Qualitative Analysis
Author: Fernando Zacarias
Lab Partner: Nicholas French
Instructor: Steven Brown
Chem 104a-015
Date Completed: March 1, 2005
Date Submitted: March 8, 2005
Abstract:
Ten known ions with equal volume were used in spot tests to determine which would produce precipitates. This established the tests that successfully distinguished the presence of ions in a substance. After categorizing each test and the ions that it would successfully identify, a scheme was then used to expose an unknown mixture to the same tests that therefore eliminated the ions not composing the mixture. The ions that tested positive in the mixture were Ag+, Al3+, Co2+, and Mg2+.
Introduction:
Every existing compound, cations included, has a defined set of characteristics that distinguish it from all other compounds. This is useful in determining the presence of specific cations in a sample. By performing given tests on ten known ions, a scheme is then developed to confirm the presence of ions in other solutions. The results will be recorded from the confirmation tests conducted on each of the ions. This information will later be used to test for the presence of ions in unknown solutions. A control, a mixture of all possibilities, will also be tested.
The presence of an ion will be indicated by precipitation and pH. After the tests that illustrate the presence of specific ions are categorized and determined, corresponding tests will be performed on an unknown mixture to establish the present cations. Confirmation tests will then be conducted to verify the results of the initial experiment, and the four remaining ions will be declared as those composing the mixture.
Results:
Mass of salt for standard solutions:
Name |
M.W. (grams) |
Mass of Salt (grams) |
Aluminum Nitrate |
375.14 |
0.9379 |
Calcium Nitrate |
236.15 |
0.5904 |
Cobalt Nitrate |
291.03 |
0.7276 |
Copper Nitrate |
187.55 |
0.4689 |
Ferric Nitrate |
404.00 |
1.0100 |
Magnesium Nitrate |
256.41 |
0.6410 |
Nickel Nitrate |
290.81 |
0.7270 |
Potassium Nitrate |
101.11 |
0.2523 |
Silver Nitrate |
169.88 |
0.4247 |
Sodium Nitrate |
84.99 |
0.2125 |
Flame Test |
||
Ion |
Observation |
Tested Positive? |
Al3+ |
Orange Flame |
|
Ca2+ |
Sparked |
|
Co2+ |
Orange Flame |
|
Cu2+ |
Green flame, then orange |
|
Fe3+ |
Sparked w/ orange flash |
Positive |
K+ |
Orange flame |
|
Ag+ |
Orange flame |
|
Mg2+ |
Sparked, flashed, orange |
Positive |
Na+ |
Orange flame |
|
Ni2+ |
Sparked w/ orange flame |
Positive |
Blank |
Orange flame |
|
Mix |
Flashed, sparked w/ orange |
Positive |
Nitrosonaphthol |
||
Ion |
Observation |
Tested Positive? |
Al3+ |
Yellow w/ orange precipitate |
|
Ca2+ |
Yellow w/ orange precipitate |
|
Co2+ |
Red w/ orange precipitate |
Positive |
Cu2+ |
Yellow w/ brown precipitate |
Positive |
Fe3+ |
Black precipitate |
Positive |
K+ |
Yellow w/ orange precipitate |
|
Ag+ |
Yellow w/ orange precipitate |
Positive |
Mg2+ |
Yellow w/ orange precipitate |
Positive |
Na+ |
Yellow solution |
|
Ni2+ |
Yellow w/ brown precipitate |
Positive |
Blank |
Yellow |
|
Mix |
Dark Brown solution |
Positive |
Thiocyanate |
||
Ion |
Observation |
Tested Positive? |
Al3+ |
Clear |
|
Ca2+ |
Clear |
|
Co2+ |
Pink |
Positive |
Cu2+ |
Yellow |
Positive |
Fe3+ |
Black |
Positive |
K+ |
Clear |
|
Ag+ |
Opaque White |
Positive |
Mg2+ |
Clear |
|
Na+ |
Clear |
|
Ni2+ |
Clear |
|
Blank |
Clear |
|
Mix |
Dark Red w/ Brown |
Positive |
Four ions determined to be present:
Ag+, Al3+, Co2+, Mg2+
Test |
Ag+ |
Al3+ |
Ca2+ |
Co2+ |
Cu2+ |
Fe3+ |
K+ |
Mg2+ |
Ni2+ |
Alizarian |
|
X |
|
|
X |
X |
|
|
|
Aluminon |
|
X |
|
|
X |
X |
|
|
|
Cinchonine |
X |
|
|
|
X |
X |
|
|
|
DMG |
|
|
|
X |
X |
X |
|
|
X |
Nitro |
X |
|
|
X |
X |
X |
|
|
|
Thiocyanate |
X |
|
|
X |
X |
X |
|
|
|
Given: Fe3+ was not one of the ions used to compose the unknown mixtures.
Discussion:
All results were similar to those produced by the other groups. The only variations existed in the flame test, though these results were not used commonly among the class as a standard for testing the presence of the ions. They were employed however in the ultimate test to distinguish the presence of magnesium or calcium in the unknown sample. These erroneous results can be attributed to the inability to accurately note and observe the colors in the flame produced by the ions.
The spot test techniques proved to be successful in that they agreed with the results that were provided by other groups in the class. This is true for both tests mentioned above, excluding the aforementioned flame test. The successfulness of the spot tests is likely the accurate recording of observations for the ions. For example, noting the change to a red color solution with a precipitate in the Thiocyantate test was indicative of a testing positive.
Scheme 2 was employed to establish which ions composed the unknown mixture. The scheme was reliable in that it eliminated many of the ions that were not present early in the scheme and with minimal possibility for misinterpretation. The scheme did become difficult and inaccurate however when the three remaining ions were tested. There existed no test or means by which to establish the participating ion. The flame test therefore had to be used, as noted above, though the results that were used were inconclusive with other groups. It was successful though in analyzing the remaining mixture for the correct ion, magnesium, which caused the flame to spark.
CHEMISTRY 211 LAB FALL 2004 CHEMICAL INTERACTIONS QUALITATIVE ANALYSIS
CHEMISTRY EXPERIMENT 163 SPOKANE FALLS COMMUNITY COLLEGE QUALITATIVE ANALYSIS
CRITICAL REALISM DIALECTICS AND QUALITATIVE RESEARCH METHODS1 ABSTRACT CRITICAL
Tags: analysis author:, partner, fernando, analysis, qualitative, nicholas, author, french, zacarias