Periodicity and Chemical Reactivity - Weebly



Periodicity and Chemical Reactivity

Introduction

The periodic table can be used to predict the physical and chemical properties of elements and their compounds. This laboratory activity investigates two properties as functions of an element’s location within a family on the Periodic Table. You will work with compounds of Group 2, the alkaline earth family, to determine the variation and the pattern in the solubility and reactivity within the family.

Purpose To observe the results of reactions involving Group 2 metal ions and determine a pattern of reactivity of the elements of the family.

Equipment/Materials The van will provide all materials.

3, 24 well microplates dropper bottles containing:

black paper Mg2+ solution Na2SO4 solution

distilled water Ca2+ solution Na2C2O4 solution

thin-stemmed pipets Sr2+ solution Na2CO3 solution

q-tips (for cleaning wellplates) Ba 2+ solution

Safety:

• Always wear goggles and aprons in the lab.

• Take care not to get solutions on skin. Wash immediately if you do.

Procedure

Part 1:

1. Place a microplate on a piece of black paper. The letters should be along the left side and the numbers along the top.

2. Place exactly 10 drops of the Mg2+ solution in well A1, 10 drops of Ca2+ solution in well B1, 10 drops of Sr2+ solution in well C1, and 10 drops of Ba2+ solution in well D1. Be sure to hole the dropper bottles at the same angle each time so that the drop sizes are uniform.

3. Add 5 drops of distilled water to each of the wells 2-6 in rows A-D.

4. Use a thin-stemmed pipet to transfer 5 drops of liquid from A1 to A2. Be sure that the other 5 drops of liquid stay in well A1.

5. After transferring the liquid, use the thin-stemmed pipet to mix the solution in A2 well.

6. Transfer 5 drops of the liquid in A2 to A3 and mix well.

7. Continue transferring 5 drops to the next well and mixing through well A6.

8. Remove 5 drops of liquid from well A6 and discard. All wells A1-A6 should have 5 drops of liquid remaining in them.

9. Repeat steps 4 through 8 for rows B, C, and D.

10. Add 5 drops of sodium sulfate (Na2SO4) solution to each well and record “Yes” for any observed reactions in Data Table 1.

Part 2:

11. Repeat steps 2 through 9 in the 2nd well plate

12. Add 5 drops of sodium oxalate (Na2C2O4) solution to each well and observe any reactions.

13. Record “Yes” for any observed reactions in Data Table 2.

Part 3:

14. Repeat steps 2 through 9 above in the 3rd well plate

15. Add 5 drops of sodium carbonate (Na2CO3) solution to each well and observe any reactions.

16. Record “Yes” for any observed reactions in Data Table 3.

17. When you have finished recording your results and answered all questions THEN you can wash out all 3 well plates and clean up your equipment.

PERIODICITY AND CHEMICAL REACTIVITY

Data Table

Name(s): _________________________________

Data Table 1: Reactions of Group II Metal Ions with Sulfate Ions

| |1 |2 |3 |4 |5 |6 |

| | | | | | | |

|Mg2+ | | | | | | |

| | | | | | | |

|Ca2+ | | | | | | |

| | | | | | | |

|Sr2+ | | | | | | |

| | | | | | | |

|Ba2+ | | | | | | |

Data Table 2: Reactions of Group II Metal Ions with Oxalate Ions

| |1 |2 |3 |4 |5 |6 |

| | | | | | | |

|Mg2+ | | | | | | |

| | | | | | | |

|Ca2+ | | | | | | |

| | | | | | | |

|Sr2+ | | | | | | |

| | | | | | | |

|Ba2+ | | | | | | |

Data Table 3: Reactions with Group II Metal Ions with Carbonate Ions

| |1 |2 |3 |4 |5 |6 |

| | | | | | | |

|Mg2+ | | | | | | |

| | | | | | | |

|Ca2+ | | | | | | |

| | | | | | | |

|Sr2+ | | | | | | |

| | | | | | | |

|Ba2+ | | | | | | |

Questions:

1. What pattern can you describe for the precipitation of the sulfate ions?

2. What pattern can you describe for the precipitation of the oxalate ions?

3. What pattern can you describe for the precipitation of the carbonate ions?

4. From the data and observations recorded in your data tables, determine which of the salts – Mg, Ca, Sr, or Ba – is the most soluble.

5. Which of the salts is least soluble?

6. How are the reactivity tendencies observed with the sulfate and Group 2 ions supported by the reactions with oxalate and carbonate ions? (In other words, are the patterns similar with respect to the Group 2 ions?)

7. Write a general statement of your conclusions concerning the relative reactivities of Group 2 ions.

8. Write balanced equations for the reactions.

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