CHMY 141 MUSB Identification of Unknown Cations Simulation Qualitative Lab Report

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Laboratory
�
Qualitative Analysis:
Identification of
Unknown CationsSimulation
Objectives
• Explore the solubility properties of salts
•
Examine precipitation reactions
•
Create a flowchart for determining ions present in unknown mixtures
Equipment and Materials
• This worksheet
Introduction
Qualitative analysis is a process used to find information regarding the composition
of different species in a mixture. The analysis does not give us the amount of material
present so it is not as rigorous as a quantitative analysis, but is often easier and faster to
perform. In this lab you will be creating a way to identify the components in a
mixture of aqueous metal ions using data gathered from several qualitative tests.
Since we cannot be in the lab, this experiment will be done for you. Images of the
experiment are included in this handout, and you will need to view video of the lab to
complete the final part of the worksheet.
PARTI
Data Collection
1. Set up a table in a word document for observations similar to the one shown below.
Be sure to make your grids large enough to write in your observations.
2. Following the table, there are pictures of the experiment. In each picture, a
metal cation has been mixed with one of 5 reagents. Record your observations
for each reaction in the table. If no reaction appears to have occurred, write NR.
Chemistry 141 I Experimental Chemistry
TEST
A
l s.
METAL
a 2+
C
2+
Co
2+
Cu
Fe(CN)t
PO/”°
OHNH3
(NH40H)
H+
1. Set up a table in a word document for observations similar to the
one shown above Be sure to make your grids large enough to write
in your observations.
2. Below are pictures of the experiment. In each picture, a metal
cation has been mixed with one of 5 reagents. Record your
observations for each reaction in the table. If no reaction appears
to have occurred, write NR.
zn
2+
Qualitative Analysis: Identification of Unknown Cations I Laboratory 9
Data Analysis
1. Use the observations in your data table to complete the following reactions. If no
reaction was observed, write NR. Assume that precipitates are simple cation:anion
ratios and have a neutral charge. Include any reactions that occur in the data
section of your repor
A.
D. Cu2+
Af3+
A. A1H + Fe(CN\3- ➔
A. Cu2+ + Fe(CN\3- ➔
4
B. A1H
+ PO 3- ➔
B. Cu2+ + PO 3- ➔
C. A1H + OH- ➔
B. Ca2+
A. Ca2+ + Fe(CN\3- ➔
B. Ca + PO – ➔
2+
3
4
C. Ca2+ + OH- ➔
4
C. Cu2+ + OH- ➔
E. Zn2+
A. Zn2+ + Fe(CN\3- ➔
B. Zn2+ + PO 3- ➔
4
C. Zn2+ + OH- ➔
C. Co2+
A. Co2+ + Fe(CN\3- ➔
B. Co2+ + PO 3- ➔
4
C. Co2+ + OH- ➔
2. Next, steps i.-iv. listed below were
completed for each ion.
i. Ten drops of fresh metal cation
solution was placed in a new small
test tube and 4-6 drops of HNO3 was
added acidify the solution. Then 7
drops ofK3Fe(CN\ solution was added
to the test tube. The image to the
right shows the result of these
additions for each metal ion. Use this
information to fill in the flow chart on
page 73. (A video of this reaction is
available online.)
2!J
ii. Then, a fresh 10-drop sample of the
metal cation solutions were transfered
into separate, new test tubes. Eight drops
of NaOH solution was added to each. The
result is shown in the image to the left. Use
this information to fill in the appropriate
part of your flow chart on page 73. (A
video of this reaction is available online.)
If a precipitate formed, the sample was
mixed thoroughly and centrifuged (this
allows us to separate the solid from the
liquid)
iii. After the samples containing the
precipitate finished centrifuging, the
liquid (supernatant)was decanted
(poured off) into a waste beaker. Then,
the solid was washed with ~ 1 mL of
deionized water (using a pipette to break
up any solid and ensure a good wash).
The sample was then centrifuged again,
and the supernatant was carefully
decanted into the waste beaker, making
sure not lose any solid. This wash was
repeated two more times. Once the last
wash was decanted, 10 drops of NH3 was
added and mixed for ~60 seconds. The
samples were then heated for one
minute. The result of this process is shown
in the image to the right. Use this
information to fill in the appropriate
portion of your flow chart on page 73.
iv. The process in step C above was
redone to get a fresh precipitate from the
hydroxide. Each sample was gently
heated for less than 15 seconds. The
result of this process is shown in the image
to the right. This was then centrifuged
and the solid separated from the liquid
(however, this time the supernatant was
recovered for further testing). Use this
information to fill in the appropriate
portion of your flow chart on page 73. (A
video of this reaction is available online.)
72
discard sol’n
pp!
sol’n
Step ii
—–‘———–”
Add NaOH
Al 3+, Cu 2+, Zn 2+,
Co2+, Ca 2+
Step i
♦
add H • 1