1.11: Experiment_611_Periodic Properties_2_0
- Page ID
- 303073
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Student Name |
Laboratory Date: Date Report Submitted: |
___________________________ |
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Student ID |
Experiment Number and Title |
Experiment 611: Periodic Properties |
Experiment 611: Periodic Properties
Section 1: Purpose and Summary
- Carry out reactions involving Group 2 cations and Group 17 halides.
- Identify an unknown solution based on the properties observed for the ions.
NOTE: Some older textbooks use prior group designations of Group 2A and Group 7A. We will be using the current designations of Group 2 (Be, Mg, Ca, Sr, Ba, Ra) and Group 17 (F, Cl, Br, I, At). Note that Be, Ra and At are not included in this experiment.
In this experiment, students will conduct a series of reactions involving some alkaline earth metal ions and halide ions. Students will determine observable trends and characteristic reactions within each group. Using the information gathered, students will determine the elements present in an unknown solution.
Section 2: Safety Precautions and Waste Disposal
Safety Precautions:
Use of eye protection is recommended for all experimental procedures.
Silver nitrate (AgNO3) solutions will react with skin and leave brown stains. Avoid direct contact with silver nitrate solutions. Contact may not be seen until after exposure to direct sunlight.
Sodium fluoride solutions will react with glass and should not have long term contact with glass (short time periods with dilute solutions are not generally a problem).
Waste Disposal:
While you are doing the experiment, collect your reaction mixture into a waste beaker.
When you are finished with the experiment, pour the contents of the waste beaker into the inorganic waste container in the fume hood.
Section 3: Procedure
Part 1: Reactions involving Group 2 cations
Transfer about 5 mL each of Mg(NO3)2, Ca(NO3)2, Sr(NO3)2, and Ba(NO3)2 solutions into four (4) labeled large test tubes. The NO3- ion is a spectator ion in the solution; hence, will not interfere with any of the reactions.
Label four (4) small test tubes with Mg2+, Ca2+, Sr2+, and Ba2+ for use in each test reaction below. The test tubes must be cleaned and rinsed with laboratory water between tests. They do not have to be dried.
Note: All reactions below are double displacement reactions. Observe whether or not precipitate forms. If no reaction is observed, write ‘no reaction’.
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(a) Add about 10 drops each of the metal ion solutions into the labeled small test tubes. (b) To each test tube, add about 10 drops of 0.25 M (NH4)2C2O4. Mix the contents thoroughly. (c) Record your observations in the data table below, including the color of the precipitate formed. (d) Discard reaction mixtures in a designated waste beaker. |
(a) Add about 10 drops each of the metal ion solutions into the labeled small test tubes. (b) To each test tube, add about 10 drops of 1 M NaBrO3. Mix the contents thoroughly. (c) Record your observations in the data table below, including the color of the precipitate formed. (d) Discard reaction mixtures in a designated waste beaker. |
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H2SO4 |
NaOH |
(NH4)2C2O4 |
NaBrO3 |
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Mg2+ |
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Ca2+ |
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Sr2+ |
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Ba2+ |
Part 2. Reactions involving Group 17 halides
Transfer about 1 mL each of NaF, NaCl, NaBr, and NaI solutions into four (4) labeled test tubes. These solutions should all be at 0.1 M for concentration. The Na+ ion is a spectator ion in the solution; hence, will not interfere with any of the reactions.
Label four (4) small test tubes with F-, Cl-, Br- and I- for use in each test reaction below. The test tubes must be cleaned and rinsed with laboratory water between tests. They do not have to be dried.
The reaction of the halides with silver ion is a precipitation reaction. Observe whether or not precipitate forms. Cloudiness is due to the formation of fine suspended solid particles in solution. If no reaction is observed, write ‘no reaction’.
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The reaction with chlorine water with a halide ion is an example of a redox reaction. Chlorine removes an electron from the halide ion and converts these ions to the diatomic halogens. The halide ions are colorless in solution. Bromine water and iodine water, on the other hand, are colored in solution. Observe the color changes in the following reaction.
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AgNO3 |
Cl2× H2O |
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F- |
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Cl- |
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Br- |
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I- |
Part 3: Identification of Unknown
Obtain an unknown solution from your instructor and record the identification code. This unknown solution is a solution of a Group 2 halide or a nitrate compound in water (for example, MgCl2, CaBr2, etc.). Perform each of the tests done in Parts 1 and 2, record your observations in the data table below. Based on these observations, identify the ions that may be present in your unknown solution, then write its chemical formula and name.
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Test Reaction |
Observation |
Possible identity(ies) of the ion |
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Group 2 cation |
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(a) with H2SO4 |
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(b) with NaOH |
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(c) with (NH4)2C2O4 |
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(d) with NaBrO3 |
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Group 17 halide |
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(a) with AgNO3 |
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(b) with Cl2×H2O |
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Identification code of unknown |
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Identity of the unknown |
Chemical Formula Name |
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Post-lab Question:
Write the net ionic equation for each reaction that occurred in this experiment. There is no need to write an equation for reaction mixtures recorded with ‘no reaction’.
Notes: