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Experiment 4: Identification of Unknown through Qualitative Analysis
I
...
Standards were used in numerous tests and the unknown was also
subjected to these tests
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II
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The possible categories of the unknown are alkane, alkene, alkyl halide, alcohol, phenol, amine,
aldehyde, ketone, and carboxylic acid
...
These functional groups have their own combinations of solubility and reactivity that
allows them to be distinguished from each other
...
The following tests were Ignition test,
Baeyer test, Hydroxamic test, Lucas reagent test, Chromic acid test, 2,4-DNPH test, Iron
Chloride test, Iodofom test, and Tollen’s test
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A negative to the
Baeyer’s test indicates that there are no alkenes and alkynes present
...
The Hydroxamic acid test is for determining the presence of esters
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The Lucas Test,
Chromic acid test and Iodoform test are used to determine the presence of secondary and tertiary
alcohols and aldehydes
...
Baeyer test was performed by adding a few drops of KMnO4
solution in water and a few drops of the sample; if a precipitate is formed, then it yields a
positive test
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For Hydroxamic test, 1mL 0
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0
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After heating, 2M HCl was added dropwise until it became acidic
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2 drops of 3% ferric
chloride was then added; if solution turns purple, then it yields positive
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Iron (III) Chloride test was performed by dissolving a drop of the
sample in 1mL water and 5 drops of 2% aqueous Iron (III) Chloride; the solution should not
remain yellow-colored to be a positive test
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If a precipitate forms after agitating then it’s a positive test
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The Tollen’s test is performed by adding a drop of
the sample into 2mL Tollen’s reagent, mix and then heat gently for 15 minutes; a silver mirror
should form to be a positive test
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Results and Discussions
Table 1:
Sample
H2 O

NaOH

5% NaHCO3

5% HCl

Benzene
Cyclohexene
T-butanol
Isopropanol
Acetone
Ethanol
Toulene
Unknown

+
+
+
+
+
-

+
~
+
+
+

+
+
+
+

~
+
~
+
+
+

Table 2:
Sample

Ignition Baeyer Hydrox- Lucas Chromic 2,4
Iron
Iodoform Tollens
amic
Acid
DNPH Chloride
Benzene
Yellow,
+
+
+
+
+
sooty
Cyclohexene Yellow,
sooty
T-butanol
Yellow,
+
nonsooty
Isopropanol
Yellow,
+
+
nonsooty
Acetone
Yellow,
+
+
nonsooty
Ethanol
Yellow,
+
+
nonsooty
Toulene
Yellow,
sooty
Unknown
Yellow,
+
+
nonsooty
The unknown is believed to be an alcohol (ethanol) because it yielded positive in the
chromic acid test and the iodoform test
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Moreover, ignition test performed yielded a yellow, non-sooty flame
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IV
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These are tests that determine the presence of alcohols and aldehydes
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IV
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Given an alkane, 3o alcohol, alkyl halide, and alkene, which of the four compounds
would yield positive to the following tests:

H2SO4

Br2/CCL4 KMnO4 CrO3 Alcoholic Compound
AgNO3
Insoluble
Alkanes
Soluble
Alcohol
Insouble
+
Alkyl
Soluble
+
+
Alkene
2
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2-bromoethanol and 1,2-dibromoethane
- Chromic Test for 2-bromoethanol; it’s positive if it becomes blue-green
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b
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- Bromine-water test for 1-hexene; yields positive if reddish color disappears
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1-chloro-2-methyl-2-propanol and 1,2-dichloro-2-methylpropane
- Lucas test for 1-chloro-2-methyl-2-propanol; yields positive if a 2nd phase forms
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d
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- Silver Nitrate Test for butane; it yields positve if silver precipitate forms
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References
[1] Hagen, J
...
Supplement to Laboratory Manual (Fall 2009) Chemical Tests
accessed July 23, 2013 from <  http://plsk7
...
net/compounds/chemical_tests

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