitate from the end of paragraph one,
the mixture was stirred thoroughly, and a grayish precipitate was observed. The mixture was
centrifuged, and the colorless solution was decanted into a clean tube. About 1 mL of 6 M HNO3(aq)
was added to this tube and the contents stirred well. The contents remained a clear and colorless
solution. When the stirring rod used to stir this mixture was touched to a piece of blue litmus paper, the
litmus turned red.