CHEM 1405 - Qualitative Analysis Lab Report
Objective: To test known solutions containing Type I Cations (Ag+1, Hg2+2, and Pb+2) and record observations.
To test unknown solutions containing one or more of the ions above and, by comparing observations with knowns, determine which of the ions are present in the unknown solution.
Background: Qualitative analysis answers the question of whether or not a specific ion is present in a sample, but not how much of the ion is present (quantitative analysis).
In this lab will
perform simulated experiments which will react known solutions containing Type I cations (Ag+1, Hg2+2, and Pb+2) with test solutions. This will involve adding the test solutions to each of the Type I cations individually to observe what reactions occur for each ion. You will then mix the Type I cations together to observe how the three ions react within the mixture. If precipitates formed from the individually known reactions, you will note the color and write the formula for the precipitate formed. These observations will provide the basis for analysis of an unknown solution.
To determine which of the ions are present in the unknown, you will add test solutions to an unknown containing one or more of the ions and look for evidence of reaction (color change, precipitate formation and dissolution of a precipitate). By comparing observations made for knowns to the unknowns solutions, you will determine which ions are present in the unknown sample.
Given that this experiment will be done with a simulation, no PPE is required. Students will still go through the procedure as in lab including centrifugation when needed and even waste disposal. Find the experiment simulation at http://web.mst.edu/~gbert/qual/qual.html.
Practice using the tools in the simulation. Try adding solutions to test tubes and using the centrifuge, litmus paper, decanting, etc. Simply exploring is the best way to learn the simulation, but if you would like the instructions they are on the right hand side of the simulation screen. Once you are comfortable using the simulation tools, proceed with the experiment and complete the data sheet.
1. Place 3 drops of the reagent containing the Ag+ in one test tube, 3 drops of the reagent containing the Hg22+ ion in a second tube, and 3 drops of the reagent containing the Pb2+ ion in a third tube.
2. Add 2 drops of 3M HCl to each tube and observe the precipitates.
3. Centrifuge the tubes. Record observations on your data sheet.
4. Decant and discard the liquid from each tube.
5. Wash the precipitates by adding 2 drops of distilled water to each tube.
6. Centrifuge, decant and discard the supernatant liquids.
7. Add 2 drops of distilled water to each tube, then heat the tubes in a boiling water bath.
8. Centrifuge the tubes. Record observations on your data sheet.
9. For tubes without precipitates, continue to step 10. For tubes with precipitate, continue to step 11.
10. Add concentrated HCl and record your observations. Add Na2CrO4 and record your observations. Discard to waste.
11. Add two drops of NH3 solution to each tube. Test the acidity of each solution by dipping a clean stirring rod into the liquid and touching it to the litmus paper. If a solution is acidic it will turn the blue litmus paper red. If a solution is basic it will turn the red litmus paper blue. If your solutions are not basic, add more NH3 until they turn red litmus blue.
12. Centrifuge the tubes. Record observations on your data sheet.
13. Decant the tubes that have solids, but instead of decanting to waste, decant into a clean tube. Add 3M HCl to the three solutions until acidic (turns blue litmus red). Record observations.
14. Add a drop of sodium chromate to each tube. Note the colors of the precipitates.
15. Discard all the solutions and solids to waste. Rinse all tubes with water and discard to waste
1. Each student will test 3 unknowns and report the ions present in each sample. To practice, choose the trial unknown, do the experiments as you did for the knowns, and click check your answer. A flowchart is provided on the simulation site and here to help you work through the process. When you are confident you can use the experiments to determine what ions are present in your unknowns, proceed.
2. Select your first assigned unknown number. Your assigned unknown numbers will be provided by your Instructor.
3. Complete steps 1-8.
4. If no precipitate forms, continue to step 10.
5. If a precipitate forms, decant the supernatant into a different test and add 3 M HCl. Test the acidity of the supernatant by dipping a clean stirring rod into the liquid and touching it to the blue litmus paper to make sure it is acidic. Add a drop of sodium chromate to the test tube and record any observation/s.
6. The test tube that contains the precipitate, continue with steps 11 - 15.
7. Complete the data sheet and submit your data sheet with post lab questions to the appropriate dropbox.
unknown number is 293
Can someone please help me with this lab?