Cation Analysis Formal

.docx

School

Indiana University, Purdue University, Indianapolis *

*We aren’t endorsed by this school

Course

126

Subject

Chemistry

Date

Feb 20, 2024

Type

docx

Pages

8

Uploaded by faith.bittner

Cation Analysis Faith Bittner Jimmy O'Keefe C126 Experimental Chemistry II Section 25032 April 10, 2023 Introduction The world of chemistry is heavily dependent on qualitative analyses, or numerical data and its interpretation. This includes volumes taken to reach an endpoint in a titration, or the amount of heat, in degrees, needed to reach a boiling point. However, there is another side of chemistry where numerical data is not present. This is known as a qualitative analysis. Rather than determining quantities of substances, the goal is to identify what substances are in an unknown sample. This can be achieved through a variety of tests and methods, which can include flame tests, spot tests, and separations. Separations usually involve precipitation reactions. Flame tests and spot tests help to confirm the presence of the unknown. A flame test involves a molecule containing a metal ion to be placed in a flame. Different metals will flicker different colors and can be used as an identification method. However, there is a lot of room for contamination with this method. Spot tests are when the unknown compound is reacted with a known reagent. A precipitate, color change, or nothing will result. The problem with spot tests is if more than one ion in the unknown reacts with the known reagent. Therefore, separations are the best method to use when there are more at least two unknown cations present. Various precipitating reagents can be used to precipitate certain ions out of a solution. Then, a centrifuge can separate the precipitate. Furthermore, precipitate-dissolving reagents are used to dissolve the precipitate or the supernatant. There are times where an unknown substance will be encountered, and it will need to be examined to discover its contents. A prime example of this is in forensic science. There are always questioned substances that are found at crime scenes and breaking these into their components can help gain understanding of what the scientists are dealing with. In addition, it can also lead to solving the case by identifying a crucial piece of evidence and connecting it with a suspect.
The purpose of this lab was to develop a scheme that could separate and identify a compound composed of unknown metal ions, which could have included silver (Ag + ), iron (Fe 2+ ), nickel (Ni 2+ ), lead (Pb 2+ ), and potassium (K + ). Experimental Procedure/Data and Calculations The procedure for this experiment consisted of two parts: testing the known metal cations and determining the metal cations present in an unknown solution. The first test conducted was the spot test. One drop of each of the metal ion solutions was added to one drop of each of the spot test reagents. The spot test reagents were K 2 CrO 4 , K 4 [Fe(CN) 6 ], NH 3 , and dimethylglyoxime. After initial observations were recorded, a stirring rod was used, and additional observations were made. The data from this test can be found in Table 1 of the Results section. The second test performed was the separation method using precipitation reactions. A few drops of each metal ion solution were added to a test tube with a few drops of each precipitating reagent. The precipitating reagents were 6M HCl and 6 M NH 3 . If a precipitate formed, then two additional samples were created. Each precipitate sample was centrifuged and decanted. Then, the solubility of the precipitate was tested with each precipitate-dissolving reagent. The precipitate-dissolving reagents included 6 M NH 3 , 6 M HNO 3 , and hot DI water. Table 2 of the Results section contains the precipitating reagents data, while Table 3 displays the results with the precipitate-dissolving reagents. The third test was the flame test. A wire loop was dipped into the metal ion solution. The wire was then placed into a Bunsen burner flame. The color change of the flame was observed for each solution. The observations of this part can be found in Table 4 of the Results section. From the observations and data of the known metal cations in each test, a flow chart scheme was developed. This is labeled as Figure 1. Part 2 of this experiment involved using this analysis scheme on an unknown solution that contained any combination of the five metal cations. The procedure in the aforementioned paragraph, along with the flow chart, was tested using the unknown. Based on observations of the unknown with the different tests, a conclusion was able to be made about which cations were present. The unknown used in the experiment was #74.
Figure 1 No calculations were performed in this experiment. Results and Discussion The spot test reagents had a variety of results, which included color changes, precipitate formation, and even nothing at all (indicated by NR). Gaining a reference of how the known solutions react with the reagents was important when it came to the unknown solution. The result of the unknown cation with the reagents was able to be compared to the spot test in Part 1 where every reagent used was known. This test was conclusive. Table 1: Spot Test K 2 CrO 4 K 4 [Fe(CN) 6 ] NH 3 Dimethylglyoxime Pb 2+ yellow with ppt after stirring: ppt sticks together yellow, no ppt white ppt after stirring: ppt spread out NR
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
  • Access to all documents
  • Unlimited textbook solutions
  • 24/7 expert homework help
Recommended textbooks for you
Text book image
Chemistry: The Molecular Science
Chemistry
ISBN:9781285199047
Author:John W. Moore, Conrad L. Stanitski
Publisher:Cengage Learning
Text book image
Chemistry & Chemical Reactivity
Chemistry
ISBN:9781337399074
Author:John C. Kotz, Paul M. Treichel, John Townsend, David Treichel
Publisher:Cengage Learning
Text book image
Chemistry & Chemical Reactivity
Chemistry
ISBN:9781133949640
Author:John C. Kotz, Paul M. Treichel, John Townsend, David Treichel
Publisher:Cengage Learning
Text book image
Chemistry for Engineering Students
Chemistry
ISBN:9781337398909
Author:Lawrence S. Brown, Tom Holme
Publisher:Cengage Learning
Text book image
Chemistry: Principles and Practice
Chemistry
ISBN:9780534420123
Author:Daniel L. Reger, Scott R. Goode, David W. Ball, Edward Mercer
Publisher:Cengage Learning
Text book image
General Chemistry - Standalone book (MindTap Cour...
Chemistry
ISBN:9781305580343
Author:Steven D. Gammon, Ebbing, Darrell Ebbing, Steven D., Darrell; Gammon, Darrell Ebbing; Steven D. Gammon, Darrell D.; Gammon, Ebbing; Steven D. Gammon; Darrell
Publisher:Cengage Learning
SEE MORE TEXTBOOKS
Recommended textbooks for you
Text book image
Chemistry: The Molecular Science
Chemistry
ISBN:9781285199047
Author:John W. Moore, Conrad L. Stanitski
Publisher:Cengage Learning
Text book image
Chemistry & Chemical Reactivity
Chemistry
ISBN:9781337399074
Author:John C. Kotz, Paul M. Treichel, John Townsend, David Treichel
Publisher:Cengage Learning
Text book image
Chemistry & Chemical Reactivity
Chemistry
ISBN:9781133949640
Author:John C. Kotz, Paul M. Treichel, John Townsend, David Treichel
Publisher:Cengage Learning
Text book image
Chemistry for Engineering Students
Chemistry
ISBN:9781337398909
Author:Lawrence S. Brown, Tom Holme
Publisher:Cengage Learning
Text book image
Chemistry: Principles and Practice
Chemistry
ISBN:9780534420123
Author:Daniel L. Reger, Scott R. Goode, David W. Ball, Edward Mercer
Publisher:Cengage Learning
Text book image
General Chemistry - Standalone book (MindTap Cour...
Chemistry
ISBN:9781305580343
Author:Steven D. Gammon, Ebbing, Darrell Ebbing, Steven D., Darrell; Gammon, Darrell Ebbing; Steven D. Gammon, Darrell D.; Gammon, Ebbing; Steven D. Gammon; Darrell
Publisher:Cengage Learning
SEE MORE TEXTBOOKS